IEC 62368-1: Ask the Engineers, Question-and-Answer Page

Does a Class II cord-connected product investigated to UL 62368-1 and that is intended to be supplied by standard 15A or 20A outlet need to employ a polarized-type attachment plug?

More specifically, you asked (edited for clarity): Is a polarized plug mandatory for a paper shredder based on UL 62368-1? I found it’s a requirement in UL 60335 or UL 60950, but it’s not stated in UL 62368-1.

In response, UL 62368-1, Annex DVA (Clause G.4.2), stipulates that a Class II product that employs a single pole disconnect device is to be provided with a polarized plug-type attachment plug. This requirement is a national difference from IEC 62368-1 and is driven by the National Electrical Code (NEC). It is the same requirement that was in UL 60950-1. So, polarization is not required for all Class II constructions.

As this forum is not intended to analyze and provide guidance on specific designs, we recommend that you contact UL Solutions and request an in-depth consultation if you have a specific design or construction that you would like to discuss.

Is an AV/ICT product employing a terminal block for AC mains permanent connection without a wiring compartment eligible for the UL Listing Mark?

More specifically you asked (edited for clarity): We design a switch product that has a permanently connected terminal block with three terminals: Line, Neutral and Protective Earth. The switch is rated 100-240 Vac. If we plan to have the switch evaluated as a complete unit (UL Listing Mark) for connection to AC mains, the user manual defines the proper installation, including installation of our product in a suitable Listed cabinet. The wiring compartment is not provided by us. Can this construction be UL Listed?

In response, in order for an AV/ICT product intended for permanent connection to an AC Mains to be considered eligible for applying a UL Listing Mark, all related requirements in CSA UL 62368-1 are to be met, including Annex DVH, Permanently connected equipment – mains connections, which generally requires that the wiring compartment shall be provided. (There is an exception for equipment connected to DC Mains and installed in a Restricted Access Area.) If the wiring compartment is not provided, the product can be considered eligible for the UL Recognition Mark as it would rely on an end product to satisfy the permanent connection safeguard requirements of Annex DVH and Annex G.7.6, Supply wiring space.

As this forum is not intended to analyze and provide guidance on specific designs, we recommend that you contact UL Solutions and request an in-depth consultation if you have a specific design or construction that you would like to discuss.

For UL 62368-1 certification, if a PE symbol (per IEC 60417-5019) is marked next to the protective earthing terminal of a terminal block used for a permanent connection, does the PE terminal screw or nut additionally need to be green in color?

More specifically you asked (edited for clarity): We design networking routers meeting UL 62368-1. We have a permanently connected equipment (supply type) using a terminal block which has three terminals Line, Neutral and Protective Earth. The supply is DC MAINS. The protective EARTH or ground terminal is marked with PE Symbol as per IEC 60417. If this symbol is there, do we also need a green color nut or screw? (This PE terminal is covered by a cover, so is not visible and only the PE mark per IEC 60417 can be seen.)

In response, the protective earth terminal screw or nut does not need to be additionally green in color if the IEC 60417-5019 symbol is provided next to the PE terminal. The IEC 60417-5019 PE symbol marking next to the earthing terminal is sufficient to indicate that the terminal is intended for the protective earthing conductor.

In UL 62368-1, these considerations, including use of green color for PE, are based on the requirements in the National Electrical Code (NEC). For details, and additional considerations on visibility, please see Annex DVH (normative) – Permanently connected equipment – mains connections, and its requirements in DVH.5.1, Identification of protective earthing terminal, which states, “If the terminal is not visible, the conductor entrance hole shall be marked with the word “green” or “ground,” the letters “G” or “GR,” or the grounding symbol (IEC 60417, No. 5019), or otherwise identified by a distinctive green colour.” Therefore, the described construction appears to meet the intent of this NEC-driven requirement in UL 62368-1.

As this forum is not intended to analyze and provide guidance on specific designs, we recommend that you contact UL Solutions and request an in-depth consultation if you have a specific design or construction that you would like to discuss.

How to determine PS classification for a passive loudspeaker with no power source (power amplifier) provided, just a rated maximum power handling capacity?

More specifically you asked (modified for clarity): Regarding Power Source (PS) classification, how are you supposed to perform measurements on equipment that does not contain a defined power circuit and is delivered without one, such as a passive speaker? The speaker may have a rated power handling capacity, but the actual details of the power circuit (amplifier) are unknown and will most probably vary in later use. For a worst-case fault in the load, the maximum delivered power is dependent on the specifications and behavior of the power amp.

In response, to assess a passive loudspeaker that does not have a specific power source, reliance is placed on the information, including recommendations and ratings, provided by the manufacturer.

Although sub-clause F.3.3.2, Equipment without direct connection to mains, of IEC 62368-1 does not require equipment without direct connection to mains to have an electrical rating, it is standard industry practice for passive loudspeakers to have information or a rating related to power handling capacity. For lack of other details, this information can be used to establish a PS level classification for a passive loudspeaker, along with any other relevant information provided by the manufacturer.

For classifying part of an overall system for PS, although imperfect, this approach is relatively consistent with the general information in sub-clause 6.2.2.1 of IEC 62368-1:2018.

However, it should be noted that IEC 62368-1:2023 includes numerous changes related to loudspeaker drivers and loudspeaker driver assemblies that were incorporated, in part, due to some of the challenges classifying loudspeaker drivers and assemblies that your question introduces. In fact, most of the safeguards against risk of electrical fire in Clause 6 of the latest edition have exceptions for loudspeaker drivers and loudspeaker driver assemblies due to their unique design requirements and the lack of adverse field incident data, which also is consistent with past practice under IEC 60065. Therefore, PS classification of loudspeaker drivers and assemblies is less important under IEC 62368-1:2023.

As this forum is not intended to analyze and provide guidance on specific designs, we recommend that you contact UL Solutions and request an in-depth consultation if you have a specific design or construction you would like to discuss.

For a product evaluation to one edition of IEC 62368-1, is it acceptable to use a power supply in the product to an earlier edition?

More specifically you asked (edited for clarity): For a product evaluation and an IECEE CB Test Report/Certificate to IEC 62368-1 3rd edition, is it acceptable to use a power supply only evaluated to and having an IECEE CB Test Report/Certificate to IEC 62368-1 2nd edition? How about for the US, UL 62368-1, and European, EN 62368-1 3rd edition? Is it acceptable to use a power supply evaluated to UL 62368-1 2nd edition and EN 62368-1 2nd edition?

A specific IEC 62368-1 edition has published requirements to demonstrate compliance with that specific edition. There are no provisions in the Standard itself for considering earlier editions, unless stated as a specific requirement. In general, the way these situations are usually handled is, if a manufacturer wants to use a power supply to a previous edition of the Standard other than the edition being used for the end product, then there will need to be a determination (investigation) made as part of the end product investigation to determine that the power supply investigated (certified) to the earlier edition can be shown to comply with the latter edition. This can be relatively straightforward, or complex, depending on the specific power supply and end product. (Often it is easier to change the power supply and use one that complies with the latest edition, thus the component power supply industry often is the first sector to update their component certifications to the latest edition.) This approach is used for EN 62368-1 and CSA UL 62368-1, and the IECEE CB Scheme. To help with these challenges UL Solutions has published Certification Impact Analyses for IEC 62368-1 (and previously IEC 60950-1) for over 20 years to assist understanding what specific changes have been made from one edition to the next, which help aid determine what additionally might need to be considered.

The complete answer to this topic can be complex, and there appears to be a specific, detailed construction that needs review/analysis. Therefore, you are encouraged to contact UL Solutions for an in-depth engineering engagement.

If our server comes with slide-rails in the box, but can be fitted to any rack, do I have to perform slide-rail mounted equipment testing?

Yes, if the server is provided with slide rails as a possible mounting means, regardless of whether the slide rails are attached at the manufacturing facility, or they are provided in the box for shipment, IEC 62368-1, Sub-Clause 8.11 testing of the mounting rails for slide-rail mounted equipment (SRME) is applicable, unless the product is an MS1 energy source as defined in Table 35 of IEC 62368-1. The Mounting means for rack mounted equipment testing is intended to evaluate the suitability of the mounting hardware, regardless of what rack it is installed in. If a rack is not part of the supplied system, then testing of the SRME with slide-rails is conducted on a representative rack/system.

What is defined as a 'suitable coating' in IEC 62368-1? Is a standard solder mask considered to be a suitable coating?

More specifically your asked: I can't find a proper definition of a 'coated board' in the 62368-1 standard. What is defined as a 'suitable coating'? Is a standard solder mask considered to be a suitable coating?

In response, there is no definition of a “coated board” or “suitable coating” in Clause 3 of IEC 62368-1:2023, the latest edition, or earlier editions. However, in relation to ‘suitable coating’, sub-clause G.13.3 of Annex G of IEC 62368-1 states the following:

“For printed boards whose outer surfaces are to be coated with a suitable coating material, the minimum separation distances of Table G.13 apply to conductive parts before they are coated.”

For application purposes, it is generally understood in IEC 62368-1 that a coated printed board that meets tests of G.13.6 of IEC 62368-1 is considered a printed board coated with a suitable coating material covered in G.13.3. Generally, a standard solder mask would not be considered a suitable coating material unless it complied with the test specified in G.13.6. However, even if a solder mask complies with G.13.6, it only would allow for reduction of Clearances and Creepage distances across the conductor pattern, which is different than a traditional conformal coating, which also may cover component leads, etc.

Also note that an alternative method to qualify coated printed boards is given in IEC 60664-3, which IEC 62368-1 permits per G.13.3.

Additionally, in the U.S. and Canada, compliance of a conformal coating with the UL 746 series is considered as an acceptable alternative to IEC 60664-3 according to Annex DVF (G.13.6) of CSA UL 62368-1.

Information on ULS Recognized Component Conformal Coatings can be located in the UL category, QMJU2, Coatings for Use on Recognized Printed Wiring Boards – Component. Please see UL Product iQ for additional information. Use of a conformal coating in accordance with QMJU2 needs to be utilized in accordance with its conditions of acceptability and ratings.

Note too, QMJU2 has additional information on the difference between a Resist coating (solder mask) and Conformal coating. Please see below. Under QMJU2, a Resist coating is only tested for flammability, not as insulation, so it would not fulfill the requirements in G.13.3 of CSA UL IEC 62368-1.

“Resist coating, also known as solder resist or solder mask, is a material supplied in liquid or film form used to mask or to protect selected areas of a conductor pattern from the action of an etchant, solder, or plating, and remains on the printed wiring board after processing. Resist coatings have been tested for flammability with regards to the specific laminate and/or UL/ANSI type material indicated in the individual Recognition.

Conformal coating is an insulating protective coating that conforms to the configuration of the object coated, is applied on the completed board assembly to increase the dielectric voltage withstand capability between conductors and protects against environmental conditions. Conformal coatings are used on printed wiring boards in electrical equipment where electrical spacings are insufficient between uninsulated live parts of opposite polarity or between such parts and accessible dead-metal parts. Conformal coatings have been tested for flammability and dielectric properties (with regard to the effect of environmental, humidity and thermal conditions) for the specific laminate and/or UL/ANSI type material indicated in the individual Recognition. The environmental, humidity and thermal conditions are intended to emulate the end-use application.”

What is the current UL Solutions participation on IEC TC108 and its National Committees?

UL Solutions is well represented on the National Committees for IEC TC108, in addition to the TC108 Hazard-Based Standard Development Team (HBSDT), plus we continue to fulfill the IEC TC108 (and US NC TAG) Secretary function. This commitment to the AV/ICT industry and international standards development helps provide UL Solutions with important insight into the latest developments associated with IEC 62368-1 and all the TC108 standards. It also provides us with a solid understanding of the principles on which these standards are built, which today is increasingly important as UL Solutions is a global leader providing compliance engineering and knowledge services worldwide to AV/ICT manufacturers.

UL Solutions’ current IEC TC108 Team (as of 4Q 2023) includes:

• IEC TC108 Management - Valara Davis (Secretary, UL Standards & Engagement); Grace Roh (Asst. Secretary, UL Standards & Engagement)
• Denmark: National Committee TC108 - Jan Jensen (Chair and HBSDT Expert); Marshal Zhang (HBSDT Expert)
• Germany: National Committee TC108 - Roland Koehler (Chair and HBSDT Expert)
• Italy: National Committee TC108 - Isaia Bonavoglia (Expert)
• Japan: National Committee TC108 - Ikuro Kinno (HBSDT Expert); Shoichi Nezu (HBSDT Expert)
• Korea: National Committee TC108 – DongSeok Lee (Expert)
• U.K.: National Committee TC108 - Paul Lovell (Chair)
• U.S.: National Committee (ANSI TAG) TC108: Grace Roh (Secretary – UL Standards & Engagement); Thomas Burke (Principal - HBSDT Expert, Interpretation Panel; Editing Committee); Todd Bonfanti (HBSDT Expert); Karen Reddington (HBSDT Expert); Hai Jiang, PhD (Electric Shock Expert); Edward Lin (HBSDT Expert)

How can I as a manufacturer get involved with IEC TC108, the IEC technical committee that produces IEC 62368-1, IEC TR 62368-2, IEC 62368-3, IEC 60990 and related documents?

Participation on IEC TC108 is via National Committees. Therefore, the most available method to get involved in the work of IEC TC108 is through your National Committee for the country in which you are located. As a national committee member, you receive TC108 documents and proposals, and you collaborate with your fellow National Committee members to provide a consensus national response on such proposals.

Currently (4Q 2023), there are 26 participating (P) countries and 14 observing (O) countries associated with IEC TC108.

The IEC maintains a Dashboard (web area) for each IEC TC - see link below. If interested in joining your national committee, there is contact information for each national committee in the membership area of the dashboard.

Note that each national committee is run per their own country-specific rules and there likely will be a fee to join and participate on your national committee.

In the U.S., UL Standards & Engagement is the Secretary of the ANSI USNC Technical Activity Group (TAG) for IEC TC108, so you can contact ULSE if you want more information sent to you about membership. For other countries, a simple inquiry made to the Secretary of the National Committee for your country likely will get you moving in the right direction. 

http://www.iec.ch/dyn/www/f?p=103:29:5827964972015::::FSP_ORG_ID,FSP_LANG_ID:1311,25 

I am interested in joining IEC TC108 and assisting with the development of IEC 62368-1 - how can I do this?

Experts / Manufacturers generally do not join the IEC Technical Committees independently.  Typically, a Manufacturer should first join their National Committee (NC) for IEC and begin getting involved participating in their National Committee.  National Committee members receive IEC TC108 documents, can propose comments/revisions (if the NC supports them), and can participate in their National Committee voting. Please note, most National Committees will have an associated monetary fee to participate.

Subsequently, as an NC member, if the NC Member is interested, the Member can request to join as an Expert the IEC TC maintenance teams, new work project teams, etc., including the Hazard Based Standard Development Team, which does the primary work maintaining IEC 62368-1, producing documents for NC review and voting. All formal approval of documents is via National Committee voting.

Therefore, we recommend that you contact the National Committee that represents your country if your country participates on IEC TC108 - https://www.iec.ch/dyn/www/f?p=103:29:717472019271837::::FSP_ORG_ID,FSP_LANG_ID:1311,25.

 In the US, the associated TC108 committee is the ANSI US NC / Technical Advisory Group (TAG) for IEC TC108 - https://www.ansi.org/usnc-iec/usnc-overview. As UL Standard and Engagement is the Secretary of the US TAG TC108, you can contact ULSE for additional information on joining the US TAG TC108 - https://62368-ul-solutions.com/contact-ul.html.

Does UL Standards and Engagement plan to publish a UL 62368-3 Standard based on IEC 62368-3:2017?

For those unaware, the first edition of IEC 62368-3 was published in 2017, and has the title, Audio/video, information and communication technology equipment - Part 3: Safety aspects for DC power transfer through communication cables and ports. It addresses two key topics. 

Clause 5 covers power transfer using ES1 and ES2 voltages. USB and PoE are examples of the technologies covered.

Clause 6 covers power transfer using RFT, or Remote (Power) Feeding Telecommunications circuits. Clause 6 essentially covers the same circuits / technologies as originally covered in the legacy standard, IEC 60950-21, Remote Power Feeding.

For more background on IEC 62368-3, please review UL Solutions IEC 62368-3 Backgrounder.

When the CAN US Technical Harmonization Committee (THC) reviewed both IEC 62368-1:2018 and IEC 62368-3:2017 for potential adoption in Canada and the U.S., a decision was made to develop and propose a CAN US version of the IEC 62368-1:2018 standard, which subsequently was published on December 13, 2019 as CSA UL 62368-1:2019 (Ed. 3). However, during this review the THC also made a decision not to pursue a CAN US version of IEC 62368-3.

The decision not to pursue a CAN US version of IEC 62368-3 was made because the THC believed IEC 62368-3 requires some refinement before it would be an appropriate standard for adoption as a mandatory bi-national standard for Canada and the U.S. This refinement was thought needed both for its Clause 5 and its Clause 6. Therefore, rather than adopt IEC 62368-3, the THC proposed, and eventually got accepted the following National Difference in Clause 1 of CSA UL 62368-1, Ed. 3.

“1DV.2.3 Additional requirements for equipment with DC power transfer through communication cables and ports are given in IEC 62368-3. IEC 62368-3 clause 5 for DC power transfer at ES1 or ES2 voltage levels is considered informative. IEC 62368-3 clause 6 for remote power feeding telecommunication (RFT) circuits is considered normative (see ITU K.50). Alternatively, equipment with RFT circuits are given in either UL 2391 or CSA UL 60950-21. RFT-C circuits are not permitted unless the RFT-C circuit complies with RFT-V limits (<= 200V per conductor to earth).”

Therefore, in Canada and the U.S., USB, PoE and similar circuits will not be required to be investigated to Clause 5 (in addition to 62368-1). However, RFT circuits will continue to need additional evaluation beyond 62368-1 per the options allowed for in the National Difference 1DV.2.3.

Note, within IEC TC108 there are two projects open to replace IEC 62368-3 Clause 5 with a new IEC 63315 and Clause 6 with a new IEC 63316, both of which will be Group safety publications.

Clause 0 Principles of this product safety standard

Why is HBSE (Hazard-Based Safety Engineering) called the future of product safety?

Hazard-based safety engineering (HBSE) offers a new perspective on product safety. HBSE principles permeate the new IEC 62368-1 safety standard, and are primarily performance-based, rather than prescriptive. Fewer prescriptive requirements means you don’t need to wait so often for standards to catch up with innovation. A hazard-based standard devoid of prescriptive construction requirements and containing only performance-oriented requirements to determine the effectiveness of required safeguards means that a higher level of flexibility now exists for product designers as product technologies and constructions continue to evolve.

Clause 1 Scope

Can UL 62368-1 be used to certify/list Modular Data Centers (MDCs) in the United States?

The short answer is, no.

In the U.S., modular data centers, or MDCs, are installed in accordance with NFPA 70, the National Electrical Code (NEC).

In fact, in the 2014 NEC, a new Article 646, Modular Data Centers, was added specifically to cover MDCs. So, any jurisdiction (state or otherwise) in the U.S. that has adopted the 2014 NEC (or later) will require the MDC to be installed per NEC Article 646.

A MDC is defined in the NEC as a Prefabricated unit, rated 1000 volts or less, consisting of an outer enclosure housing multiple racks or cabinets of information technology equipment (ITE) (e.g., servers) and various support equipment, such as electrical service and distribution equipment, HVAC systems, and the like.

Thus, Article 646 covers, or points to requirements for electrical supply and distribution, HVAC, lighting / emergency lighting, IT/ITC equipment, and other aspects.

While via an Informational Note in the Article it acknowledges UL 62368-1 as the appropriate standard for certification of the actual IT/ICT equipment installed in a MDC, UL 62368-1 does not cover MDCs under its scope, nor does it address the key support equipment mentioned above also found in a typical MDC.

What Article 646 does acknowledge (in 646.4) is that MDCs that are listed and labeled in compliance with UL Subject 2755, Outline of Investigation for Modular Data Centers, only require specific, limited areas of Article 646 to be applied to them in addition. This is because UL Subject 2755 is aligned with the requirements in Article 646 and covers many of the MDC construction elements not found in UL 62368-1, including requirements for the support equipment.

UL Solutions offers listing and labeling to UL Subject 2755 under our PQVA equipment category.

Clause 1 Scope

Can passive loudspeakers be evaluated to IEC 62368-1?

More specifically, you asked (edited for clarity): We currently evaluate powered loudspeakers (i.e., internal amplifier, connections to AC Mains, etc.) to IEC 62368-1. However, how are passive loudspeakers evaluated when the powered component is removed (i.e., no connection to AC Mains, no internal amplifier, etc.)?

In response, passive loudspeakers can be submitted for investigation to IEC 62368-1 as a sub-assembly, or as part of a speaker system that is able to connect to other speakers or to an amplifier source. Test conditions for these applications can be complex and require the certifier to work closely with the manufacturer on the configurations for the loudspeaker system based on the associated specifications, ratings, etc. Then, depending on the stated configurations, specific IEC 62368-1 requirements can be applied.

Special focus should also be directed to Clause 5 (Electrically caused injury) as its ES classification can be an important factor when evaluating loudspeakers.

Also noted is that IEC 62368-1:2023 (Edition 4) has extensive revisions addressing amplifiers and loudspeakers, both in Clause 6 (Electrically caused fire), which has revised enclosure requirements for loudspeaker drivers and assemblies, and Annex E (Tests conditions for equipment containing audio amplifiers), which was revised extensively to make a more appropriate set of test conditions for modern amplifier designs without adding new requirements.

As this forum is not intended to analyze and provide guidance on specific designs, we recommend that you contact UL Solutions and request an in-depth consultation if you have a specific design or construction that you would like to discuss.

Clause 1 Scope

Is outdoor AV/ICT equipment covered by (UL EN) IEC 62368-1?

In IEC 62368-1:2014, the scope (Cl 1) referenced IEC 60950-22 for AV/ICT equipment that may be installed outdoors.

However, as of Edition 3 (IEC 62368-1:2018), the requirements for outdoor AV/ICT equipment are incorporated into the Part 1 Standard, and there will not be a separate Part 2 standard like there was for IEC 60950.

Annex Y (Construction requirements for outdoor enclosures) contains most of the requirements found previously in IEC 60950-22, but other clauses also incorporate some requirements, such as Clause 5 and voltage limit considerations for accessible contact of potentially wet parts.

The current editions of EN IEC 62368-1 and CSA UL 62368-1 are structured similarly.

Clause 1 Scope

In relation to UL 1449, does UL IEC 62368-1 cover surge protectors?

Since the question was not clear, we will address both, does UL IEC 62368-1 cover certification of surge protectors and, does UL IEC 62368-1 require component surge protectors to comply with UL 1449?

In response, UL IEC 62368-1 does not cover certification of surge protectors. Surge protectors, including component devices (e.g., individual varistors) and cord-connected surge protective devices for general use applications, typically are certified under either the component or Listing category for surge protective devices (VZCA or VZCA2) using UL 1449, Surge Protective Devices. UL 62368-1 has a National Difference (1DV.5.1.4) in its scope redirecting to UL 1449 for cord-connected surge protective devices for general use applications. However, UL IEC 62368-1 with its National Differences can cover power distribution units (PDUs) with surge protective devices for AV/ICT applications, such as in data centers.

For component surge protectors used in AV/ICT equipment certified to UL IEC 62368-1, the component requirements for surge protective devices are described in Annex G.8, Varistors. Annex G.8 states that varistors shall comply with IEC 61051-2 or IEC 61643-331. However, in UL 62368-1’s Annex DVE (G.8), covering mandatory US and CSA component requirements, a National Difference states that surge protective devices complying with UL 1449 (typically VZCA2) shall be used when such devices require a rating below 250 V (such as connected to typical 120V/240V mains).

As this forum is not intended to analyze and provide guidance on specific designs, we recommend that you contact UL Solutions and request an in-depth consultation if you have a specific design or construction that you would like to discuss.

Clause 1 Scope

Does the IEC 62368-1 standard cover lead-acid batteries?

In response, since there are no product details provided with your question, including what type of lead-acid batteries (e.g., VRLA, flooded, etc.) are used and what type of AV/ICT equipment will the batteries be installed within, the response to your inquiry will rely mainly on quoting the requirements in IEC 62368-1:2018 that address AV/ICT equipment with lead-acid batteries.

However, first, the simple answer to your question is, yes, IEC 62368-1:2018 (and IEC 62368-1:2023) covers AV/ICT equipment containing lead-acid batteries.

On the component level, lead-acid batteries used in AV/ICT equipment should comply with the applicable component standards noted in Annex M.2, such as IEC 60896-11 (Stationary Lead Acid Batteries – Part 11 – Vented type); IEC 60896-21 (Stationary Lead Acid Batteries – Part 21 – Valve regulated type – method of test); IEC 61056-1(General purpose lead-acid batteries (valve-regulated types) – Part 1: General requirements, functional characteristics – Methods of test); and IEC 61056-2 (General purpose lead-acid batteries (valve-regulated types) – Part 2: Dimensions, terminals and marking).

Table 17, Safety of batteries and their cells - requirements (expanded information on documents and scope), of IEC TR 62368-2, Audio/video, information and communication technology equipment – Part 2: Explanatory information related to IEC 62368-1:2018, provides a good overview of the standards in Annex M.2 that cover lead-acid batteries.

On the equipment level, the requirements for equipment with lead-acid batteries are included in the following Annex M sub-clauses: (a) Annex M.3 - protection circuits for batteries provided within the equipment; (b) Annex M.5 – risk of burn due to short-circuit during carrying; (c) Annex M.6 – safeguard against short-circuits; (d) Annex M.7 – risk of explosion from lead acid and NiCd batteries; (e) Annex M.8 – protection against internal ignition from external spark sources of rechargeable batteries with aqueous electrolyte; (f) Annex M.9 – preventing electrolyte spillage; and (g) Annex M.10 – instructions to prevent reasonably foreseeable misuse.

Due to the limited information in your question, only a general response has been able to be provided to your inquiry. However, we encourage you to contact UL Solutions for an in-depth consultation related to specific applications that involve use of lead-acid batteries in AV/ICT equipment.

Clause 4 General requirements

Do Suppliers of components (actives and passives) to power supply manufacturers and equipment manufacturers need to certify to 62368-1 and what are those tests required?

Your question seems to be related to general component requirements and supply chain transition plans to IEC 62368-1, which would be challenging to fully answer / explain in this sort of Q&A forum. 

However, the component requirements in IEC 62368-1 usually are specified in Annex G, Components, although there are a few special components that have their own Annex, like Annex J, for multi-layer insulated winding wire.

Components in 62368-1 generally are considered several different ways. They need to either:

• comply with a specified IEC component standard (e.g., X/Y capacitors, fuses, varistor, switches, etc.), which generally need certification to the IEC component standard; or
• comply with the IEC 62368-1 requirements (e.g., motors, IC Current Limiters, etc.), usually included as a performance test program in Annex G; or
• comply with either a specified IEC component standard specified in Annex G or a test program in Annex G (e.g., transformers, opto-coupler, etc.).

If a component is listed in Annex G, generally it is preferable that the component manufacturer achieve component certification to allow for pre-selection by the end product manufacturer.  The component certification is either by certification to the IEC component standard, if a standard other than IEC 62368-1 is specified (e.g., X or Y capacitor), or by certification to IEC 62368-1 (e.g., IC Current Limiter).

If IEC 62368-1 does not specifically reference an IEC component program or an Annex G performance program, then the component generally can be investigated as part of the equipment without any special investigation (i.e., does not require individual certification) – this applies to most passives, including resistors, electrolytic and film capacitors (non- X & Y), inductors, transistors, etc. not used as a safeguard.

In the U.S. and Canada there are specific component requirements for some components, which are contained in Annexes DVE, DVF & DVG. For example, printed circuit boards associated with ES 2/ 3 and PS 2/ 3 circuits need to comply with UL 796.

For detailed requirements for components, please review Annexes G, DVE, DVF & DVG, and we encouraged you to contact UL Solutions for an in-depth consultation via https://www.ul.com/services/iec-62368-1-testing-certification.

Clause 4 General requirements

Do Suppliers of components (actives and passives) to power supply manufacturers and equipment manufacturers need to certify to 62368-1 and what are those tests required?

Your question seems to be related to general component requirements and supply chain transition plans to IEC 62368-1, which would be challenging to fully answer / explain in this sort of Q&A forum. 

However, the component requirements in IEC 62368-1 usually are specified in Annex G, Components, although there are a few special components that have their own Annex, like Annex J, for multi-layer insulated winding wire.

Components in 62368-1 generally are considered several different ways. They need to either:

• comply with a specified IEC component standard (e.g., X/Y capacitors, fuses, varistor, switches, etc.), which generally need certification to the IEC component standard; or
• comply with the IEC 62368-1 requirements (e.g., motors, IC Current Limiters, etc.), usually included as a performance test program in Annex G; or
• comply with either a specified IEC component standard specified in Annex G or a test program in Annex G (e.g., transformers, opto-coupler, etc.).

If a component is listed in Annex G, generally it is preferable that the component manufacturer achieve component certification to allow for pre-selection by the end product manufacturer.  The component certification is either by certification to the IEC component standard, if a standard other than IEC 62368-1 is specified (e.g., X or Y capacitor), or by certification to IEC 62368-1 (e.g., IC Current Limiter).

If IEC 62368-1 does not specifically reference an IEC component program or an Annex G performance program, then the component generally can be investigated as part of the equipment without any special investigation (i.e., does not require individual certification) – this applies to most passives, including resistors, electrolytic and film capacitors (non- X & Y), inductors, transistors, etc. not used as a safeguard.

In the U.S. and Canada there are specific component requirements for some components, which are contained in Annexes DVE, DVF & DVG. For example, printed circuit boards associated with ES 2/ 3 and PS 2/ 3 circuits need to comply with UL 796.

For detailed requirements for components, please review Annexes G, DVE, DVF & DVG, and we encouraged you to contact UL Solutions for an in-depth consultation via https://www.ul.com/services/iec-62368-1-testing-certification.

Clause 4 General requirements

For a product evaluation to one edition of IEC 62368-1, is it acceptable to use a power supply in the product to an earlier edition?

More specifically you asked (edited for clarity): For a product evaluation and an IECEE CB Test Report/Certificate to IEC 62368-1 3rd edition, is it acceptable to use a power supply only evaluated to and having an IECEE CB Test Report/Certificate to IEC 62368-1 2nd edition? How about for the US, UL 62368-1, and European, EN 62368-1 3rd edition? Is it acceptable to use a power supply evaluated to UL 62368-1 2nd edition and EN 62368-1 2nd edition?

A specific IEC 62368-1 edition has published requirements to demonstrate compliance with that specific edition. There are no provisions in the Standard itself for considering earlier editions, unless stated as a specific requirement. In general, the way these situations are usually handled is, if a manufacturer wants to use a power supply to a previous edition of the Standard other than the edition being used for the end product, then there will need to be a determination (investigation) made as part of the end product investigation to determine that the power supply investigated (certified) to the earlier edition can be shown to comply with the latter edition. This can be relatively straightforward, or complex, depending on the specific power supply and end product. (Often it is easier to change the power supply and use one that complies with the latest edition, thus the component power supply industry often is the first sector to update their component certifications to the latest edition.) This approach is used for EN 62368-1 and CSA UL 62368-1, and the IECEE CB Scheme. To help with these challenges UL Solutions has published Certification Impact Analyses for IEC 62368-1 (and previously IEC 60950-1) for over 20 years to assist understanding what specific changes have been made from one edition to the next, which help aid determine what additionally might need to be considered.

The complete answer to this topic can be complex, and there appears to be a specific, detailed construction that needs review/analysis. Therefore, you are encouraged to contact UL Solutions for an in-depth engineering engagement.

Clause 4 General requirements

Can an IEC 62368-1 power supply adapter (QQJQ) be used in place of a UL 1310 Class 2 adapter (EPBU)?

In response, the answer to the question really depends on the end product system.

If the application is an AV/ICT system for US/Canada Listing, a QQJQ adapter (power supply) would be acceptable in place of a EPBU adapter (power supply). Although Annex DVG, UL and CSA component requirements (alternative), of UL 62368-1 permits UL 1310 Adapters in place of UL 62368-1 Adapters, it is common practice to use QQJQ adapters compliant with UL 62368-1 in AV/ICT systems investigated to UL 62368-1.

Note, an Adapter complying with IEC 62368-1 only (e.g., with IECEE CB Report/Certificate) would not be acceptable without additional determination of compliance with U.S. National Differences, along with coverage under UL Solutions Follow-up Service.

If the end product application is not an AV/ICT system, then the decision on acceptance of a QQJQ Adapter in place of a EPBU Adapter would need to be made per the applicable end product standard and the stated requirements within. UL 62368-1 covers adapters for AV/ICT applications and not all end product standards would accept a device intended for such applications.

As this forum is not intended to analyze and provide guidance on specific designs, we recommend that you contact UL Solutions and request an in-depth consultation if you have a specific design or construction that you would like to discuss.

Clause 4 General requirements

What are the requirements for internal and external wiring according to IEC 62368-1, Ed. 3, and UL 62368-1, Ed. 3?

More specifically, you asked: I am seeking product certification to IEC 62368 and have come up against the wire flammability issue. I note the existing answer regarding equivalence with VW-1, but what about superior standards such as CL2? Is there a means by which CL2 being superior — i.e., the NEC® allows substitution — to VW-1 allows me to demonstrate compliance with UL 62368, the Standard for Audio/Video, Information and Communication Technology Equipment?

In response, as you inferred, the note under Subclause 6.5, “Internal and external wiring” in IEC 62368-1, Ed. 3, as well as UL 62368-1 accepts VW-1 wires rated to UL 2556, the Standard for Wire and Cable Test Methods, to demonstrate compliance with 6.5.1 as an alternative method.

In addition, for external wiring, according to the U.S./CAN deviations under 4.1.17DV.1, “External interconnecting cable and wiring,” such wiring is to be investigated to the requirements of 6.5 and either 4.1.17DV.1.2 or 4.1.17DV.1.3, depending on the cable length.

External interconnecting cable and wiring 3.05 m or less may be investigated as part of the equipment (system) to the requirements of this standard, depending on the PS circuits involved:

• External interconnecting cable and wiring connected to PS2 or PS3 circuits — the flammability requirement of 6.5 applies.
• There are no flammability requirements for external interconnecting cable and wiring in PS1 circuits.

Other external interconnecting cables and wiring exceeding 3.05 m in length are required to comply with 4.1.17DV.1.3, including the references to the Canadian Electrical Code, Part I, CSA C22.1; and the National Electrical Code® (NEC®), NFPA 70®, under Annex DVA (Annex Q), where CL2 Listed cables are allowed to be used in Class 2 and LPS circuits.

Such CL2 cables are UL Listed as Power Limited Circuit Cable (QPTZ), information for which can be found in UL Product iQ®.

Please note: CL2 cables are subjected to a vertical-tray flame test in UL 1685, the Standard for Vertical-Tray Fire-Propagation and Smoke-Release Test for Electrical and Optical-Fiber Cables, which is a more onerous test than VW-1. Therefore, if a manufacturer wanted to also substitute Listed CL2 cables for internal wiring or external cabling not exceeding 3.05m in length, that would be considered acceptable, too, as long as the circuit was Class 2 or LPS. However, most manufacturers choose not to do so due to cost considerations.

The complete answer to this topic is complex, and there appears to be a specific, detailed construction that needs review/analysis. Therefore, we encourage you to contact UL Solutions for an in-depth consultation.

Clause 5 Electrically-caused injury

Must the tolerance associated with a Gas Discharge Tube (GDT) specification for insulation breakdown be considered per sub-clause 5.5.7.2 in IEC 62368-1:2014?

More specifically you asked: As per Clause 5.5.7.2 of 62368-1, Ed. 2, GDT shall meet the electric strength test of 5.4.9.1 for basic insulation. When identifying a specific GDT which has Hi-Pot properties, do we have also to consider its tolerance, so that its value plus its negative tolerance is greater than the value of basic insulation?

In response, 5.5.7.2 of IEC 62368-1:2014 mainly applies to where an SPD (Surge Protective Device) is used between the mains and protective earth, and it covers a varistor and a GDT (Gas Discharge Tube) connected in series with two specific criteria.

For the varistor, it is required to comply with Annex G.8 for the consideration of safeguards against electric shock and fire. For the GDT, both the electric strength test per 5.4.9.1 and the external clearance and creepage distance requirement per 5.4.2 and 5.4.3 respectively for basic insulation are required.

In the case of the application of the electric strength test per 5.4.9.1 to the GDT, it relies fully on a type testing procedure on the GDT alone. Therefore, the informative tolerance listed in the GDT specification for the insulation breakdown is not required to be a formal part of the compliance check. Even if the relative ratings plus their negative tolerances result in the worst specification greater than the required test voltage for basic insulation for the application, the electric strength test per 5.4.9.1 as stated in 5.5.7.2 is the specific compliance criteria to be considered in IEC 62368-1.

The complete answer to this topic is complex, and there appears to be a specific, detailed construction that needs review/analysis. Therefore, you are encouraged to contact UL Solutions for an in-depth consultation via https://www.ul.com/services/iec-62368-1-testing-certification.

Clause 5 Electrically-caused injury

Why do the IEC 62368-1 Table 17 Creepage Distance working voltages start at 10V RMS for Basic Insulation when 10V is ES1 and does not require a Creepage Distance?

The spacings tables in clause 5.4 provide clearance and creepage distance values for the specified voltages regardless of ES energy classification. These values are based on the IEC 60664 series insulation coordination standards. The need to apply minimum clearance and creepage distances within ES1 circuits depends on the specific requirement being applied. For example, clause B.4.4, Functional Insulation, is an example of when such spacings would be considered within ES1 circuits as one option.

As this forum is not intended to analyze and provide guidance on specific designs, we recommend that you contact UL Solutions and request an in-depth consultation if you have a specific design or construction that you would like to discuss.

Clause 5 Electrically-caused injury

For a DC power supply of 48V input, is it necessary to list X capacitors connected across the input in the critical component list (CCL) - if yes then what is the safety aspect of listing them?

In response, since 48Vdc is classified as ES1 when any related tolerances of the supply circuit are less than 60Vdc, the criteria in Table 4 for ES1 would be met. In such a case no further safeguard would be required for such X capacitors, and 5.5.2.1 and G.11 would not apply. Therefore, such X capacitors should not need to be listed in the CCL in most cases.

As there appears to be a specific, detailed construction that needs review / analysis that may not be obvious from the details in the question (e.g., if specified tolerances were greater than 60Vdc, and therefore the requirements and limits in clause 5.5.2.2, Safeguards against capacitor discharge after disconnection of a connector, also may need to be considered), you are encouraged to contact UL Solutions for an in-depth consultation via https://www.ul.com/services/iec-62368-1-testing-certification.

Clause 5 Electrically-caused injury

For a DC power supply of 48V input, is it necessary to list X capacitors connected across the input in the critical component list (CCL) - if yes then what is the safety aspect of listing them?

In response, since 48Vdc is classified as ES1 when any related tolerances of the supply circuit are less than 60Vdc, the criteria in Table 4 for ES1 would be met. In such a case no further safeguard would be required for such X capacitors, and 5.5.2.1 and G.11 would not apply. Therefore, such X capacitors should not need to be listed in the CCL in most cases.

As there appears to be a specific, detailed construction that needs review / analysis that may not be obvious from the details in the question (e.g., if specified tolerances were greater than 60Vdc, and therefore the requirements and limits in clause 5.5.2.2, Safeguards against capacitor discharge after disconnection of a connector, also may need to be considered), you are encouraged to contact UL Solutions for an in-depth consultation via https://www.ul.com/services/iec-62368-1-testing-certification.

Clause 5 Electrically-caused injury

Is an Ethernet connection considered an external circuit? If yes, what ID is it considered from Table 13 - External circuit transient voltages and associated transient voltages?

Although there is more than one type of Ethernet, Ethernet networks do meet the definition of an External Circuit (3.3.1.1 in IEC 62368-1:2018; 3.3.1.2 in IEC 62368-1:2023), i.e., “electrical circuit that is external to the equipment and is not MAINS.” In an IEC 62368-1 context, there is no limitation on external circuits being associated exclusively with outdoor locations as the definition also includes indoor locations.

Table 13 assigns expected transient voltages to external circuits. However, Table 13 is in transition between IEC 62368-1:2018 and IEC 62368-1:2023.

In IEC 62368-1:2018, Ethernet circuits would be considered ID 1 (Paired conductor a – shielded or unshielded), which has an associated 1500 V, 10/700 µs transient voltage. However, if the equipment manufacturer expects the Ethernet network that the equipment is connected to will be maintained completely within the building structure, the first condition to Table 13 allows for, “In general, for EXTERNAL CIRCUITS installed wholly within the same building structure, transients are not taken into account.” The equipment manufacturer would need to specify the expected installation condition (connected to in-building Ethernet only) for the equipment in the equipment’s installation instructions, which would be documented in the associated certification report.

In IEC 62368-1:2023 there has been significant modification/restructuring of Table 13 to align it with changes planned for the IEC TC108 Technical Report, IEC TR 62102, Electrical safety – Classification of interfaces for equipment to be connected to information and communications technology networks, which is the reference document for classifying ICT network interfaces.

In IEC 62368-1:2023, if the equipment could be connected to an Ethernet network located outdoors, the network interface expected for the equipment would be considered ID 1a, “Symmetrical paired conductors – shielded or single ended paired or unpaired conductors – outdoor aerial or buried exposure (for example, outdoor telecommunications cables).” The associated transient voltage is 1500 V, 10/700 μs, same as IEC 62368-1:2018.

However, if the same equipment would only involve interconnection with an Ethernet network located wholly indoors, the network interface expected for the equipment would be considered ID 1b, “Symmetrical paired conductors or single ended paired or unpaired conductors – shielded or unshielded, typically short outdoor or stays within a structure. Typically less than 300 m.” The associated transient voltage is 1500 V, 1.2/50 μs. During the research/work by IEC TC108 on the pending changes to IEC TR 62102, consensus was reached that even Ethernet networks wholly installed within a building do have transient voltages associated with them, thus the change from past editions now reflected in IEC 62368-1:2023.

Clause 5 Electrically-caused injury

How is ES class evaluated for a DC to DC switching power supply? Can a measured voltage determine ES class when DC is supplied?

More specifically you asked (edited for clarity): How to evaluate ES class associated with a DC to DC switching power supply? It seems not suitable to test its touch current because, according to 5.7.2, it is based on IEC 60990, which mainly covers AC distributed power. if DC supplied, do we only measure voltage to determine ES class?

In response, electrical energy source (ES) classifications are determined by voltage or current according to sub-clause 5.2. Table 4 defines the ES limits for steady state voltage and current. It’s applied for both AC and DC. Also, footnote “c” states, “For sinusoidal waveforms and DC, the current may be measured using a 2 000 Ω resistor.”

If DC output voltage exceeds ES1 limit (60V), then current should be measured using a 2 k Ω resistor, but compliance with both voltage limits and current limits is not required. Note also that ES1 is defined when the measured value does not exceed ES1 limits under normal, abnormal operating and single fault conditions (or when not exceeding ES2 limits under single fault conditions of a Basic or Supplementary Safeguard).

Related to applicability of IEC 60990 to DC, although most of the example supply circuits in IEC 60990 are AC, the Scope (1) of IEC 60990 covers, “…measurement methods for - d.c. or a.c. current of sinusoidal or non-sinusoidal waveform, which could flow through the human body…,” and “…is applicable to all classes of EQUIPMENT, according to IEC 61140.” IEC 61140 covers both AC and DC systems. However, as stated above, IEC 62368-1, Table 4, footnote “c” allows use of a 2 000 Ω resistor rather than an IEC 60990 network for DC and sinusoidal AC. For simplicity, a 2 000 Ω resistor typically is used for DC touch current measurements.

When DC-DC converters are involved, the evaluation and classification is not limited to the voltage levels of the circuit supplying the converter - the working voltages and frequency generated within the converter also need to be considered. For example, when accessible circuits are required to be ES1 due to some accessibility requirements in the final application, the entire system and its circuits must be analyzed by construction review and, when required, by measurement and tests, such as Working Voltage Measurement and Single Fault Condition (SFC), to demonstrate that the ES1 circuits are not compromised by higher ES2 or ES3 voltages generated within the converter. Investigation and test may show that additional Safeguards are required.

With reference to sub-clauses 4.2.3 and 4.2.4, it also is important to note that the standard allows manufacturers to declare higher class than there is in the product. (For example, if an energy source class 3 is declared by the manufacturer, there is no need to conduct any ES1 or ES2 measurements, assuming ES1 is not required because of accessibility.)

Also, specifically related to switch-mode power supplies, as an ES classification is based on working voltage and/or touch current, it is worth noting that voltages (due to switch-mode conversion) may be generated that exceed the ES1 limit even if the input to the supply is ES1. Therefore, detailed evaluation and tests typically are needed for such switch-mode conversion circuits, even for DC-DC converters. However, for most converters, such as 5V input to 3.3V or 1 Vdc output, typical switching voltages are not expected to exceed ES1 limits under normal, anormal or single fault conditions.

Clause 5 Electrically-caused injury

What is the appropriate electrical insulation between AC mains circuits and the unearthed parts of USB ports of Class I equipment, and how to identify whether USB ports are accessible or inaccessible?

More specifically you asked (edited for clarity): For Class I equipment, Basic Insulation should be applied between AC input (ES3) and Grounded metal enclosure, and Reinforced Insulation should be applied between AC input (ES3) to unearthed ES1 conductors or circuits (e.g., USB port +5Vdc power rail since it cannot meet protective bonding requirements). However, there is a high probability of a failure when you apply the 4000Vdc (Reinforced Insulation) Hi-pot test between AC input and USB port +5Vdc power lead, even though the 2500Vdc (Basic Insulation) Hi-pot already passed between AC input and Enclosure since most designed-in spacings between +5Vdc and GND are very close (5-10mils). (Basic Insulation + Functional Insulation is not equivalent to Reinforced Insulation.) How do I understand and address this requirement? Is there any different assessment/requirement when the USB port is accessible versus inaccessible?

In response, when considering electrical insulation between mains and external circuits (classified per sub-clause 3.3.1.1 of IEC 62368-1:2018), if unknown devices can be connected to the external circuits, the external circuits should be considered accessible because it is assumed that users may access the circuits in the unknown devices. Therefore, all conductive pins of USB connectors should be classified as accessible when applying the electrical insulation requirements in IEC 62368-1.

Regarding electric strength (Hi-pot) testing, we note that generally it is only applied to solid insulation investigated to sub-clause 5.4.4, although it is permitted as an alternative method to also meet some Clearance requirements per sub-clause 5.4.2. Also, in accordance with sub-clause 5.4.9.1, “For equipment incorporating basic insulation and supplementary insulation in parallel with reinforced insulation, care is taken that the voltage applied to the reinforced insulation does not overstress basic insulation or supplementary insulation.” Therefore, generally, the electric strength test should not be applied to a complete system of Basic, Supplementary and Reinforced insulation, but should be applied separately to each individual insulation.

If applied to the complete system, and the electric strength tests reveal insulation breakdown, root causes could include insufficient safeguards or overstressed Basic or Supplementary Insulation (breakdown through the parallel path). In this situation, insulation should be individually tested and insulation that is not being specifically tested may be disconnected and separately tested according to sub-clause 5.4.9.1 of IEC 62368-1:2018. In your case, only insulation defined as Reinforced Insulation should be subjected to the electric strength testing for Reinforced Insulation.

As this forum is not intended to analyze and provide guidance on specific designs, we suggest that you contact UL Solutions requesting an engineering engagement if you have a specific design or construction that you would like to discuss.

Clause 5 Electrically-caused injury

How is a Clearance determined when the working frequency is above 30 kHz for a switch mode power supply according to IEC 62368-1:2018?

More specifically you asked (Edited): In Edition 3, for determining a clearance, Table 10 should be used for the switching frequencies not exceeding 30 kHz and Table 11 for those exceeding 30 kHz. Since most power supplies would generate switching frequencies greater than 30 kHz, Table 11 is necessary to follow. For an overvoltage category II, PD 2, Material Group III, this value jumps from 1.27 mm in Table 10 and to 13.2 mm in Table 11 for > 30kHz. Please let me know if my understanding is correct. Also please confirm, whether these "switching frequencies" are of the "mains voltage" or of the "working voltage" of the power supply? Primary? Secondary?

In response, for determining Clearances per 5.4.2, the highest value of two procedures is used. Your question is specifically related to Procedure 1, determining Clearances according to 5.4.2.2, which considers the highest voltage of either the Working Voltage (across the Clearance), Recurring Peak Voltages, and the Temporary Overvoltage.

More specifically, the highest voltage is used to determine the Clearance, using Table 10 for circuits with fundamental frequencies up to 30 kHz, Table 11 for circuits with fundamental frequencies higher than 30 kHz, and both Tables 10 and 11 for circuits where both frequencies lower and higher than 30 kHz are present.

When Table 10 applies, the temporary overvoltage 2000V should be considered, and for the conditions you stipulated, we confirm a 1.27 mm Clearance would be the resulting minimum Clerance for basic or supplementary insulation.

When Table 11 applies, which is only applicable for those voltages with working frequencies higher than 30 kHz, the voltage associated with the switching frequency generated from pulse-width modulation (PWM) in the primary circuit of the power supply should be applied rather than a temporary overvoltage, which does not have a frequency higher than 30 kHz.

Therefore, the clearance result you indicated of 13.2 mm (based on a temporary overvoltage value of 2000V used in Table 11) would be incorrect. Generally, most applications of switch mode power supplies would result in a peak working voltage in the primary circuit not exceeding 1000 V, resulting in a Clearance from Table 11 of 0.6 mm for basic or supplementary insulation.

However, the highest clearance values of Table 10 and Table 11 should be chosen for circuits where both frequencies lower than 30 kHz and higher than 30 kHz are present in Procedure 1. Therefore, the result from Table 10, 1.27 mm Clearance would be the highest for the Procedure 1. However, values per Procedure 2 also need to be considered as part of the final determination.

We expect you would find very helpful subclause 5.4.2 of IEC TR 62368-2:2019, which is the Technical Report (TR) containing explanatory information on IEC 62368-1 and is often known as the ‘Rationale Document.’ This sub-clause 5.4.2 contains a very good flowchart / worked example on the application of the Clearance requirements.

Clause 5 Electrically-caused injury

What are the differences in application of the electric strength test in power supplies and end products?

More specifically, you asked: A PSU certified to IEC 60950-1 passes the HIPOT test at 2121 V DC between primary and earth. When it is used in an end product to be certified to IEC 62368-1, does it need to withstand the end product HIPOT test that could be more than 2121 V DC, e.g., 2500 V DC?

Generally, no, as a type test. Per Subclause 4.1.1 of IEC 62368-1, components complying with IEC 60950-1 are acceptable without further evaluation other than to consider the appropriate use of the component in the end product.

Therefore, while there is the need to determine the necessity of an electric strength (HIPOT) test as a type test per 5.4.9.1 on the end product if the end product contains any solid insulation designated basic, supplementary or reinforced insulation, solid insulation in the PSU complying with the relevant requirements of IEC 60950-1 is not required to be reassessed via type test and brought into compliance with IEC 62368-1.

Please note that the electric strength test per 5.4.9.1 of 62368-1 is the type test for solid insulation. Therefore, the test requirements do not generally apply to insulation through the air, i.e., gaps complying with clearance and creepage distance requirements. There is no general HIPOT test at 2121 V DC between PRI and earth that is performed as a type test in 62368-1, although there typically is a production line (routine) test (at reduced ES test values) required per (EN) IEC 62911, Audio, Video and Information Technology Equipment – Routine Electrical Safety Testing in Production, and as a certification requirement of individual certifiers, including UL Solutions. These production line tests typically check for gross manufacturing defects, including miswiring errors, rather than rechecking all specific insulation properties originally qualified via type tests.

The IEC TC108 interpretation panel question of 108/698/INF provides guidance for component acceptance per 4.1.1 with some examples in various situations. Although this particular question was not addressed exactly, it will be helpful for further understanding of the application of 4.1.1, and the document is available through the IECEE website.

Clause 5 Electrically-caused injury

I calculated the clearances according to 5.4.2.1 and got the highest value according to Procedure 1. Now I want to find the test voltage from Table 16. Can I use 5.4.2.3.2.5 for decreasing the required withstand voltage to get lower test voltage?

All references are to the published IEC 62368-1: 2014, unless otherwise indicated.

You indicated that you calculated the clearances according to 5.4.2.1 and got the highest value according to Procedure 1. Then you indicate you want to find the test voltage from Table 16.

Please note, per 5.4.2.1, to determine the Clearance, the highest value of the two procedures is used, Procedures 1 and 2.

Table 16 is associated with 5.4.2.4 Determining the adequacy of a clearance using an electric strength test. Sub-clause 5.4.2.4 is part of Procedure 2 (the alternative approach if Procedure 2 is larger than Procedure 1).

However, since you indicated you already got the highest value according to Procedure 1, there is no need to use Procedure 2 and 5.4.2.4 (Clearance per Procedure 1 + ES). You can use Procedure 1 without Electric Strength.

Please look at the flowchart in 5.4.2 of IEC TR 62368-2, Explanatory information related to IEC 62368-1. It illustrates nicely the relationship between Procedures 1 & 2.

Note, you also reference 5.4.2.3.2.5, Determining transient voltage levels by measurement,  but this sub-clause only is used if you do not want to use the assumed transient voltages per Table 13. It is not used for withstand voltage.

Clause 5 Electrically-caused injury

What's the definition for "Pulse" in IEC 62368-1?

A pulse is not specifically defined in IEC 62368-1. However, as noted in the standard, it can either be a voltage or current waveform that has maximum peak value depending on the test and condition when it is measured (i.e., normal, abnormal or single fault). A pulse may last from a fraction of second up to a few seconds. It can also be single or repetitive with off periods in between. (For switch mode power supplies (SMPS), sometimes pulses are associated with what some call “hiccup” mode.) Compliance with different requirements in Clause 5 generally will depend on pulse durations and off periods.

Also, keep in mind too, the use of the term “pulse” in IEC 62368-1 parallels use of the same undefined term in the legacy standard, IEC 60950-1. Sub-clause 2.2 of IEC 60950-1, including Figs. 2E.1 and 2E.2, contains some graphical representations of what are considered pulses.

Clause 5 Electrically-caused injury

Why did UL 62368 not use UL 101 method ("e" is always open) to measure touch current? What's the background?

UL 62368-1 is harmonized with IEC 62368-1.  As an electronic standard it utilizes the leading information on assessment of electric shock.  As part of this it follows the testing protocol of IEC 60990, Methods of measurement of touch current and protective conductor current.

62368-1 also considers risk to a person under normal, abnormal and single fault conditions.  This is a basic principle within the Standard.  In line with this philosophy, IEC 60990 considers the various faults possible based on power distribution system (single phase, 3 phase Delta, etc.) and power systems, e.g., TN, TT, etc.

An aid is available to all users of IEC 62368-1, it is the technical report IEC TR 62368-2, Explanatory information related to IEC 62368-1:2018.  Within this document it explains how hazard-based engineering was followed and  resulted in the development of the requirements.  The document can be purchased through your regular standard acquisition channels.

In addition to the rationale document, there are a number of technical papers available on the development of IEC 60990 and its principles.

Clause 5 Electrically-caused injury

For AV/ICT equipment intended to be installed outdoors, is the 30Vdc limit for accessible parts from 60950-22 applicable, or do we apply touch current requirements as in IEC 62368-1 table 4?

More specifically you asked (edited for clarity): I have a question regarding interpretation of touch current requirements for outdoor equipment per IEC 60950-22. Per sub-clause 6.1 of 60950-22 the requirements are based on voltage limits only for example 30Vdc max under normal conditions. There seems to be no touch current requirements specified here. Now in IEC 62368-1 Ed. 3, with IEC 60950-22 requirements now included the standard, it basically does not specify any touch current requirements specific to wet locations but applies only the table 4 in 62368-1 from my understanding. Looking further, in IEC TR 62368-2:2019, the following statement exists on voltage limits with no limits indicated: "For outdoor equipment, lower voltage limits apply because the body impedance is reduced to half the value when subjected to wet conditions as described in IEC TS 60479-1 and IEC TS 61201." Question: Do we have to still follow the 30Vdc requirements as in 60950-22, or stick to the hazard-based approach & apply touch current requirements as in IEC 62368-1 Table 4? I saw a 60950-22 to 62368-1 Ed. 3 clause mapping document made by UL Solutions but it seems to be unclear on this topic.

In response, we would like to first make note that IEC 60950-22, and it's requirements for outdoor equipment, have been incorporated directly into IEC 62368-1 as of IEC 62368-1:2018 (Edition 3). Specifically, related to accessible circuits, see sub-clause 5.3.2.1, Accessibility to electrical energy sources and safeguards - Requirements, which states,

“For bare parts of outdoor equipment that are accessible to an ordinary person in their intended outdoor location, the following shall not be accessible:

• bare parts exceeding 0,5 times ES1 voltage limits under normal operating conditions and abnormal operating conditions and single fault conditions of a component, device or insulation not serving as a safeguard; and
• bare parts exceeding ES1 voltage limits under single fault conditions of a basic safeguard or of a supplementary safeguard (see 5.2.1.1).”

Therefore, for accessible circuits of outdoor equipment that do not exceed 0.5 ES1 voltage limits, such as 30Vdc for dc circuits, there is no need to take additional current measurements. For such accessible circuits that exceed 0.5 ES1 voltage limits, then the normal current limits for ES1 cannot be exceeded, but they are not halved. They are not halved because, while in the case of voltage the voltage limits need to consider reduced body impedance due to the wet conditions as part of the process of deriving effect of actual current, in the case of current, the measured current itself is the energy source directly associated with the physiological risk of electric shock, so it is not halved. (The same was true for the application of IEC 60950-22: the SELV voltage limits were halved for outdoor applications, but if these were exceeded, the LCC (Limited Current Circuit) limits were not halved.)

Clause 5 Electrically-caused injury

Must external protective earthing conductors be provided with Class I permanently connected equipment powered by DC mains, or may on-site installation of such PE conductors be required by user documentation?

More specifically you asked: For permanently connected equipment powered by DC mains, using an external protective earthing conductor: Is the manufacturer expected to provide this protective earthing conductor as part of the equipment or can the specifications and/or use of such a conductor be stated in the user documentation?

There is a variety of equipment types powered by DC mains, so we cannot answer your question in great specificity in this public Q&A platform. Therefore, you are encouraged to contact UL Solutions for an in-depth consultation via https://www.ul.com/services/iec-62368-1-testing-certification.

However, in general, yes, permanently connected equipment may have a protective earthing conductor that is installed in the field by skilled persons (electricians).

Such field wiring can consist of both line conductors and PE conductor(s). Electricians who install the equipment will provide suitable wiring materials necessary for the supply and PE connections in accordance with the installation instructions associated with the equipment (and in accordance with national/local electrical codes). However, proper interface with the electrical system (mains) is required as part of the equipment, which includes not only instructions, but also proper terminal sizes, etc.

In IEC 62368-1:2018, appropriate requirements primarily are in sub-clause 5.6, Protective Conductor. Equipment can either be shipped with the appropriate PE conductor(s) complying with the relevant requirements in sub-clause 5.6, or be provided with installation instructions so that the installers can select proper wiring material for the field installation.

In CSA UL 62368-1, appropriate National Differences that reflect the US and Canadian electrical codes are in Regulatory Annex DVA, 5.6, including the provision that “Equipment intended to be connected to a nominal 48 V d.c. (or higher) power supply source, or systems rated less than 48 V d.c. that have one point directly earthed (grounded), shall have provision for the earthing (grounding) of all exposed dead metal parts that might become energized from the power supply source or from circuits involving a risk of electric shock.” Additional National Differences are in Annex DVH, Requirements for permanent connection, and associated Marking and Instruction requirements are in Annex DVK.

Clause 5 Electrically-caused injury

How do the requirements in sub-clause 5.4.11, which requires external circuits to be separated from earth in 'normal' pluggable equipment type A, apply to the shield of an external cable? Can the shield be connected to earth?

Per the IEC TR 62368-2 entry for 5.4.11, the original intent of these requirements was to prevent communication system workers outside the building from being injured if there was a fault inside the building between mains and earth and the equipment had an external circuit extending from it to a communications network outside the building.  If communications workers were working on communications circuits outside the building, they could be injured if adequate safeguards were not in place. Therefore, per 5.4.11 and Table 13 (of IEC 62368-1:2018), the requirement only applies to Table 13 ID No. 1.

In considering the requirement in sub-clause 5.4.11 of IEC 62368-1:2018, we need to remember that an external circuit is a circuit external to (outside) the equipment, but not all external circuits extend outside the building.

Per your question, it is not clear if the subject circuit is an (a) an external circuit extending outside the building, thus obviously covered by Table 13 ID No. 1 (e.g., telecommunication circuit), or (b) an external circuit installed wholly within the same building structure (e.g., some PoE).

If (a), and the installation instructions / instructional safeguards require that the shield is to be connected to protective earth at the equipment and outside the building, the shield would be part of the protective earthing scheme.  However, if the shield is connected to protective earth through the equipment, the equipment shall meet either the 4 dashed paragraph in 5.4.11.1.

If (a), and the installation instructions do not require the shield to be connected to protective earth, then the shield should be considered similarly to the other external circuits extending outside the building.

If (b), and the external circuit is “installed wholly within the same building structure” (see first condition to Table 13), then the cable is not a true ID No. 1, and the current view is that 5.4.11 requirements are not applicable. (There is no indication in IEC TR 62368-2 that the intent of IEC TC108 was to extend the application of 5.4.11 to PoE and other external circuits wholly inside the building that may utilize paired / twisted pair conductors.)

We note that these requirements have been updated in IEC 62368-1:2023.

Clause 5 Electrically-caused injury

Does pluggable type B equipment with an Ethernet port need to be provided with a permanently connected protective earthing conductor to comply with the requirements in Sub-clause 5.6.7?

More specifically you asked (edited for clarity): In sub-clause 5.6.7, whether pluggable equipment type B is considered to have reliable earthing seems to depend on if it connects to external circuits ID 1 to 5. Would pluggable type B equipment with an Ethernet port need to have provision for a permanently connected protective earthing conductor to comply? Is it of any significance if, (1) the Ethernet connector shield is or is not connected to earth in the equipment?; (2) the equipment does or does not have varistors connected directly between mains and earth?; (3) the Ethernet, or other external circuits ID 1 to 5, do or don't extend outside the building?

In response, the intention of sub-clause 5.6.7 is that it only is to be considered when other sub-clauses in IEC 62368-1:2018 require reliable earthing and reference 5.6.7 for requirements. Sub-clause 5.6.7 does not establish when reliable earthing is required since that determination is made by other sub-clauses which reference 5.6.7. Therefore, whether AV/ICT with an Ethernet port requires reliable earthing is not based on sub-clause 5.6.7, but by other sub-clauses.

If another sub-clause requires reliable earthing and references 5.6.7, and the subject equipment is Pluggable Type B (or even Pluggable A) with circuits considered Table 13, ID numbers 1, 2, 3, 4 or 5, then 5.6.7 requires a permanently connected Protective Earthing Conductor (separate from the earthing associated with the plug), with instructions for the installation of that separate conductor to the building earth by a Skilled Person. However, please also note that most Ethernet ports with paired conductor cabling are not considered IDs 1 or 2 (per Table 13) subjected to transients if the cable is not intended (by installation instructions or similar) to be routed outside the building. (See first condition of Table 13.) 

We note that these requirements have been updated in IEC 62368-1:2023.

The complete answer to this topic is complex, and there appears to be a specific, detailed construction that needs review/analysis. Therefore, you are encouraged to contact UL Solutions for an in-depth consultation via https://www.ul.com/services/iec-62368-1-testing-certification.

Clause 5 Electrically-caused injury

I want to know more about Clearance and Creepage Distance measurements involving peak voltages above 330V - what actually would the limits be for a PSU with either a 240 Vrms or 48V Dc powered?

Your question is related to the fundamental application of IEC 62368-1’s Clearance and Creepage Distance requirements, which would be challenging to fully answer / explain in this sort of Q&A forum. Therefore, we recommend that you contact UL Solutions offline ( https://www.ul.com/services/iec-62368-1-testing-certification ) for a more detailed engineering engagement.

However, in general, subclauses 5.4.2 and 5.4.3 in IEC 62368-1:2014, or the same subclauses in IEC 62368-1:2018, are used to determine the required minimum clearances and creepage distances. Moreover, new for the application of IEC 62368-1:2018, for overvoltage category II, clearances in circuits connected to an AC mains not exceeding 420V peak (300V rms) may be determined per Annex X as an alternative. Annex X is similar to subclause 2.10.3.3 in IEC 60950-1:2009+A2:2013.

Using a switch mode power supply as an example, for IEC 62368-1:2018 to determine the required minimum clearance and creepage distance for basic and reinforced (insulation) safeguard, the following parameters need to be taken into account: overvoltage category, pollution degree, material group, declared operational altitude, and working voltage frequency, in addition to the peak and r.m.s working voltages.

(Although your product may be rated 240 Vrms, that is not the voltage typically used to investigate the significant insulation safeguards in SMPSs. Please see 5.4.2.2 for some of the details why.)

Also, although the procedures in subclause 5.4.2 are somewhat complex, in many cases they allow for smaller clearances than permitted by Annex X.

We expect you would find very helpful subclause 5.4.2 of IEC TR 62368-2:2019, which is Technical Report containing explanatory information on IEC 62368-1, often known as the “Rationale Document.” This sub-clause 5.4.2 contains a very good flowchart / worked example on the application of the Clearance requirements, which many new users of IEC 62368-1 find very helpful.

Clause 5 Electrically-caused injury

Does UL 62368-1 allow use of a green colour insulation for a protective bonding conductor?

More specifically you asked: In sub-clause 5.6.2.2 (Colour of insulation), can protective bonding conductors be insulated with a green colour (not green-and-yellow) except for the two cases in this sub-clause? I know that protective earthing conductor could be insulated with a green colour according to the National Difference in UL 62368-1 in G.7. How about protective bonding conductor?

In response, sub-clause 5.6.2.2 requires green-and-yellow for the insulation of both protective earthing conductor(s) and protective bonding conductor(s). The green (only) colour of insulation only is permitted in the protective earthing conductor of power cord sets in North America. As you stated, this requirement is in Annex DVE (G.7) of UL 62368-1.

Since a protective bonding conductor is defined per 3.3.11.9 in UL 62368-1:2019 (3.3.11.8 in UL 62368-1:2014) as being located in an equipment, it is not a part of the power supply cord. Thus, the insulation of the protective bonding conductor is not covered by Annex DVE (G.7) and is required to be green-and-yellow, except for the two cases indicated in sub-clause 5.6.2.2 accordingly.

Clause 5 Electrically-caused injury

Does UL 62368-1 allow for a solid green colored bonding conductor?

More specifically you asked: Does UL 62368-1 allow use of a green colour insulation for a protective bonding conductor? The product has a detachable cord set, complying with UL 817 - must the protective bonding conductor in the cord also be green and yellow? How to evaluate when the bonding conductor is totally inside the cord?

In response, the protective earthed conductor in a detachable power supply cord is considered a protective earthing conductor and not a protective bonding conductor.

Based on sub-clause 5.6.2.2, the protective bonding conductor shall be green-and-yellow. 

As a CAN US National Difference, cord sets and power supply cords may employ a "solid green" protective earthing conductor according to Annex DVE, G.7.

For protective bonding conductors in general, 5.6.2.2 states that for a protective bonding conductor the color also shall be green-and-yellow except for two cases specified in 5.6.2.2.

Clause 5 Electrically-caused injury

For determining Clearances, is it allowed to reduce mains transients by using either external or internal surge protection devices?

More specifically you asked (edited for clarity): I have a question concerning clearance requirement in sub-clause 5.4.2.3.2.2, Determining AC mains transient voltages: “In general, clearances in equipment intended to be connected to the AC mains, shall be designed for Overvoltage Category II. Equipment that is likely, when installed, to be subjected to transient voltages that exceed those for its design overvoltage category requires additional transient voltage protection to be provided external to the equipment.” Question: Whether the phrasing “shall be designed for Overvoltage Category II” is always required despite the fact that the sentence begins with the words in general? Is it allowed to use lower mains transient value to reduce the clearance by using external surge protection module in mains supply side? How about internal surge protection?

In response, although it is unclear from your question whether the equipment subjected to the enquiry is equipment installed indoors or outdoors, it is noted that requirements in IEC 62368-1:2018 now consider both indoor and outdoor applications, whereas in IEC 62368-1:2014 it only covered indoor applications (with outdoor applications covered by IEC 60950-22).The outdoor locations requirements from IEC 60950-22 have been incorporated into IEC 62368-1:2018, including those that impact requirements for surge protection devices and consideration of transient voltages.

Sub-clause 5.4.2.3.2.2 in IEC 62368-1:2018 currently is clear that installed equipment likely to be subjected to transient voltages that exceed those for its design overvoltage category (e.g., OV Cat II) requires additional transient voltage protection to be provided “external” to the equipment, in which case, the installation instructions shall state the need for such external protection. Currently, in 5.4.2.3.2.2 of IEC 62368-1:2018 it does not mention use of such protection inside the equipment.

However, also keep in mind, subclause 5.4.2.3.2.1 states, transient voltages can be determined based on their origin, or can be measured in accordance with 5.4.2.3.2.5. If additional surge suppression to address reduced overvoltage category was provided inside the equipment, it is likely that measurement of actual transient voltages per 5.4.2.3.2.5 would be expected / required since the type of surge suppression installed externally typically is different than those installed internally. However, 5.4.2.3.2.5 also requires that surge suppressors internal to the equipment in circuits connected to the mains to be disconnected, which likely would invalidate the advantages of placing surge suppression inside the equipment for most applications.

The complete answer to this topic is complex, and there appears to be a specific, detailed construction that needs review/analysis. Therefore, you are encouraged to contact UL Solutions for an in-depth consultation via https://www.ul.com/services/iec-62368-1-testing-certification.

Clause 5 Electrically-caused injury

For classification of electrical energy sources, is a single fault condition required to be performed on a single Y1 type capacitor connected between primary and secondary (and acting as reinforced insulation)?

Unless otherwise noted, the sub-clause references below are to UL IEC 62368-1 Ed. 3 (IEC 62368-1:2018).

In determining ES class per sub-clause 5.2.1, measurement under a single fault condition is required to be considered. The single fault condition is defined in sub-clause 3.3.7.9, with specified details in sub-clause B.4 - faulting a reinforced safeguard is excluded, and capacitors complying with IEC 60384-14 and assessed according to 5.5.2 also are excluded from being faulted.

In your case of reinforced insulation between primary and secondary, and assuming (as the most likely typical example) an AC mains voltage up to 300 V and overvoltage category II, a single Y1 capacitor is allowed to bridge the reinforced insulation per G.11.3 and the associated table G.12. Therefore, the Y1 capacitor is considered a reinforced safeguard and, since it also meets the criteria of the 4th dash in B.4.6, a single fault condition need not be applied to the capacitor.

Clause 5 Electrically-caused injury

For two varistors connected between both sides of Mains (L & N) and Protective Earthing (PE) through the same GDT, is it acceptable that each varistor withstands a voltage based on half of equipment input voltage rating?

More specifically you asked: For a product with input voltage 100-240 Vac submitted for UL CSA IEC 62368-1 evaluation, does Annex G.8.1 allow using two MOVs between L and N with a midpoint connection to PE through a GDT, if each varistor’s Maximum Continuous Voltage (MCOV) rating (e.g., 215 Vac) passes 1.25 times the half of rated voltage ( 240 / 2 * 1.25 = 150 Vac) of equipment, so therefore the sum of the two varistors (e.g., 215 Vac + 215 Vac = 430 Vac) in series has a total MCOV of greater than the minimum required voltage (240 Vac * 1.25 = 300 Vac) per the upper voltage of the Rated Voltage Range of the equipment?

(L-PE is MOVA+GDT; N-PE is MOVB+GDT; and L-N is MOVA+MOVB)

The construction under discussion consists of two varistors connected between Line and Neutral with a GDT connected midpoint between the two varistors and Protective Earthing. When the GDT is activated, this results in a varistor and GDT in series between L and PE (MOVA+GDT) and a varistor and a GDT in series between N and PE (MOVB+GDT), and, when the GDT is not activated, two varistors in series between L and N (MOVA+MOVB).

In response, per sub-clause 5.5.7, where an SPD is used between the Mains and Protective Earthing, it shall consist of a varistor and a GDT connected in series and the varistor shall comply with Clause G.8 in Annex G.  Per G.8.1, the MCOV of a varistor shall be at least 1.25 times the Rated Voltage (or the upper voltage of the Rated Voltage Range) of the equipment.

With above scenario, the MCOV rating of each varistor of the two is required to be at least 1.25 times the upper voltage of the Rated Voltage Range of the equipment. For the example given, the MCOV rating of each varistor should be at least 300 Vac (i.e., calculated by 240 Vac * 1.25). Therefore, a varistor rated 215 Vac (i.e., less than 300 Vac) is deemed not sufficient per the presently published requirements in Annex G.8.1.

(Note, the currently published requirements are based primarily on consideration of the overvoltage implications of the L or N to PE effects and not the L to N effects. Any proposal (with technical rationale) to adjust this would need to be subjected to the IEC committee expert review process and should be proposed to IEC TC108.)

The complete answer to this topic is complex, and there appears to be a specific, detailed construction that needs review/analysis. Therefore, you are encouraged to contact UL Solutions for an in-depth consultation via https://www.ul.com/services/iec-62368-1-testing-certification.

Clause 5 Electrically-caused injury

For the purposes of determining accessible parts, what is the difference between plugs/jacks/connectors (i.e., sub clause V.1.4, requiring the use of a blunt probe) and a terminal (i.e., sub clause V.1.6, requiring the use of a terminal probe)?

When determining the application of a requirement in any of the IEC 62368-1 Annexes, it is always important to remember to locate in the base standard content (clauses 1-10) where the Annex is referenced since Annexes are not intended to stand alone without a reference from the base content of the standard.

As a result of doing this:

• Sub-clauses 5.3.2.1 (Accessibility to electrical energy sources and safeguards - Requirements) and 5.4.10.1 (Safeguards against transient voltages from external circuits - Requirements) directly reference the blunt probe (Figure V.3).
• Sub-clause 5.3.2.4 (Terminals for connecting stripped wire) directly references the terminal probe (Figure V.5).

In summary:

• The blunt probe (Figure V.3) is utilized to identify (or “determine” or “assess”) the accessibility of connector pins at ES2 under normal operating conditions, and the pins of the connector shall not be accessible by this probe.
• The terminal probe (Figure V.5) is utilized to identify (or “determine” or “assess”) the accessibility of internal parts classified as ES2 or ES3 through any openings within 25 mm of terminals for connecting stripped wire.

Clause 5 Electrically-caused injury

Does sub-clause 5.4.5 of UL IEC 62368-1 (Ed. 3) apply to both a device connected to an outdoor antenna and an indoor device with a small integral antenna, like a wireless router? Why does a test voltage of 10kV apply?

More specifically you asked (edited for clarity): For the purposes of testing insulation, sub-clause 5.4.5 in Ed. 3 states that the insulation between mains and antenna terminals, and mains and external circuits providing non-mains supply to equipment having antenna terminals, shall withstand electrostatic discharges at the antenna terminals. Is this requirement applicable to any type of antenna? I do not understand why the accessible terminal is tested 50 times at 10kV while the accessible conductor on a USB or ethernet port or similar component is tested against a different voltage. Is clause 5.4.5 only meant for outdoor antenna or would the tiny antenna on an indoor wireless router also need to be tested if it is supplied by a mains power module? And if so, what are the dangers addressed in the case of small indoor devices with tiny antennas such that regular insulation tests are inadequate to deal with it?

In response, sub-clause 5.4.5 of IEC 62368-1:2018 (Ed. 3) does not apply to equipment connected to every type of antenna. The requirement does not apply to indoor devices with an indoor antenna (e.g., on the wireless router). The test voltage applies between mains and any terminals directly or indirectly connected to an outdoor antenna only. For equipment connected to an outdoor antenna, the specified insulation is required to withstand electrostatic discharges because a high voltage (up to 10kV) caused by electrostatic charge may accumulate over time on the outdoor antenna due to environmental effects, like dust blowing against the outdoor antenna. For a more detailed background of this requirement, please consult sub-clause 5.4.5 in the “Rationale document”, IEC TR 62368-2:2019.

Clause 6 Electrically-caused fire

Does a DC bus bar that can carry 48 V, 6000 A (ES1, PS3) need a fire enclosure?

More specifically, you asked (edited for clarity): If a device has DC bus bars that can carry 48 V and 6000 A (ES1, PS3) and the bus bars (multiple, stacked together) are separated by an insulator having a flammability rating of V-0 at the thickness used, would the bus bars need to be encased in a fire enclosure per IEC 62368-1? The standard doesn't necessarily delve into busbars.

In response, although the bus bars are operating at 48 VDC and are not a risk of electric shock (ES1), they are carrying greater than 100 VA, so they are a risk of fire (PS3) per Clause 6, Electrically-caused fire.

Furthermore, since the available power of the circuit exceeds 4000 W, per sub-clause 6.4.1 the reduce the likelihood of ignition option for safeguarding against fire under single fault conditions is not permitted. Therefore, per sub-clause 6.4.1 the control fire spread option needs to be applied for such safeguarding against fire under single fault conditions, which per sub-clause 6.4.6 requires a fire enclosure to be provided in accordance with sub-clause 6.4.8 (among other considerations specified in the sub-clause). So, for the described construction, yes, a fire enclosure is required per IEC 62368-1 Clause 6.

Additionally, sub-clause 4.9, Likelihood of fire or shock due to entry of conductive objects, has additional consideration for PS3 circuits, including reference to Annex P, Safeguards against conductive objects.

Also noteworthy in the context of bus bars, IEC 62368-1 does not have requirements for safeguarding from a 240 VA energy hazard that was previously located in sub-clause 2.1.1.5 of IEC 60950-1. Please refer to IEC TR 62368-2, Explanatory information related to IEC 62368-1, under Clause 5 for a complete explanation why.

As this forum is not intended to analyze and provide guidance on specific designs, we recommend that you contact UL Solutions and request an in-depth consultation if you have a specific design or construction that you would like to discuss.

Clause 6 Electrically-caused fire

Do the revisions to IEC 62368-1, 4th ed Sub-clause 6.4.8.3.4 (Bottom openings and bottom opening properties) impact products currently certified to IEC 62368-1 2nd or 3rd edition?

More specifically, you asked (edited for clarity): Per IEC 62368-1, 4th ed, Sub-clause 6.4.8.3.4, will products currently certified to IEC 62368-1 2nd or 3rd edition need to be reevaluated or are the revisions just clarifications to existing requirements?

In response, the revisions to Sub-clause 6.4.8.3.4 are both an editorial clarification, and the addition of a bottom opening construction option that may be used as an additional alternative to the previous requirements.

Clarification has been provided in the actual sub-clause that the 2 mm boundary associated with the Figure 42 fire cone must be considered when applying requirements for bottom openings. However, this clarification is expected to be consistent with present practice since this same information was previously included directly in Figure 42.

Additionally, a new provision and modified figure (44) has been added to this subclause. It states, “For professional equipment intended for use in environments where combustible materials are unlikely to be adjacent to the product (for example, data centers and server rooms), extended bottom surfaces may be considered a suitable fire enclosure as illustrated in Figure 44 if the bottom surface complies with 6.4.8.3.4.” For constructions that will be covered by this new provision and modified figure, the overall requirements are considered less onerous than previous (providing manufacturers with another option).

It is noted, there appears to be an error in the modified Figure 44 not illustrating fully the construction covered in the new provision discussed above. It is anticipated that this error will be corrected in a planned Corrigenda to IEC 62368-1:2023.

As this forum is not intended to analyze and provide guidance on specific designs, we recommend that you contact UL Solutions and request an in-depth consultation if you have a specific design or construction that you would like to discuss.

Clause 6 Electrically-caused fire

What are the requirements for fire enclosure openings when a product can be positioned in multiple orientations?

More specifically, you asked (edited for clarity): We would like to ask about the requirements for ventilation openings for the heat transfer and protection against the fire risk. If we want to design our product to be in both vertical and horizontal orientations, what requirements should we follow?

In response, the UL 62368-1, Edition 3 requirements for fire enclosure openings are specified in sub-clause 6.4.8.3 and equipment orientation is specified in sub-clauses 4.1.4 and 4.1.6.

Fire enclosure opening requirements are dependent upon their proximity to a Potential Ignition Source (PIS). Per sub-clauses 4.1.4 and 4.1.6, where it is clear that the orientation of use of equipment is likely to have a significant effect of the application of the requirements, all orientations of use specified in the installation or user instructions are required to be taken into account. However, if the equipment has means for fixing in place by an Ordinary Person, such as screw holes for direct attachment to a mounting surface through the use of mounting brackets, either provided with or readily available on the market, all likely positions of orientation are to be taken into account, including mounting to a non-vertical surface regardless of the installation instructions provided by the manufacturer. These orientations would need to be taken into account when determining whether an enclosure opening is considered a top, bottom or side opening with regards to their proximity to a PIS.

Top opening requirements are specified in sub-clause 6.4.8.3.3, bottom opening requirements are specified in sub-clause 6.4.8.3.4, and side opening requirements are specified in sub-clause 6.4.8.3.6. Please note that side openings also may be considered bottom openings if they are within a 5 degree downward projection from the PIS as noted in Figure 44.

Also, in the latest edition, IEC 62368-1:2023, there has been some refinement of the construction requirements for fire enclosure and fire barrier openings throughout sub-clause 6.4.8.3, so it is recommended that you review the latest changes. Please refer to the UL Solutions’ Certification Impact Analysis: IEC 62368-1:2023 (Edition 4) for additional insight.

As this forum is not intended to analyze and provide guidance on specific designs, we recommend that you contact UL Solutions and request an in-depth consultation if you have a specific design or construction that you would like to discuss.

Clause 6 Electrically-caused fire

How to determine PS classification for a passive loudspeaker with no power source (power amplifier) provided, just a rated maximum power handling capacity?

More specifically you asked (modified for clarity): Regarding Power Source (PS) classification, how are you supposed to perform measurements on equipment that does not contain a defined power circuit and is delivered without one, such as a passive speaker? The speaker may have a rated power handling capacity, but the actual details of the power circuit (amplifier) are unknown and will most probably vary in later use. For a worst-case fault in the load, the maximum delivered power is dependent on the specifications and behavior of the power amp.

In response, to assess a passive loudspeaker that does not have a specific power source, reliance is placed on the information, including recommendations and ratings, provided by the manufacturer.

Although sub-clause F.3.3.2, Equipment without direct connection to mains, of IEC 62368-1 does not require equipment without direct connection to mains to have an electrical rating, it is standard industry practice for passive loudspeakers to have information or a rating related to power handling capacity. For lack of other details, this information can be used to establish a PS level classification for a passive loudspeaker, along with any other relevant information provided by the manufacturer.

For classifying part of an overall system for PS, although imperfect, this approach is relatively consistent with the general information in sub-clause 6.2.2.1 of IEC 62368-1:2018.

However, it should be noted that IEC 62368-1:2023 includes numerous changes related to loudspeaker drivers and loudspeaker driver assemblies that were incorporated, in part, due to some of the challenges classifying loudspeaker drivers and assemblies that your question introduces. In fact, most of the safeguards against risk of electrical fire in Clause 6 of the latest edition have exceptions for loudspeaker drivers and loudspeaker driver assemblies due to their unique design requirements and the lack of adverse field incident data, which also is consistent with past practice under IEC 60065. Therefore, PS classification of loudspeaker drivers and assemblies is less important under IEC 62368-1:2023.

As this forum is not intended to analyze and provide guidance on specific designs, we recommend that you contact UL Solutions and request an in-depth consultation if you have a specific design or construction you would like to discuss.

Clause 6 Electrically-caused fire

Can a loudspeaker driver in PS3 circuit be exempt from fire enclosure requirements if applying for UL 62368-1?

More specifically you asked (edited for clarity): I am currently developing a bass reflex subwoofer speaker which is driven by a PS3 amplifier output. The subwoofer shall comply with UL 62368-1. However, because of that, one could think that the driver itself needs to be housed within a fire enclosure against the spread of fire. This would limit the maximum hole size on the front grille to a maximum of 3mm if the speaker is oriented top down and the grille holes become bottom openings. Is there an exception of this rule for loudspeakers?

In response, a fire enclosure is the primary safeguard for protection against fire when relying on the “control fire spread” method covered in sub-clauses 6.4.4, 6.4.5 and 6.4.6 of UL 62368-1:2019. However, there is another method of investigation allowed for by sub-clause 6.4.1 of UL 62368-1:2019, which is the “reduce the likelihood of ignition” method, covered by sub-clauses 6.4.2 and 6.4.3. In the application of the “reduce the likelihood of ignition” method, a fire enclosure, including opening size limitations for different orientations, is not required. However, via performance testing, the equipment needs to demonstrate that no internal parts have sustained flaming. According to Annex B.4.6, loudspeakers shall be short-circuited or disconnected, whichever is more unfavorable. Also noteworthy, per sub-clause 6.4.1, this method only is permitted for circuits in which the available steady state power does not exceed 4,000 W, such as most applications of pluggable equipment type A.

Note too, UL 62368-1 Ed.4 remains under development and likely will be published in the second half of 2024. It will be based on IEC 62368-1:2023, for which we would like to provide some additional information for your reference. There are many changes related to loudspeaker drivers and assemblies in IEC 62368-1:2023, such as in sub-clauses 3.3.6.11, 6.3.1, 6.4.5.2, 6.4.6, and 6.4.7.1. In fact, it states in sub-clause 6.4.6 that a fire enclosure is not necessary for loudspeaker drivers/assemblies. This change in Edition 4 provides some design relief for manufacturers of loudspeaker drivers and assemblies without compromising safety due to the unique design requirements for such loudspeaker drivers and assemblies and lack of any field incident data, which also is consistent with past practice under IEC 60065.

As this forum is not intended to analyze and provide guidance on specific designs, we recommend that you contact UL Solutions and request an engineering engagement if you have a specific design or construction that you would like to discuss.

Clause 6 Electrically-caused fire

Can the marking on a wire be used as evidence of compliance with VW-1 rating requirements?

More specifically, you asked: When demonstrating compliance with IEC 62368 wire flammability by way of the VW-1 equivalence concession, if a manufacturer has a file listing for AWM Style No. 20276 (which conforms to UL 758, the Standard for Appliance Wiring Material, which itself states a number of flammability tests that can be applied), where is the evidence of which flammability test was used? Is it sufficient to rely on the product marking? If a cable is marked “[File Number] [UL logo] AWM Style 20276 80C 30V VW-1,” is that sufficient to state that it meets VW-1 on the basis that UL Solutions controls such markings, or is there a further document or certificate that should be provided to show which flammability test was performed?

In response, we confirm that a VW-1 rating is acceptable based on a National Difference for USA/Canada (in Annex DVF (6.5.1)) with its reference to UL 2556. A reference to UL 2556 VW-1 is also in Subclause 6.5.1 of IEC 62368-1, Ed. 3, which provides this option for wider use under IEC 62368-1, although the acceptance is at the discretion o a National Certification Body(NCB).

For wires recognized by UL Solutions under the AVLV2 category, the markings, including identification, ratings and the UL Mark, provided on a spool (tag, reel or smallest unit container) are considered the evidence of formal compliance and UL Component Recognition. Please see the AVLV2 Guide Information in the UL Product iQ® database for more details. The marking provided on the wire itself is for reference only and, alone, generally is not considered direct evidence of UL Component Recognition during end-product UL Solutions Follow-Up Services.

Please note that there may be a benefit for your wiring and wiring harness suppliers to get covered under one of our traceability programs, like the UL Wiring Harness Program. Then you could trace the certification and ratings of your components to the original certification markings associated with the spool, etc. More than 3,000 wiring harness suppliers are currently certified under the wiring harness program, so some of your suppliers may already be covered.

Clause 6 Electrically-caused fire

What are the requirements for internal and external wiring according to IEC 62368-1 Ed 3 and UL 62368-1 3ed.?

More specifically you asked (edited for clarity): I am seeking product certification to IEC 62368 and have come up against the wire flammability issue – I note a previous answer regarding equivalence with VW-1, but what about superior standards – such as CL2? Is there a means by which CL2 being superior (i.e., NEC allows substitution) to VW-1 that allows me to demonstrate compliance with 62368?

In response, as you inferred the note under sub-clause 6.5, Internal and external wiring, in the IEC 62368-1 Ed. 3, as well in the UL 62368-1 Ed. 3, accepts UL 2556 rated VW-1 wires to demonstrate compliance with 6.5.1 as an alternative method, which we confirm.

In addition, for external wiring according to the US / CAN Deviations under 4.1.17DV.1, External interconnecting cable and wiring, it is to be investigated to the requirements of sub-cl. 6.5 and either 4.1.17DV.1.2 or 4.1.17DV.1.3, depending on the cable length.

External interconnecting cable and wiring 3.05m or less may be investigated as part of the equipment (system) to the requirements of this standard, depending on the PS circuits involved:

• external interconnecting cable and wiring connected to PS2 or PS3 circuits, the flammability requirement of 6.5 applies;
• there are no flammability requirements for external interconnecting cable and wiring in PS1 circuits.

Other external interconnecting cable and wiring exceeding 3.05m in length are required to comply with 4.1.17DV.1.3, including the references to the Canadian Electrical Code, Part I, CSA C22.1, and the National Electrical Code, NFPA 70 under Annex DVA (Annex Q), where CL2 Listed Cables are allowed to be used in Class 2 and LPS circuits.

Such CL2 cables are UL Listed as Power Limited Circuit Cable (QPTZ), information for which can be found in UL Product iQ®.

Please note, CL2 cables are subjected to a Vertical-Tray Flame Test in UL 1685, Vertical-Tray Fire-Propagation and Smoke-Release Test for Electrical and Optical-Fiber Cables, which is a more onerous test than VW-1. Therefore, if a manufacturer wanted to also substitute Listed CL2 cables for internal wiring or external cabling not exceeding 3.05m in length, that would be considered acceptable too, as long as the circuit were Class 2 or LPS. However, most manufacturers choose not to do so due to cost considerations.

The complete answer to this topic is complex, and there appears to be a specific, detailed construction that needs review/analysis. Therefore, you are encouraged to contact UL Solutions for an in-depth consultation via https://www.ul.com/services/iec-62368-1-testing-certification. 

Clause 6 Electrically-caused fire

How does IEC 62368-1 handle “Small Parts” in the context of flammability requirements?

As we know, in the context of risk of fire, the use of the term “small parts” often was the source of some confusion in IEC 60950-1. 

For example, in 4.7.3.4 of 60950-1, the following parts did not have to comply with the V-2 requirement for combustible parts inside a Fire Enclosure: “electronic components, such as integrated circuit packages, optocoupler packages, capacitors and other small parts that are mounted on V-1 Class Material.”

Often a point of discussion under 60950-1 was – what exactly is considered a small part?

The answer typically was, there is subjectivity and engineering judgment involved, including the size of the part in relation to its micro-environment and its proximity to other combustible parts. Ultimately, engineering judgment was involved.

So, in the context of IEC 62368-1, does anything change with the principle/requirement and use of this terminology?

The answer is, yes.

In IEC 62368-1, the terminology “small parts” is not used. 

In its place are two more precise descriptions of parts that are exempt from flammability requirements for similar applications:

• parts with a size of less than 1,750 mm3 (volume);
• combustible material less than 4 g (mass).

In the IEC TR 62368-2 “Rationale” document, it states the origin of these specifications are the practical use of them under IEC 60065 for AV equipment safety. So, on one hand, the subjective nature of the terminology in IEC 60950-1 no longer will be such an issue.

On the other hand, the subjective nature of the terminology in IEC 60950-1 replaced with more precise parameters in IEC 62368-1 might tend to limit some of the “engineering judgment” that was allowed for under 60950-1.

Clause 6 Electrically-caused fire

For IEC 62368-1, can I conduct single fault testing in lieu of providing a fire enclosure like was allowed for in IEC 60950-1 for some constructions?

The short answer is, no – in most cases not exclusively.

Here is the longer answer.

Clause 6 of IEC 62368-1 requires safeguards to be in place against fire under normal, abnormal and single fault conditions.

Per Clause 6, typically, one safeguard (or safeguard system) is provided to protect under normal and abnormal operating conditions, and another safeguard (or safeguard system) is provided to protect under single fault conditions.

For normal and abnormal operating conditions, the typical basic safeguard consists of limiting temperatures of materials within the equipment to 90% or less of the spontaneous ignition temperature limit of the material.

However, for single fault conditions, manufacturers have the choice of two paths: (a) Reduce Likelihood of Ignition, or (b) Control of Fire Spread.

(In larger systems it is possible to use both paths for different parts of the system.)

In 60950-1, the Reduce the Likelihood of Ignition path is parallel to the “simulated fault test” option (its Method 2); the Control of Fire Spread path is parallel to the “fire enclosure” option (Method 1).

However, in 62368-1 there is one area that is causing some confusion (compared to 60950-1), mainly the application of the Reduce the Likelihood of Ignition path.

Based on 60950-1 experience, it is easy to assume a performance test program exclusively of single fault testing can be used to satisfy this Reduce the Likelihood of Ignition path (as was allowed for to a certain degree in 60950-1). While single fault testing certainly is the primary performance aspect of this 62368-1 safeguard, in PS2 and PS3 circuits there remains (per 6.4.3.2 Ed 2/6.4.3.1 Ed 3) a minimum separation requirement (distance or barrier) from both arcing & resistive PIS (potential ignition sources), which in some cases could require a barrier, flame testing per Annex S, or preselected V-1 or V-0 material, in addition to single fault testing.

Sub-clause 6.4.3.2 (6.4.3.1/Ed 3) of IEC TR 62368-2 (rationale document) provides the associated rationale, primarily that prescribed use of a fire cone (from 60065 experience) is more reliable than single fault testing for predicting risk of fire – single fault testing is not considered by IEC TC108 as wholly representative. Therefore, IEC TC108 included additional material and construction requirements (fuel control area or keep out area) in addition to single fault testing.

It is important to be aware of this difference between 60950-1 and 62368-1 for this performance-based option in lieu of fire enclosure.

Clause 6 Electrically-caused fire

Does Clause 6 of IEC 62368-1 only allow for wiring & cable complying with the flammability requirements in IEC 60332-1-2, IEC 60332-1-3, IEC 60332-2-2, or IEC/TS 60695-11-2?

More specifically you asked: Clause 6 of IEC 62368-1 requires most wiring & cable to comply with the flammability requirements in IEC 60332-1-2, IEC 60332-1-3, IEC 60332-2-2, or IEC/TS 60695-11-2. However, I have difficulty securing wiring from my wire & cable vendors that meet one or more of these standards. Will this be a problem transitioning to IEC 62368-1?

IEC TC108 implemented a solution in Edition 3 (IEC 62368-12018).

For those familiar with Ed. 2 IEC 62368-1, there are several references in Clause 6 (Electrically-cause Fire) to IEC 60332-1-2, IEC 60332-1-3, IEC 60332-2-2, and IEC/TS 60695-11-2. For example, in sub-clause 6.5 (Internal and external wiring), for wiring in PS2 or PS3 circuits the sub-clause states that the insulation on internal or external wiring shall pass the test methods in one of these IEC standards. 

However, as you noted, manufacturers have had a challenge sourcing insulated wire that complies with one of these IEC standards. Although UL Solutions for several years has offered wire & cable test/certification to these IEC standards, the number of certifications available still have not met the industry need.  

IEC TC108 modified these flammability requirements in Ed. 3 of IEC 62368-1. Supplementing references to the IEC flammability test standards is a modifier, “or equivalent,” in addition to an informative note that states “Wire complying with UL 2556 VW-1 is considered to comply with these requirements.”  

The UL 2556 VW-1 test method essentially is equivalent to (harmonized with) the test method in IEC/TS 60695-11-2 so there was TC108 support for formally recognizing readily available VW-1 rated wire as another option. This modification makes it much easier for manufacturers to source wire & cable compatible with 62368-1’s Clause 6 requirements. 

This change in IEC 62368-1 is one of numerous examples of IEC TC108 introducing practical, yet sound considerations on an ongoing basis with new editions.

Clause 6 Electrically-caused fire

What are the rules for opening size, number of openings and minimum spacings between the openings per 6.4.8.3.3 and 6.4.8.3.4 of a fire enclosure? When is testing required? Does the standard allow for a mesh or grid to be provided to cover the openings?

(References are to IEC 62368-1:2014 (Ed. 2) except where otherwise noted.)

As stated in 6.4.8.3.3, top/side openings that are within the fire cone of Figure 41 are treated as top openings and shall not exceed 5 mm in any dimension or 1 mm in width regardless of the length. If the openings exceed those dimensions, the standard requires the needle flame test of Clause S.2 which shall be applied as explained in 6.4.8.3.3.

The standard does not rule out other options such as providing a mesh or barrier, the acceptability of which will need to be determined upon review of an actual sample. Additionally, the standard has no requirement specifying the maximum number of top/side openings that may be provided. There are also no requirements regarding the spacings between the openings for top/side opening. However, keep in mind that too many openings may affect the strength of the enclosure. The robustness of an enclosure safeguard will be assessed per subclause 4.4.4, by the mechanical strength tests of Annex T if deemed necessary. An enclosure functioning as an electrical and fire enclosure (safeguard) will need to meet all applicable performance requirements.

The standard defines bottom openings as any openings within the zone as shown in Figure 42 including intersection with side openings as noted in 6.4.8.3.4. In lieu of the flammability tests in Clause S.3, the standard allows several options for compliance with the requirements as explained in 6.4.8.3.4 a) through d).

As stated in 6.4.8.3.4 a), openings that do not exceed 3 mm in any dimension or 1 mm in width regardless of length are considered to comply. As stated in b), openings may go up to 6 mm in any dimension, or 2 mm in width if located under components that are rated minimum V-1, HF-1 or components that pass the needle flame test of IEC 60695-11-5. Alternatively, as explained in c) the standard also allows a metal mesh that does not exceed 2 mm by 2 mm of at least 0.45 mm diameter wire to be provided. One last option which only applies to metal enclosure is explained in 6.4.8.3.4 d) and detailed in table 34. Openings shall be dimensioned and spaced away per that table based on the thickness of the enclosure and shape of opening (circular or other). The standard does not specify any limits on the number of bottom openings if they are adequately spaced away per the table.

Please also note, there are additional requirements for openings in Annex P that are not fire related and can impact size of openings.

However, in IEC 62368-1 Ed. 3 extensive revisions were made to fire enclosure requirements that affect enclosure openings. First, in 6.4.8.3.1, Fire enclosure and fire barrier openings,  see new Figure 40 “ Determination of top, bottom and side openings.  Extensive revision also was made to 6.4.8.3.5, Side openings and side opening properties, which can result in areas of the side enclosure having no restriction for fire considerations. For top openings subjected to performance testing, also note modifications to, Application of needle flame, in Annex S.2, Flammability test for fire enclosure and fire barrier integrity, including new Figure S.1. Also, in 6.4.8.3.4, Bottom openings and bottom opening properties, for openings below the PIS, the principles and requirements now are much closer to IEC 60950-1, including the reintroduction of the 5 degree downward projection principle. Finally, also in 6.4.8.3.4, original options c) and d) have been removed since this type of construction is considered to meet the criteria of the second part of option b).

Clause 6 Electrically-caused fire

How to determine whether a component like a capacitor, inductor, FET or IC is considered a Potential Ignition Source (PIS), and what is an accurate definition of a single fault condition?

More specifically you asked, 1) how to evaluate whether cap, inductor or MOSFET on power rail are PIS or not. 2) What’s the accurate definition of single fault? For a cap, can we set its resistor to several ohms under single fault condition? 3) How to evaluate whether an IC can become PIS under single fault condition?

IEC 62368-1 does not distinguish whether a component is a PIS based on type of component, such as capacitor, inductor or MOSFET. There are two Potential Ignition Source (PIS) types, Arcing PIS and Resistive PIS. Depending on the level of power involved, the specific types of components mentioned above could be a Resistive PIS. Ed. 2 of IEC 62368-1 defines a component as being considered a Resistive PIS if located in a PS2 or PS3 circuit, and either dissipates more than 15 W measured after 30 s under normal operation conditions, or under single fault conditions of other components, either has an available power level over 100 W for 30 s if power limiting components are involved, or for other components has an available power of 15 W after 30 s. However, Ed. 3 refines these conditions for Resistive PIS to only consider “dissipation” of power through the component, no longer considering “available power.”

Also, per its definition in sub-clause 3.3.7.9, a “single fault condition” means that with the condition of equipment under normal operation, a fault is introduced to a single safeguard, component or device. Annex B.4 provides some typical single fault conditions, such as short-circuit, interruption, or disconnection of semiconductors and passive components accordingly. Where single fault is considered in defining a Resistive PIS, Annex B.4 also is applicable. Fault simulation applies to the actual circuit and component construction, and there is no alternative approach via use of other simulated components, such as the utilization of equivalent resistor for a capacitor.

The dissipation through the IC would have to be monitored during single faults of other components. Keep in mind, the manufacturer can always select to declare a Resistive PIS, so then detailed measurements do not need to be made. This is common practice for many manufacturers.

Questions like these are best discussed directly with UL Solutions based on your specific situation, and outside of a public forum like this. Therefore, you are encouraged to contact UL Solutions for an in-depth consultation via https://www.ul.com/services/iec-62368-1-testing-certification.

Clause 6 Electrically-caused fire

For DC powered products with internal PS2 circuits and containing only resistive PIS, does this construction require a Fire Enclosure?

All references are to IEC 62368-1:2018.

In case of the “Reduce the likelihood of ignition” method, including application of 6.4.3, a fire enclosure normally is not required. However, if separation from PIS requirements are not met per the first dash of 6.4.3.1, then a suitably rated fire barrier would be required. Therefore, this method may not be the best method for the type of application you describe. (The first dash paragraph of 6.4.3.1 states, “- an arcing PIS or a resistive PIS shall be separated as specified in 6.4.7 with the accessible outer surface of the equipment considered to be covered with a combustible material.”)

In case of the “Control fire spread” method, for a product only having PS2 circuits inside the product complying with 6.4.5, a PS2 circuit does not require a fire enclosure, regardless of whether PIS also is available. However, note the component requirements in 6.4.5.2, in which one option is adequate separation from a PIS, although it is not the only option.

Please also note that if the DC powered product also has a secondary lithium battery inside, M.4.3, Fire enclosure, of Annex M also is required. Unless the cell is PS1, a fire enclosure, V-1 or better, is required for the cell or combination of cells. The product enclosure also can serve as the fire enclosure required by M.4.3. IEC TC108 also has a formal Interpretation for M.4.3 that PIS considerations and separation from combustible parts need not be considered inside batteries. Therefore, in such batteries, even for PIS in very close proximity to the enclosure, a V-0 material would not be required even when normally required by 6.4.8.4.

Clause 6 Electrically-caused fire

Determination of a Resistive PIS is described differently in Ed. 2 versus Ed. 3 of IEC 62368-1. Are they different test methods? How does one actually measure the power dissipated by a component or any other location?

More specifically you asked (edited for clarity): How to understand the Resistive PIS exactly, because it says “dissipate power more than 15W” in the 62368-1 Ed. 3, while it states “have an available power exceeds 15W” in Ed. 2. My questions: 1) does it mean different test methods per 2nd and 3rd edition? 2) how to measure the dissipation power under normal and single fault conditions? 3) The definition says “location” while it says “any part in PS2 or PS3” in clause 6.2.3.2. Can we regard it as any two points in the PS2 or PS3 circuits, or only consider components like resistor, capacitors, inductors etc.?

In IEC 62368-1:2014 (Ed. 2), sub-clause 6.2.3.2 specifies the criteria to determine a Resistive PIS. Specifically, under a single fault condition the requirement inadvertently focused on the available power from the power source to the part rather than the power dissipated by the part in question. However, this Ed. 2 criteria likely could result in the conclusion that every component in a PS2/PS3 circuit was a Resistive PIS regardless of whether an individual component actually dissipated excessive power that could cause overheating. (The definition of a Resistive PIS in 3.3.9.3 includes the statement “where a component may ignite due to excessive power dissipation.”)

In fact, IEC TC108 HBSDT discussed whether the criteria in 6.2.3.3 of Ed. 2 were appropriate in determining resistive PIS as intended by its definition per 3.3.9.3. IEC TC108 concluded the 6.2.3.2 criteria in Ed 2 was too onerous. Therefore, in the latest Ed. 3 the criteria under single fault conditions have been revised to focus on the power dissipated by a part instead of the available power from the power source, which now is more aligned with the definition of Resistive PIS per 3.3.9.3.

The complete answer to this topic is complex, and there appears to be a specific, detailed construction that needs review/analysis. Therefore, you are encouraged to contact UL Solutions for an in-depth consultation via https://www.ul.com/services/iec-62368-1-testing-certification.

However, in general, power dissipated by a component, such as resistor, will be measured by first measuring current through the component and the voltage across the component while the equipment is in normal operation, followed by, while using the same measuring set-up, initiating any single fault condition that may increase the current or voltage through the same component. Applicable single fault modes are considered based on circuit analysis.

We note the term “location” is used in 3.3.9.3 since a PIS does not necessarily need to be a common component, although typically it is.

Clause 6 Electrically-caused fire

With regards to sub-clause 6.2.2 of IEC 62368-1:2018 (Edition 3), what is the failure criteria of PS1 under abnormal and single fault conditions on load and power source circuits?

In Sub-clause 6.2.2.1, it is specified the electrical power source classification shall be determined by measuring the maximum power under each of the following conditions:

6.2.2.2 – Worst-case fault; and

6.2.2.3 – Worst-case power source fault.

Therefore, PS Class (PS1, PS2, PS3) is determined by the above two measurements.

Worst-case (load) fault (6.2.2.2) represents any fault in the load circuit to draw maximum power from the power source.  In particular, the fault is “simulated” by additional load (as “LVR”) shown in Figure 34.The “LVR” is adjusted to draw maximum power from the power source while it is operated under normal operating condition. Note that single fault of components associated with the load is not actually conducted for Worst-case (load) fault.

However, in Worst-case power source fault (6.2.2.3), single fault testing (of components) is conducted in the power source circuit while the load is normally operated.

The criteria of PS1 as specified in 6.2.2.4, “power source measured according to 6.2.2 does not exceed 15 W measured after 3 seconds,” applies to the measurement results from both Worst-case fault and Worst-case power source fault.

Although the energy source of ES, MS, TS or RS in this standard is classified under Normal, Abnormal and Single fault conditions, PS classification is made by different method. It is classified according to measured maximum power under Worst-case fault (6.2.2.2) and Worst-case power source fault (6.2.2.3).

Clause 6 Electrically-caused fire

What is the requirement for a pluggable connector located in PS3 circuits and used to connect/disconnect with/without load?

More specifically you asked (edited for clarity): We have an IT device (UL listed) according 62368-1 with a power/data port (max. 30V, max. 8A) to supply external connected devices. The port in the device is classified as PS3. The requirements for the connector of the port for fire protection is min. V-1 , because the port is part of the fire protecting housing of the device. Now my questions: If I use a cable >3.05m I need a UL listed cable, but which requirements are applicable to a pluggable connector inline the cable? If the connector is used to connect/disconnect with/without load, which requirements do the connector (plug/socket) need?

When the pluggable connector on external cable (length > 3.05m) is located in PS3 circuit, UL IEC 62368-1 (Ed. 2 or 3), sub clause 6.4.6, second dash still applies for flammability requirements. Generally, material with V-1 flammability rating will meet this requirement, but there are other options in this second dash, such as to comply with flammability testing per S.1, or use of a connector that meets an appropriate IEC component standard. If the connector also can be disconnected under load, the IEC connector standard should consider this condition, and per Annex DVG (G.4.3), if UL 1977 is used its current interruption requirements apply. Generally using a connector certified to UL 1977 suitable for current interruption will meet this requirement.

The complete answer to this topic is complex, and there appears to be a specific, detailed construction that needs review/analysis. Therefore, you are encouraged to contact UL Solutions for an in-depth consultation via https://www.ul.com/services/iec-62368-1-testing-certification.

Clause 6 Electrically-caused fire

May the 3.5mm audio output jacks of laptop computers and phones be “declared” as PS1?

More specifically you asked (edited for clarity): With regards to 3.5mm audio output jacks from a laptop or phone, some of these ports provide a bias voltage and are considered a power source. Bias voltage is in the area of 1.5-1.75 VDC. Could these ports / sources be “declared” PS1 for headphone, headset devices that plug into them?

In response, PS classifications per clause 6 are based on available energy to a circuit, measured in Watts, and are independent of the voltage, i.e., theoretically a 1.5-1.75 VDC circuit could be PS2 if greater than 15 W is available. Technically, Clause 6 requires measurement of the output from any port for connection of additional equipment in both Normal and Single Fault conditions to determine the PS level, and this requirement is provided without exception in either IEC 62368-1:2014 or IEC 62368-1:2018. Circuit analysis and engineering judgment may be able to provide enough evidence that PS1 is maintained. However, this can only be done on a case-by-case basis, i.e., all 3.5mm audio output jacks cannot be declared PS1.

The complete answer to this topic is complex, and there appears to be a specific, detailed construction that needs review/analysis. Therefore, you are encouraged to contact UL Solutions for an in-depth consultation via https://www.ul.com/services/iec-62368-1-testing-certification.

Clause 6 Electrically-caused fire

Does every step-down switch mode power supply need to be subjected to Energy Source Classification?

More specifically you asked: If the product has one or more on-board step-down switch-mode power supplies, should these power supplies be classed for Energy Sources? E.g., 5V input to 3V or 1V output.

The complete answer to this topic is complex, and there appears to be a specific, detailed construction that needs review/analysis. Therefore, you are encouraged to contact UL Solutions for an in-depth consultation via https://www.ul.com/services/iec-62368-1-testing-certification.

However below are a few key facts to consider:

Your question is related to the basic principle of IEC 62368-1 and its Hazard Based Safety Engineering approach based on three-block model of safety: energy source class – safeguard – person (or combustible material).

Identification and classification of Energy Sources is the first step to evaluate safeguards required in product. Therefore, all energy sources need to be classified in the product, either based on declaration (e.g., PS3) or evaluation and / or test of the product connect to a representative supply.

When DC-DC converters are involved, the evaluation and classification is not limited to the voltage levels of the circuit supplying the converter; the working voltages and frequency generated within the converter and supplied by the converter also need to be considered. For example, when circuits are intended to be ES1 due to some accessibility requirements in the final application, the entire system and its circuits must be analyzed by construction review and, when required, by measurement and tests such as Working Voltage Measurement and Single Fault Condition (SFC), to demonstrate that the ES1 circuits are not compromised by higher ES2 or ES3 voltages generated within the converter. Investigation and test may show that additional Safeguards are required.

With reference to clause 4.2.3 and 4.2.4, the standard allows manufactures to declare higher class than there is in the product. (For example, if an energy source class 3 is declared by the manufacturer, there is no need to conduct any measurements.)

Also, related to power supplies:

Electrical Energy Source is based on voltage and/or touch current – it is worth noting that switch-mode voltages may be generated that exceed the ES1 limit even if the input to the supply is ES1. Therefore, more detailed evaluation and tests may be needed even for DC-DC converters. However, for most converters, such as provided in the example (5V input to 3.3V or 1 Vdc output), typical switching voltages are not expected to exceed ES1 limits under normal, anormal and single fault condition.

Also, it also is worth noting, per Clause 6, Power Energy Source classification is irrelevant of voltages and depends on available power. Additionally, components may need classification as Potential Ignition Sources.

Clause 6 Electrically-caused fire

Should the cumulative effect of small parts be considered for the exemptions in sub-clause 6.3.1 of IEC 62368-1?

More specifically you asked (edited for clarity): How is the exemption in 6.3.1 of IEC 62368-1 (2014) applied? For “parts having a size less than 1750mm3”, is each part compared to the limit, or are all identical parts added together and the result compared to the limit?  In my case, I have 16 dust caps on F connectors. Each cap measures 910mm3.

In response, it should be noted that the requirements in sub-clause 6.3.1 constitute Basic Safeguards against risk of fire hazard. The purpose of the Basic Safeguard is to mitigate a risk of self-ignition, primarily by limiting temperatures to not greater than 90 % of their spontaneous ignition temperature limit, or use of HB rated materials if the parts are located external to the Fire Enclosure. Two of the exceptions to the main requirement in 6.3.1 cover small components if the parts have a size less than 1750 mm3, or the parts have a mass of combustible material of less than 4 g. IEC 62368-1 does not provide details about cumulative effect restrictions; therefore general principles need to be considered.

The requirements in sub-clause 6.3, including exceptions, rely on the Fire Triangle concept as one of its Hazard Based Safety Engineering principles, which for fire requires 3 key elements: oxygen, heat and fuel. Reducing the amount of combustible materials is acceptable method of preventing fire ignition and spread. In order to consider combustible material as negligible fuel, the overall construction of the product needs to be considered, including the size, count, location, orientation and separation of components. The IEC TC108 Hazard Based Standard Development Team (HBSDT) took these considerations into account when developing 6.3.1.

Regarding the example in your question, since dust cups are individual parts, typically with separation between other similar parts, dust cups on F connectors in typical constructions may be considered as separate components when applying the exceptions in 6.3.1, not requiring a cumulative effect.

The complete answer to this topic is complex, and there appears to be a specific, detailed construction that needs review/analysis. Therefore, you are encouraged to contact UL Solutions for an in-depth consultation via https://www.ul.com/services/iec-62368-1-testing-certification.

Clause 6 Electrically-caused fire

If an external power supply output to a product is power limited in accordance with IEC 62368-1, could the product’s polymeric enclosure be flame rated HB?

Power-limited is an undefined term in IEC 62368-1, although what probably is meant is that the power supply supplying the product has an output limit associated with PS2 (< 100 W), or complies with the Limited Power Source (LPS) criteria, which allows for varying levels of power (not exceeding 100 VA) based on specific voltage, type of overcurrent protection, etc. Although circuits / devices supplied by PS2 or LPS do not require a fire enclosure, combustible parts, including casings, associated with the device / product in most cases are required to be separated from Potential Ignition Sources (PIS) by the 13 mm / 50 mm fire cone (Figs 37 & 38). Combustible parts that are not, may need to be V-1 or V-0 material (or equivalent testing per Annex S), depending on the actual separation distance. If the proper PIS separation distances are maintained, an HB rated casing may be fine. If not, a casing material with a V-1 or V-0 rating typically would be required.  Both Arcing PIS and Resistive PIS are defined in the Standard, but the steady state 15 W limit (after 30 s) associated with Resistive PIS typically has the most impact.

Clause 6 Electrically-caused fire

Can the marking on a wire be used as evidence of compliance with VW-1 rating requirements?

More specifically you asked (edited for clarity): When demonstrating compliance with 62368-1 wire flammability by way of the VW-1 equivalence concession, if a manufacturer has a file listing for AWM Style 20276 (which conforms to UL 758, which itself states a number of flammability tests can be applied), where is the evidence of “which” flammability test was used? Is it sufficient to rely upon the product marking? If a cable is marked “[File Number] [UL logo] AWM Style 20276 80C 30V VW-1” is that sufficient to state that it meets VW-1 (on the basis that UL controls such marking?) Or is there a further document or certificate that should be provided to show which flammability test was performed?

In response, we confirm that a VW-1 rating is acceptable based on a National Difference for USA / Canada (in Annex DVF (6.5.1)) with its reference to UL 2556. A reference to UL 2556 VW-1 also is in sub-cl. 6.5.1 of IEC 62368-1 Ed 3, which provides this option for wider use under IEC 62368-1, although the acceptance is at the discretion of a Recognizing NCB.

For wires recognized by UL Solutions under AVLV2 category, the markings, including identification, ratings and UL Solutions Mark, provided on a spool (tag, reel or smallest unit container) are considered the evidence of formal compliance and UL Solutions Recognition. (Please see the AVLV2 Guide Information under UL Product iQ for more details – https://iq.ulprospector.com/en/profile?e=206308.) The marking provided on the wire itself is for reference only and, alone, generally is not considered as direct evidence of UL Solutions Recognition during end-product Follow-up Service.

Please note that there may be a benefit for your suppliers of wiring and wiring harnesses to get covered under one of UL Solutions traceability programs, like the UL Solutions Wiring Harness Program – https://www.ul.com/services/wiring-harness-traceability-program. Then you would be able to trace the certification and ratings of your components to the original certification markings associated with the spool, etc. (Over 3000 wiring harness suppliers currently are certified under the wiring harness program, so some of your suppliers may already be covered – https://iq.ulprospector.com/en/profile?e=212703.)

Clause 6 Electrically-caused fire

For a constant current circuit, since the output current already is determined, how is the limited energy circuit determined?

More specifically you asked (edited for clarity): In IEC 62368-1, it is understood how to calculate the maximum current to determine the limited energy circuit for a constant voltage circuit (tables 17 and 18). However, in the case of a constant current circuit, since the output current already is determined, how to determine the limited energy circuit?

In response, the reference to Tables 17 and 18 in your inquiry is not clear. We assume you meant Figures 17 and 18 of IEC 62368-1:2018 since Tables 17 and 18 are for determining the required clearances/creepage distances. We also do not quite understand what you meant by constant voltage although we suspect you probably meant DC voltage. It is also not clear if you were referring to an energy source in the context of electrical energy source (ES1, ES2, ES3) as defined in Clause 5, or in the context of power energy source (PS1, PS2, PS3) as defined in Clause 6. Please note, there is no definition for limited energy in the standard. Therefore, we can only provide a very limited response based on those assumptions.

For the ES levels, per Clause 5, the standard allows either measuring the voltage or the current as shown in Table 4, which shows the value in rms, DC and peak.

For the PS levels, the test methods are in Clause 6 using the circuit setups in Figures 34 and 35. This is used to determine the maximum output power under power measurement for worst-case fault and for worst-case power source fault.

Given the unknowns in your inquiry, and there appears to be a specific, detailed construction that needs review/analysis, you are encouraged to contact UL Solutions for an in-depth consultation via https://www.ul.com/services/iec-62368-1-testing-certification.

Clause 6 Electrically-caused fire

Which general ULSE standards cover VW-1 flammability of wiring. For example, if my wiring material is approved according to UL 1015, can I say that the material is approved also UL 2556 VW-1? Does UL 1015 cover UL 2556 VW-1?

In response, the type of wiring you seem to be asking about is identified as “Appliance Wiring Material” or AWM, which is investigated to UL 758, Appliance Wiring Material. This type of wiring is certified by UL Solutions under our “Appliance Wiring Material” certification category, AVLV2.

We suggest that you register (free) to UL Product iQ® and look up the public Guide Information for AVLV2 – some of the answers to your questions can be answered in the AVLV2 Guide Information – https://iq.ulprospector.com/en/profile?e=206308.

UL 1015 is not a ULSE standard, but it is a AWM Style Number under AVLV2 – Style 1015 sometimes is informally referred to as PVC insulated hook-up wire – https://iq.ul.com/awm/stylepage.aspx?style=1015.

Please note that UL 758 references UL 2556, Standard for Wire and Cable Test Methods, for many of its test requirements, as UL 2556 is a horizontal / reference standard referenced by many UL wire and cable standards. UL 758 also references UL 1581, Reference Standard for Electrical Wires, Cables, and Flexible Cords, for some of its requirements.  In fact, UL 758 references UL 1581 for the test method for conducting the VW-1 (vertical specimen) flame test.

Per the AVLV2 Guide Information, the VW-1 marking is only provided for AWM that complies with the VW-1 requirements – the primary method to identify whether an AWM complies with the VW-1 requirements is for the VW-1 marking to be surface marked on the AWM. Usually, the AWM manufacturer must request VW-1 testing on AWM for the VW-1 testing to be conducted – if the wire passes the VW-1 testing, then “VW-1” can be marked on the AWM.

Note too, under AVLV2 a manufacturer also may request testing to IEC TS 60695-11-21, Fire Hazard Testing – Part 11-21: Test Flames – 500 W Vertical Flame Test Method for Tubular Polymeric Materials, which also is referenced in Clause 6 of IEC 62368-1.

Clause 6 Electrically-caused fire

For China the NOTE allowing wire to comply with UL 2556 VW-1 was removed from sub-clause 6.5.1 by a National Difference from IEC 62368-1 in GB4943.1-2022 (China National Standard). Does this mean VW-1 rated wiring is not accepted in China?

More specifically you asked: China has now published GB4943.1 2022. However, the National Differences exclude wiring tested to UL 2556 and only wire flammability tested to IEC 60332-1 and IEC 60332-2 are acceptable. Given that UL 758 includes the relevant flame tests, will this standard be accepted in China?

In response, the China national difference from IEC 62368-1:2018 in sub-clause 6.5.1 states: “Delete the text of the Note “Wire complying with UL 2556 VW-1 is considered to comply with these requirements.”

In application, it has been determined that this means if a manufacturer of an end product applies for a CCC mark directly, the certification body in China will not accept the internal wiring and external wiring complying with VW-1 flame testing per UL 2556 (Wiring and Cable Test Methods) since the Certification Body considers UL 2556 a regional standard, not an international standard. (Note, UL 2556 is referenced in UL758 (Appliance Wiring Material) for VW-1 test methods.)

However, if a manufacturer applies an end product for a CCC mark via the IECEE CB scheme, and the CB Report states that the internal (or external) wiring complies with UL 2556 (or UL 758) with VW-1 rating, the certification body in China may accept it since UL 2556 is referred to in IEC 62368-1:2018.

Clause 8 Mechanically-caused injury

If our server comes with slide-rails in the box, but can be fitted to any rack, do I have to perform slide-rail mounted equipment testing?

Yes, if the server is provided with slide rails as a possible mounting means, regardless of whether the slide rails are attached at the manufacturing facility, or they are provided in the box for shipment, IEC 62368-1, Sub-Clause 8.11 testing of the mounting rails for slide-rail mounted equipment (SRME) is applicable, unless the product is an MS1 energy source as defined in Table 35 of IEC 62368-1. The Mounting means for rack mounted equipment testing is intended to evaluate the suitability of the mounting hardware, regardless of what rack it is installed in. If a rack is not part of the supplied system, then testing of the SRME with slide-rails is conducted on a representative rack/system.

Clause 8 Mechanically-caused injury

What is the intent of 8.7 of UL 62368-1 for equipment mounted to a wall, ceiling or other structures? Does it cover the mounting means and equipment only, or does it include the equipment, mounting means and mounting to the structure?

More specifically you asked: Sub-clause 8.7 of UL IEC 62368-1 covers test requirements for equipment mounted to a wall, ceiling or other structures. However, it only seems to cover the criteria of the mounting means to the equipment and not the robustness of the equipment to the structure. If the structure is not included into the testing, how are we to ensure that the equipment and mounting means does not cause a hazardous condition to persons after the equipment is fixed to the wall, ceiling, or other structure?

The intent of IEC TC108 in sub-clause 8.7 of IEC 62368-1 was to focus on the integrity of the mounting means connected to the equipment, and not the complete system of equipment/mounting means/structure. The rationale for this is that there are numerous combinations of equipment/mounting means/structures, including the full hardware needed to mount to a variety of structures. Therefore, there is limited ability to attempt to address all combinations in an AV/ICT equipment product safety standard. However, as part of certification AV/ICT equipment with mounting means, some NCBs, like UL Solutions, continue to test representative systems, i.e., equipment/mounting means/representative structure(s), per the supplied installation instructions with the equipment/mount, which then adds additional value to the investigation/certification of the AV/ICT equipment with the mounting means.

Please note, for generic mounting means to accommodate a variety of AV/ICT equipment (such as via a standardized VESA mount design with standardized TV hole placement, etc.), we also have a dedicated standard, UL 2442, Wall- and Ceiling-Mounts and Accessories, and category, IYNW, Wall and Ceiling Mounts and Accessories, which currently includes over 100 Listees having certifications, including most of the major mount manufacturers. These mounts are subjected to representative system testing, including rated loads, recommended structures, etc.

Clause 8 Mechanically-caused injury

For IEC 62368-1:2018 (3rd Ed.), sub-clause 8.6.5, why was the horizontal force test value increased to 20% of the equipment weight, or max 250N, from IEC 62368-1:2014’s (Ed. 2) values of 13% and 100N, respectively?

This horizontal force test applies to constructions with controls or a display and is intended to simulate the force of a child who might climb onto the equipment and engage front-mounted user controls or the moving images on the display. The original horizontal test force applied was 13% of the equipment mass or 100 N, whichever was less, applied to both MS2 and MS3 constructions and was developed to address many field incidents of CRT TVs / monitors in the late 20th century; the details of which are noted in 8.6.5 of “the rationale document”, IEC TR 62368-2. However, more recently, flat panel display TVs / monitors have higher inherent instability in their design, especially if a child were to lean on the edges or controls, and such flat panel display products also are increasing in size/weight. Therefore, IEC TC108 revisited the 8.6.5 requirements and in IEC 62368-1:2018 the force was increased to either 20% of equipment mass or 250 N, whichever is less, to anticipate better today’s larger flat display units considered MS3 (but MS3 only). Please note, for applicable products considered MS2, in IEC 62368-1:2018, the Horizontal Force Stability (8.6.5) requirement has been replaced by Static Stability (8.6.2.2). Also, for applicable products considered MS3, the external horizontal force test remains only one option in 8.6.5, with two variations of the 15-degree tilt test available as alternate performance options.

Clause 9 Thermal burn injury

What is the impact on products of touch temperature limits in 62368-1 as compared to touch temperature limits in 60950-1 and 60065 standards?

Touch temperature requirements in IEC 62368-1 have changed in some respects from those in IEC 60950-1 and IEC 60065. The extent of the impact depends on the type of the product and other considerations as noted below. Therefore, it is impossible to attempt to summarize how they would directly impact a manufacturer's product line without a detailed review of the specific products involved. The following are some highlights of the changes and other things to consider.

First and foremost, the touch temperature limits now are based on measurements in a room ambient of 25 Deg C. Therefore, in most cases the temperature limits are lower. However, a manufacturer’s specified ambient (Tma) that is declared by the manufacturer is no longer factored into touch temperature measurements, although it remains factored into other temperature related measurements, like insulation temperature. This change is the key difference.

The standard takes into consideration the anticipated duration of contact with accessible parts.

The standard has expanded the requirements to take into consideration touch temperature limits for ordinary, instructed and skilled persons and prescribes safeguards for each.

The standard also requires touch temperatures be measured under normal, abnormal operating or single fault conditions and has limits for those conditions.

As in IEC 60950-1 and IEC 60065, IEC 62368-1 has touch temperature limits assigned to different materials. However, the limits have changed and are now more aligned with IEC Guide 117, Temperatures of touchable hot surfaces. In fact, most of the changes related to touch temperatures were made to closely align with IEC Guide 117.

In view of the above, some equipment or products designed to comply with IEC60950-1 or IEC60065 will comply with the new requirements. Some may not. For new products, compliance will be determined by testing. For existing certifications under IEC 60950-1 or IEC 60065, compliance will be determined by testing, or in some cases, review of the existing test reports depending on the complexity of the construction.

Clause 9 Thermal burn injury

Clause 9's Table 38 for Touch Temperature Limits states the limits are based on a 25 deg C ambient. How are the Tmax limits in Table 38 adjusted for different ambient temperatures?

More specifically you asked: Clause 9's Table 38 for Touch Temperature Limits states the limits are based on a 25 deg C ambient and to adjust for different ambient temperatures if not 25 deg C.  What if our product has a max. ambient temperature (Tma) rating of 40 deg C? How are the Tmax limits in Table 38 adjusted?  Do we simply add 15 deg. C to the stated limit in Table 38?

There is a fundamental misunderstanding of Clause 9 (Thermal Burn Injury) and Table 38 in the question.  The intent of 9.2.5, and additional explanation in IEC TR 62368-2, is to convey that the measurements per Clause 9 are made at 25 C ambient (with allowance for test environment), but they do NOT consider Tma, or the manufacturer's specified ambient.  This is different than 60950-1, and thus also supports why the limits in Table 38 are lower. However, the key rationale for why 25 C based measurements are in 62368-1 is that the limits are based on IEC Guide 117, Electrotechnical equipment - Temperatures of touchable hot surfaces, and its reference standards, which includes research only conducted in 25 C ambient.

Clause 10 Radiation

For equipment within the scope of IEC 62368-1 that incorporates radiating ultrasound or ultrasonic functions, is it required to document the ultrasound radiation as an RS1/RS2/RS3 energy source?

More specifically you asked (edited for clarity): For devices that are within the scope of IEC 62368 that incorporate radiating ultrasound or ultrasonic functions, is it required to document the ultrasound radiation as an RS1 / RS2 /RS3 energy source? This is for non-medical purposes with a max. sound level of 85 dBA.

In response, IEC 62368-1 and UL 62368-1 Second and Third Editions do not cover ultrasound or ultrasonic requirements in Clause 10 (Radiation) - only radiation hazards, such as Laser, LED, IR and UV are addressed, as well as X-Ray and Acoustic Pressure. (For acoustic pressure, the requirements only apply to Portable Music Players, and there is an average sound pressure limit not to exceed 85 dB(A).)

For a construction or technology not anticipated by IEC 62368-1, sub-clause 4.1.5, Constructions not specifically covered, would be used, which states, "Where the equipment involves technologies, components and materials or methods of construction not specifically covered in this document, the equipment shall provide SAFEGUARDS not less than that generally afforded by this document and the principles of safety contained herein,” in addition to, “The need for additional detailed requirements to cope with a new situation should be brought promptly to the attention of the appropriate committee.”

Therefore, since radiating ultrasound or ultrasonic functions are not covered by Clause 10, further research would be required to identify appropriate requirements and limits for device having ultrasonic or ultrasound features. Possible areas for research are, but are not limited to CTL Decisions (e.g., Sheet # 354 acc. IEC 61010-1; see https://decisions.iecee.org); or particular requirements of IEC 60601-x; or particular requirements of IEC 60335-x, etc.

Also, ideally, as a manufacturer producing such equipment falling under the scope of IEC 62368-1, in accordance with 4.1.5 you should consider making a proposal to IEC TC108 via your National Committee on how Clause 10 should address such equipment.

The complete answer to this topic is complex, and there appears to be a specific, detailed construction that needs review/analysis. Therefore, you are encouraged to contact UL Solutions for an in-depth consultation via https://www.ul.com/services/iec-62368-1-testing-certification.

Annex B Normal operating condition tests, abnormal operating condition tests and single fault condition tests

Does Annex B.2.6.2 in EN 62368-1 force one to perform temperature measurements for Cause 6 at real Tma (manufactures max allowed ambient temperature of the DUT)?

More specifically you asked (edited for clarity): Does B.2.6.2 in EN 62368-1 force to perform temperature measurements for Cause 6 at real Tma (manufactures max allowed ambient temperature of the DUT), or is it allowed to perform measurement at 25 C and calculate the resulting temperature at components and parts?

B.2.6.2 covers heating test options for temperature dependent equipment as opposed to non-temperature dependent equipment, which B.2.6.3 covers. For temperature dependent equipment, B.2.6.2 provides two options. As noted, the temperature can be measured in an oven at the least favorable temperature as declared by the manufacturer, but not exceeding Tmax. Alternatively, the temperature can be measured in room ambient (e.g., 25 C) with the heating or cooling device at the least effective setting or defeated, again which would need to be identified by the manufacturer.

For compliance with B.2.6.2, because of the nature of equipment designs that incorporate active temperature dependent heating/cooling, including fans that adjust to sensed temperatures, it is not appropriate to adjust temperatures as can be done for passive non-temperature dependent equipment per B.2.6.3.

Due to the variety of active cooling/heating designs that can be associated with B.2.6.2, usually the application of B.2.6.2 requires collaborative discussion between UL Solutions and the manufacturer due to the need to determine worst case conditions for temperature dependent equipment.

Annex B Normal operating condition tests, abnormal operating condition tests and single fault condition tests

Which are the temperature limits during the abnormal operating conditions?

More specifically you asked: What are the temperature limits during the abnormal operating conditions? In 5.4.1.4.3 of IEC 62368-1 there are the temperature limits during the normal operating conditions (see Table 10), but we can't find the temperature limits during the abnormal operating conditions, in particular for electronic component and insulating materials. In IEC 60065 there is Table 3 "Permissible temperature rise of parts of the apparatus" which is very clear and there are 2 columns, one for "Normal operating conditions" and another one for "Fault conditions". In B.4.8 of IEC 62368-1 there is the requirement: "During and after single fault conditions, any flame inside the equipment shall extinguish within 10 s and no surrounding parts shall have ignited". It seems that there is no temperature limit: can you confirm?

In response, in IEC 62368-1:2014 and IEC 62368-1:2018, temperature limits under abnormal conditions depend on the energy source being classified, i.e. Clause 9 - Thermal burn injury; and for components, the function as a component safeguard.

In IEC 60065 Ed. 8, all temperature limits were documented primarily in Table 3.  In IEC 62368-1:2018, temperature limits are associated with the energy source and a component when it functions as a component safeguard.

For touch temperatures, classification is done considering normal, abnormal and single fault conditions. The TS classification (and its associated maximum temperature) depends on application, intended user and user access.

For component safeguards, requirements for these components, devices and/or sub-assemblies, are detailed in the identified annexes/subclauses for the components, e.g. Transformers, subclause G.5.3

In 62368-1 there is not a single location that specifies all maximum temperatures with their associated condition and component. Hazard based engineering was used to develop the requirements, so the applicable limits are associated with the energy source and/or application.

Annex B Normal operating condition tests, abnormal operating condition tests and single fault condition tests

Does the "any two leads" short exemption in B.4.1 apply to all pins on the current limiter IC complying with Annex G.9, or is only the requirement for shorting input to output waived as is implied in G.9.1?

More specifically you asked: B.4.1 offers an exemption from short-circuit tests between any two leads for current limiters complying with clause G.9. G.9 states that for PS1 or PS2 IC current limiters input and output will not be shorted if the IC is compliant. Does the "any two leads" short exemption in B.4.1 apply to all pins on the current limiter IC, or is only the requirement for shorting input to output waived as is implied in G.9.1?

In response, Clause B.4.1 generally guides the consideration for single fault conditions of components, including component failure simulation, by a short-circuit of two leads at a time and open-circuit of one lead at a time. However, as you note, B.4.1 also has a general exception for integrated circuit current limiters complying with Clause G.9.

As you also note, in G.9.1 (IEC 62368-1:2018) it more clearly states, “IC current limiters used for current limiting in power sources so that the available output power becomes PS1 or PS2 are not shorted from input to output if they comply with all of the following.”

Therefore, it appears that the main emphasis of B.4.1 and G.9.1, when considered together in the context of IC current limiters, is the consideration of a short-circuit between input and output pins only, which makes sense for an IC current limiter because a short-circuit between input and output leads is considered to be the worst-case component failure condition as it disables the entire protective (safeguard) function of the output current and power control.Such a safeguard function is required by 6.5.2, Requirements for interconnection to building wire, and 6.6, Safeguards against fire due to connection of additional equipment, via their reference to Annex Q, Circuits intended for interconnection with building wiring, which in turn references G.9 as an option.

However, we need to remember, Annex B also is referenced in other parts of IEC 62368-1, including other sub-clauses in Clause 6, such as 6.4, Safeguards against fire under single fault conditions. Does the IC current limiter exception in B.4.1 apply for these applications too?

In these cases, since the IC current limiter itself could be a potential source of ignition, it would seem that the short-circuit of two pins should be a consideration, even though the IC Current Limiter complies with Clause G.9. (It is noted that “risk of ignition / fire” is not a compliance criteria in G.9.3, only that “the device shall limit the current in accordance with its specification as applicable or the device shall become open circuit.”)

Your question identifies an area of the IEC 62368-1 standard that may need some further clarification/refinement by IEC TC108.

Annex B Normal operating condition tests, abnormal operating condition tests and single fault condition tests

Can single fault condition testing between pins of a control IC and power switching MOSFET in a single package be omitted if there is inherent isolation between both complying with Basic Insulation requirements?

More specifically you asked (edited for clarity): some AC/DC switching power supply circuits in IT/AV products are constructed using unrecognized off-line switcher IC components that incorporate the control IC and power switching MOSFET into a single IC package. Typically, the chip is designed to provide isolation between the drain/source pins of the MOSFET, and the control pins. Question: Is it always necessary to complete single fault testing between the control pins and drain/source pins of the MOSFET per B.4.1, or can omitting faults between the Drain/Source Pins of the MOSFET and the control pins of the IC be justified if the isolation between the Drain/Source pins and control pins (including PCB traces) meets creepage/clearance or electric strength requirements for BASIC INSULATION in accordance with B.4.4.1 and B.4.4.2?

In response, it is our understanding that the switcher IC and MOSFET you describe function independently, but are isolated in the same IC package by equivalent to Basic Insulation.

Based on this understanding, in most cases, the short circuit between the pins of the switcher IC and MOSFET may not be required per clause B.4.4 of IEC 62368-1:2014 and IEC 62368-1:2018 since the isolation possesses a certain quality (clearance, creepage distance and electric strength) comparable to a Basic safeguard.

However, IEC 62368-1 is a hazard-based standard and the application of Annex B needs to be considered in the context of the Clauses (covering different energy sources/hazards) that reference it - Annex B is not applied independently.

Faulting the Basic insulation should not be required in the context of Clause 5, Electrically-cause Injury, since Functional Insulation only is required as a minimum for such an IC package.

However, in Clause 6, Electrically-caused Fire, if the “Reduction of the likelihood of ignition” method is chosen, then, in accordance with the sub-clause 6.4.3 of IEC 62368-1:2014 or IEC 62368-1:2018, relevant single fault condition testing is required across a single safeguard in the context of risk of fire. In accordance with the definition of a Single Fault Condition (3.3.7.9) and B.4.1, Simulated single fault conditions - Generally, a basic safeguard failure should be considered if it affects the safety of the equipment. Therefore, we believe a single fault condition across the single safeguard is appropriate in this situation.

Your question points to an area of IEC 62368-1 that may need further refinement and we encourage you to engage IEC TC108 through your National Committee if you believe the Standard needs further clarity on this topic. Also, as this forum is a general forum and is not intended to analyze and provide guidance on specific designs, you are encouraged to contact UL Solutions for an in-depth consultation via https://www.ul.com/services/iec-62368-1-testing-certification.

Annex F Equipment markings, instructions, and instructional safeguards

When a product is marked with an IP rating, does that automatically make the product an outdoor product and invoke all the requirements of Annex Y, or can an indoor product be marked with an IP rating too?

More specifically, you asked (edited for clarity): Does declaring an IP rating in the IEC 62368-1 Test Report Form (TRF) make the product an outdoor product, automatically triggering all the Annex Y requirements for outdoor use equipment? Can an indoor product also be evaluated for and marked with an IP rating?

In response, IEC 62368-1:2023’s Clause F.3.7, Equipment IP rating marking, in its Annex F, Equipment markings, instructions, and instructional safeguards, states, “Where an IP construction is used as a safeguard: –the safeguard shall be in accordance with IEC 60529; and –the IP code shall be declared in the instruction manual or on the equipment.”

The intent of IEC TC108 adding this requirement to the standard outside of Annex Y is that not all uses of IP ratings are associated with outdoor use equipment. However, if the equipment is rated/marked so, it is required to comply with the appropriate requirements for the IP rating, i.e., appropriate evaluation per IEC 60529, Degrees of protection provided by enclosures (IP Code).

For example, if a transceiver is intended to be installed in an enclosed public parking garage, possibly subject to wet contact due to spraying water during washing or similar activity, the manufacturer may want to declare an IP rating without qualifying the transceiver as an outdoor use equipment. In this case, the transceiver would be marked per F.3.7, and investigated to IEC 60529 appropriately, without having to be subjected to all the Annex Y requirements for outdoor use. The information added to the IECEE TRF (UL Report) would be documented accordingly.

As this forum is not intended to analyze and provide guidance on specific designs, we recommend that you contact UL Solutions and request an in-depth consultation if you have a specific design or construction that you would like to discuss.

Annex F Equipment markings, instructions, and instructional safeguards

In UL 62368-1, Third Edition, Annex F.3.3.9DV.1, do the words "output terminals" apply to standardized computer interfaces / connectors such as a USB-C PD port?

More specifically you asked: UL 62368-1 F.3.3.9DV.1 requires that output terminals provided for supply of other equipment except mains supply shall be marked with the nominal output voltage and frequency and, in addition, the maximum output current or power, unless the terminals are marked with the type references of the equipment which are permitted to be connected. If this requirement is applied to standardized computer interfaces / connectors such as a USB-C PD port, what voltage and frequency shall be marked on the product given the range of DC (0 Hz) voltages that might produce based on negotiation with an attached device?

In response, National Difference F3.3.9DV.1 has been in CSA UL 62368-1 since its Edition 1 (F.3.3.8DV.1) and is intended to apply to equipment with ‘terminals’ (e.g., Field Wiring Terminals) that need to be hard-wired to supply power to other equipment. Therefore, this requirement does not apply to standardized computer interfaces / connectors supplying power to other AV/ICT equipment, such as a USB PD port, which supplies power to other AV/ICT equipment in close proximity. For a USB PD port, which is a standardized interface, the importance of communicating the information required for terminals that is in F.3.3.9DV.1 is less important.

However, we make note, for interfaces connected to “building wiring”, including PoE, there are requirements in Article 725, Class 2 and Class 3 Power-limited Circuits, that would apply to these standardized interfaces / connectors, such a PoE. In the 2023 NFPA 70, National Electrical Code (NEC), its Section 725.60(C), Power Sources for Class 2 and Class 3 Circuits - Marking (Section 725.121(C) of the 2020 NEC) contains a marking requirement that includes information similar to F3.3.9DV.1. In CSA UL 62368-1, see Annex DVA (Q), Power sources for Class 2 circuits, for more details on the marking as it applies to AV/ICT equipment with PoE.

Annex F Equipment markings, instructions, and instructional safeguards

When are POE and USB ports required to be marked with the output voltage and the output current according to CSA UL 62368-1 F.3.3.9DV.1? For POE, can we mark "POE" or "POE+" etc. to replace voltage and current?

More specifically you asked (edited for clarity): UL 62368-1 F.3.3.9: Output terminals provided for supply of other equipment except mains supply shall be marked with the nominal output voltage and frequency and, in addition, the maximum output current or power, unless the terminals are marked with the type references of the equipment which are permitted to be connected. According to our understanding of the sentence "unless the terminals are marked with the type references of the equipment," for POE we will add "POE" or "POE+" or "POE++" near the POE port. For USB, we will add USB 2.0 symbol or USB 3.0 symbol near the USB port. Can you confirm whether the strategy can meet the requirement of UL 62368-1 and the NEC (National Electrical Code)?

In response, first let's clarify that National Difference, F3.3.9DV only is intended to apply to equipment with “terminals” that need to be hard-wired to supply power to other equipment. This marking has been in CSA UL 62368-1 since its Ed. 1 and this marking was not intended to apply to USB, PoE and similar standardized ports with standardized connectors. However, now there are other newer requirements in CSA UL 62368-1 that apply to some of these ports.

More specifically, based on new requirements in Section 725.121 of the 2017 NFPA 70 (NEC), there is a new marking that applies to output ports that supply power (Class 2 or LPS) to other equipment through long lengths of cables (building wiring). Please look closely at 725.121(A)(4) and 725.121(C), which require certain outputs supplying building wire, such as PoE, to have maximum voltage and current markings or labels so cable installers (electricians) can correctly size the cabling, in particular bundled cables, in accordance with new NEC Section 725.144, Transition of Power and Data. CSA UL 62368-1 Ed. 3 now covers this NEC requirement in regulatory annex, Annex DVA (Q), Power Sources for Class 2 circuits. Note, there is an exception to this marking / labeling for power sources providing 0.3 amperes nominal current or less (based on a Tentative Interim Agreement (TIA) that was issued by NFPA after the 2017 NEC was published).

Therefore, for your example (POE output port), it now will need to comply with above National Difference in Annex DVA. However, marking the PoE port as “POE" or "POE+" etc. does not meet the requirement since it does not allow for the equipment to comply with the installation requirements in NEC Article 725, i.e., the cable installer (electrician) and / or Authority Having Jurisdiction (AHJ) will be looking for the maximum voltage and current to be marked or labeled so they can determine compliance of the installed cabling with new Section 725.144. Note, for the 2020 NEC, there is some further refinement of the requirements in 725.121 (and further refinement in the 2023 NEC). We suggest you review them and consider them into your designs.

Please note too, Annex DVA (Q) only applies to output circuits/ports connected to building wiring. Generally, “USB” is intended to be used for relatively short interconnects between equipment and not for connection to building wiring. Therefore, generally, USB ports are not covered by the NEC Article 725.121 and Annex DVA (Q). As a result, for USB the output voltage and output current are not required to be marked as for PoE.

Annex F Equipment markings, instructions, and instructional safeguards

What are the options for marking limited power outputs, e.g., PoE ports, per the NEC Section 725.121(C)?

More specifically you asked (edited for clarity): When are PoE ports required to be marked with the output voltage and the output current according to requirements in Section 725.121 of the 2017 NFPA 70 (NEC) and CSA UL 62368-1 Ed. 3 Annex DVA (Q)? For some products, there is not enough space next to the POE port of the equipment to mark the voltage and current. Therefore, can we use the one of following ways instead of being marked on equipment: 1-Output marked in the manual. 2-Add a note in the test report such as: the POE output can't be connected to building wiring. 3-Other ways.

In response, since the complete answer to this question will depend significantly on the specific construction under consideration for application of NEC Section 725.121(C) and Annex DVA (Q), you are encouraged to contact UL Solutions for an in-depth consultation via https://www.ul.com/services/iec-62368-1-testing-certification.

However, in the meantime, below are a few considerations:

• NEC 725.121(C) allows for a single marking to cover multiple ports, and it does not indicate exactly where the label must be placed. Therefore, there may be additional ability to meet the requirement than you indicated. Also, Annex DVA (Annex Q) currently allows for such a label to be supplied with the equipment, and to be applied at the installation, so this may be another option.
• There is no stipulation in the NEC that the required marking can be in a manual, which is reasonable since the information in the marking will be used by electricians wiring per the NEC and Authorities Having Jurisdiction (AHJ) inspecting the equipment for compliance with the NEC. The needed information located in a manual may not be helpful.
• Building wiring is a term used in 62368-1 and is not specifically used in NEC Article 725. However, if the specific equipment with PoE ports will use a wiring method (e.g., Listed CL2 cable) covered by Article 725 (or 840), it would be considered building wire per UL 62368-1. Most PoE ports will use Article 725 wiring methods, so the proposal to add into the test report that the PoE can't be connected to building wiring would not be a reasonable solution in most cases.

Please also review the content of the current Annex DVA (Annex Q) National Difference for NEC Section 725.121(C).

“If applicable based on 725.121(C) being required for the equipment, limited power sources for listed audio/video, information, and communications technology (equipment) covered in 725.121(A)(4) shall have a label indicating the maximum voltage and maximum current, or the maximum voltage and nominal current output for each connection point. Where multiple connection points have the same rating, a single label may be used. The marking shall not be required for power sources providing 0,3 amperes nominal current or less per conductor. The marking shall be provided on the equipment, permanently, or shall be provided with the equipment for permanent application and ready inspection after installation. Other options for the manufacturer to supply this information to the installer and fulfill the provisions of the NEC and CE Code, Part I, may be considered at the discretion of the manufacturer.”

Annex F Equipment markings, instructions, and instructional safeguards

Does an Optical Isolator that meets IEC 60747-5-5 as required under sub-clause G.12 of IEC 62368-1 need to fulfill the creepage distance requirements along outer component surface according to 5.4.3?

More specifically you asked (edited for clarity): For use of optocouplers according to Clause G.12: If we are using an opto device with IEC 60747-5-5 approval present, with a V(ini,a) value that is greater than the electric strength requirement as per 5.4.9.1, does the requirement still remain for a minimum external creepage distance to be present along the component body, or is compliance assumed due to complying with Clause G.12, thus allowing in application to use a reduced external creepage distance than Clause 5.4.3 would usually allow?

In response, per sub-clause 5.5.4, for Optical Isolators used as a Safeguard (according to sub-clause 5.5), the Insulation of the component shall comply with the requirements of 5.4 or with G.12.

When the Optical Isolator is used as Safeguard providing Supplementary or Reinforced Insulation according to sub-clause 5.4.4.4 and it meets G.12, such a component has no minimum internal Clearance or Creepage Distance, and no minimum distance through insulation requirement. However, as you stated, the referenced initial test voltage V(ini a) of the Optical Isolator must be at least equal to the appropriate test voltage in 5.4.9.1.

The above requirements apply to the Insulation of such Optical Isolators related to internal spacings. However, the evaluation of the distances along the component outer surface in combination with the final end-product construction still applies. Therefore, specifically for Creepage Distances, appropriate external Creepage Distances according to 5.4.3 still apply.

Annex F Equipment markings, instructions, and instructional safeguards

For ITE intended for installation in a restricted access location, may the electrical ratings be placed in the installation guide rather than marked on the product if a symbol near the appliance inlet refers to the installation guide?

More specifically you asked: For IT equipment with appliance inlet (not the direct plug-in) deployed in restricted accession location specifically accessed by instructed and skilled persons, if there is no place to affix the input rating (voltage, current, frequency) on equipment, can we use instruction safety guard near the appliance inlet so that user can refer to the required input ratings in the HW installation guide?

In response, there is no current basis in sub-clause F.3.3 of Annex F of UL IEC 62368-1 for allowing electrical ratings (for mains connected equipment) to be in the manual/installation guide if replaced by a symbol(s) on the product (such as symbols ISO 7000-0434 (2004-01) / ISO 7000-1641 (2004-01) that refer to the text in an accompanying document). There also are no special provisions on this topic for equipment installed in restricted access locations (RAL). 62368-1 allows for instructional safeguards/markings to be in manuals only when specified.

In North America, if attempting to do so, there would likely also be inspection issues by Authorities Having Jurisdiction (AHJs) / Electrical Inspectors because nameplate information/ratings are not only used by skilled or instructed persons - Electrical Inspectors check electrical ratings to confirm branch circuit (mains) loading, etc. Therefore, such ratings/markings are expected to be on the equipment.

Also, if the equipment is likely to be installed in a Data Center (which is considered a RAL), Article 645 of the U.S. National Electrical Code (NEC) is explicit in Section 645.16, Marking, - “Each unit of an information technology system supplied by a branch circuit shall be provided with a manufacturer’s nameplate, which shall also include the input power requirements for voltage, frequency, and maximum rated load in amperes.”

If the submitter believes that IEC 62368-1 should be revised to allow for a wider consideration of electrical ratings provided in installation manuals, the submitter should consider making a proposal (w/technical rationale) through their National Committee associated with IEC TC108.

Annex F Equipment markings, instructions, and instructional safeguards

For the IEC 60417 symbols in CSA UL IEC 62368-1, such as the IEC 60417- 5041 symbol, is there any minimum size requirements for the symbol or the text adjacent to the symbol such as "HOT SURFACE"?

In IEC 62368-1, the only normative mention of legibility is in Annex F, sub-clause F.3.9, Durability, legibility and permanence of markings - it states, “In general, all markings required to be on the equipment shall be durable and legible, and shall be easily discernable under normal lighting conditions.”; and “Compliance is checked by inspection.” (There is no CAN US National Difference on the topic in CSA UL 62368-1.)

IEC TC108 did not provide more specificity due to the hundreds (probably thousands) of product and component types covered under IEC 62368-1, making it impractical to provide minimum size requirements for all applications. During a product investigation, an NCB may call into question a marking that appears not legible or not easily discernable under normal lighting conditions, but the level of concern also would hinge on whether the marking is an instructional safeguard (e.g., caution marking) or informational (e.g., nameplate). Over the years, there have been nameplate markings accepted on AV/ICT products (including grey-black nameplate ratings on external power supplies (bricks) and nameplate ratings on small power adapters) that some may consider as marginally meeting the “legible” and “easily discernable under normal lighting conditions” criteria. However, this concern has not been problematic with instructional safeguards (caution markings).

If a manufacturer wants more guidance on the topic than IEC 62368-1, they may consider reviewing the ANSI Z535 series standards (including Z535.4) for additional help https://www.nema.org/standards/z535/ansi-z535-brief-description-of-all-six-standards-and-safety-color-chart.

Annex G Components

For IEC 62368-1's Annex G.9 on IC current limiters, one of the stated conditions is that the IC is supplied by a source whose output does not exceed 250VA. Can you provide some background on this change?

Annex G.9 was overhauled in Edition 3 of IEC 62368-1, including a new test program replacing the previous three test programs. A 250VA power source is to be used for testing, unless the IC CL manufacturer specifies something less, which then will be documented as part of the certification as a component consideration.

Annex G Components

For IEC 62368-1 and IECEE CB Reports to it, are IEC 60127-1 fuses required?

Generally, yes, but there is more to be aware of than a simple yes or no answer.

As we know, the IECEE CB Scheme is a global data exchange program that is used to reduce redundant evaluation/testing. IEC standards are the base standards used by Certification Body Testing Laboratories (CBTLs), with review by National Certification Bodies (NCB), to provide/issue IECEE CB Test Reports (TR) and Test Certificates (TC).

IEC standards typically require IEC fuses, such as IEC 62368-1 specifying IEC 60127-1. Therefore, IEC 60127-1 and similar IEC fuses can be considered the norm in the IECEE CB Scheme for most electrical products.

However, in the IECEE CB Scheme, manufacturers can, and typically do, ask that National Differences be considered in the investigation by the NCB because the manufacturer is planning to use the CB Report for obtaining marks in multiple countries (global market access). Therefore, most IECEE CB Reports include addendums that cover the National Differences for the multiple countries covered by the CB Report. The National Differences are from the National Standard based on the IEC Standard, such as our bi-national standard, CSA UL IEC 62368-1, for CAN/US.

Most countries do not have National Differences from the IEC standard for fuses. Therefore, most countries require IEC 60127-1 and other IEC fuses as specified in them. However, there can be exceptions.

For example, for CAN/US in CSA UL IEC 62368-1, there is a National Difference for fuses used for Branch Circuit protection because of electrical code (NEC & CEC) requirements for protection of branch circuits/receptacles. However, there is no National Difference for fuses used for Supplementary Protection inside products since the electrical codes do not cover such applications.

Therefore, for AV/ICT equipment for CAN/US, if a fuse is used in a product for a branch circuit application (e.g., protecting a NEMA receptacle in a PDU), Annex NAE of CSA UL 62368-1 requires UL 248-x or CSA 248.x fuses.

However, if a fuse is used in a product in a supplementary protection application (e.g., front end of SMPS), IEC 60127-1 is fine, although per Annex NAF a fuse complying with UL 248-14 or CSA 248.14 also is acceptable for CAN/US only.

(Similar requirements are in Annex NAE & NAF for Circuit Breakers & Supplementary Protectors.)

Annex G Components

I have a question on a GDT connected in series with an MOV in Type A pluggable equipment and how this construction impacts application of 5.5.7, G.8.1 in the context of post-production Hi-Pot testing at 1.5 kv.

More specifically you asked (edited for clarity): IEC 62368-1 requires a GDT to be connected in series with any MOV used in a L-PE and N-PE protection for the usual Type A pluggable equipment (5.5.7) and the GDT used must withstand the Basic Insulation voltage withstand requirement (5.4.9.1, 2.5 kV for 230 V a.c.). Given the GDT requirement, was it the intention of IEC 62368-1 to render the tests of G.8.1, G.8.2 and G.8.3 benign, so that no testing is necessary, and the post-production Hi-Pot test of 1.5 kV a.c. can be passed with ease?

In response, the submitted question on SPD requirements per 5.5.7 and Varistor requirements per Annex G.8 of IEC 62368-1 appears to be combining or confusing considerations for Type investigation/test requirements and Routine electrical safety testing in production. This is not the intent of IEC TC108.

Since the focus seems to be with the GDT, specifically per 5.5.7, the GDT is required to comply with the electric strength test of 5.4.9.1 for basic insulation; and the external clearance and creepage distance requirements of 5.4.2 and 5.4.3 respectively for basic insulation.

For a Type investigation/test, this testing on the GDT is performed on the GDT and not the entire product. Therefore, compliance with the GDT with 5.5.7 can be wholly determined during the Type investigation.

Similarly, compliance with Annex G.8 for the Varistors can be determined during the Type investigation.

Regarding Routine testing, generally this testing is conducted to detect manufacturing failures (e.g., miswiring in product) and unacceptable tolerances in manufacturing and materials. In fact, this is stated in the Scope of IEC 62911, Audio, video and information technology equipment '“ Routine electrical safety testing in production, also produced by IEC TC108.

The intent of Routine testing is not to attempt to reconfirm compliance of the equipment with every requirement considered during the Type investigation/testing.

IEC 62911 also states in Clause 4, Conformance, “Practical measures can be used to conduct the test, such as finding an appropriate way to make the connections necessary to perform the relevant test.” This principle often has to be applied during Routine testing due to the variety of equipment and constructions subjected to the limited routine tests (typically limited to resistance of protective bonding and electric strength).

However, in the case of a GDT & Varistor in series, during Routine testing on a product level there would be nothing gained from a safety perspective attempting to conduct a mains to protective earth electric strength test under special conditions, so typically the GDT & Varistor are tested in the product without modification even if it means that part of the circuit, including MOV, may not experience the full 1.5 kV electric strength test during routine test.

If there are concern with the current set of requirements in either IEC 62368-1 or IEC 62911, it is recommended that IEC TC108 be engaged via participation in your national committee.

Annex G Components

Does IEC 62368-1's Annex G.8 allow me to test the combination of varistors rather than individual varistors?

More specifically, you asked: By connecting two varistors in series I can manage the single fault criteria. Does IEC 62368-1’s Annex G.8 allow me to test the combination rather than individual varistors? Both G.8.2.2 and G.8.2.3 state a varistor or a surge suppression circuit containing varistors.

In response, some varistors and their surge suppression circuits will need to be subjected to overload and temporary overvoltage testing as explained in G.8.3.2 and G.8.3.3 of IEC 62368-1 Edition 2 and now in G.8.2.2 and G.8.2.3 of IEC 62368-1 Edition 3. Both IEC 62368-1 Edition 3 and IEC 62368-1 Edition 2 allow for the tests in G.8 to be performed on the circuit containing the varistor. Regarding single fault criteria, keep in mind, for some constructions as explained in sub-clause 5.5.7, a gas discharge tube (GDT) in series with the varistor is required. Thus, the opening or shorting may not be an issue. As this forum is not intended to analyze and provide guidance on specific designs, you are encouraged to contact UL Solutions for an in-depth consultation via https://www.ul.com/services/iec-62368-1-testing-certification.

Annex G Components

Can a battery charger be qualified as an IC current limiter under clause G.9?

More specifically you asked: Can a battery charger be qualified as an IC current limiter under clause G.9 - i.e., can a whole battery charger circuit (including all the discrete electronic components) be considered as an IC current limiter and can this circuit be tested according to G.9?

In response, first, we will have to assume that the battery charger you mentioned is the IC controller and related discrete components to control the charging voltage / current to a downstream device with batteries. The following answer is based on this assumption.

Sub-clause G.9, Integrated circuit (IC) current limiters, is only suitable for single semiconductor devices (containing numerous integral components) and not for discrete electronic components that may comprise of a circuit that also provides current limiting. Since fault testing cannot be applied inside the semiconductor devices, except on the external IC pins, in order to assess the reliable performance/function of the IC, the 62368-1 standard has a performance-based test program (G.9) for IC current limiters to verify the reliable performance/function.

However, for other circuits consisting of discrete electronic components, the reliability of whole circuit to perform a safeguard function can be determined by single-fault testing. Therefore, single fault tests typically are conducted on selected components to verify the performance/function of this circuit to act as a safeguard, such as if it is being used to meet the requirements in sub-clause Q.1, Limited power source, in Annex Q, which requires that if a regulating network is limiting the output, simulated single faults are conducted within the regulating network. Therefore, for circuits with discrete electronic components, compliance with sub-clause Q.1 in Annex Q is appropriate and not sub-clause G.9.

The complete answer to this topic is complex, and there appears to be a specific, detailed construction that needs review/analysis. Therefore, you are encouraged to contact UL Solutions for an in-depth consultation via https://www.ul.com/services/iec-62368-1-testing-certification.

Annex G Components

When AV / ICT equipment utilizes an a.c. rated fuse in a d.c. circuit, what level of investigation is required to determine if an a.c. rated fuse is acceptable for use in a d.c. circuit?

The preferred position regarding any fuse relied upon for safety is that the fuse be suitably rated for the application. Therefore, manufacturers are encouraged to use d.c. rated fuses in d.c. circuits.

However, components may be used outside of their ratings if it can be determined that the use of a component outside of its rating does not introduce a hazard during the operation or servicing of the equipment, i.e., application of concepts per the 4th dashed paragraph of sub-clause 4.1.2 of IEC 62368-1:2018 and UL 62368-1:2019 (Ed. 3).

To acknowledge the difference in nature between a.c. and d.c. circuits, a.c.-only rated fuses used in d.c. circuits should demonstrate their capability for use in d.c. applications by means of performance-based type test program (which also may include a periodic follow-up test program).

(These considerations are documented in a previous UL Solutions Practical Application Guideline (PAG), 2.7-2, AC rated fuses used in DC circuits, which was associated with UL IEC 60950-1, but from which the principles still remain valid.)

In the PAG an exception is allowed for fuses that are UL Solutions Listed / Recognized for 120 V a.c. minimum and that are used in circuits having a maximum 36 V d.c. Based on published literature and empirical research performed by UL Solutions SMEs in the fuse industry sector, for d.c. circuits with a nominal open circuit voltage of 36 V d.c. maximum, d.c. arcing is not considered sustainable at these voltages. Therefore, a.c. fuses rated minimum 120 V a.c. are found capable of performing the intended protection of these circuits safely and consistently.

In the IECEE CB Scheme for IEC 62368-1, Recognizing NCBs may have additional requirements for acceptance and evaluation. Therefore, based on the specific construction, in the Scheme there may be differing approaches for compliance with IEC 62368-1 versus a certification program like UL Solutions Mark, GS Mark, etc.

The complete answer to this topic is complex, and there appears to be a specific, detailed construction that needs review/analysis. Therefore, you are encouraged to contact UL Solutions for an in-depth consultation via https://www.ul.com/services/iec-62368-1-testing-certification. Via this consultation we can review the specific details of use of an a.c. rated fuse in a d.c. circuit in your product / construction and discuss the potential additional test and follow-up service requirements, if any.

Annex G Components

Can the requirements for protection of wound components against mechanical stress in G.5.1.2 be waived if an Insulation System is used according UL 1446?

More specifically you asked: When two winding wires, or one winding wire and another wire, are in contact inside the wound component, crossing each other at an angle between 45 degrees and 90 degrees without mechanical protection, can Annex G.5.1.2 not be required if the transformer has an insulation system (UL 1446)?

In response, transformers used as safeguard providing Basic, Supplementary or Reinforced Insulation are required to comply with G.5 as referenced in 5.5.3 and 5.4.4.7. Also, per 5.4.1.4.3, if the measured temperature exceeds Class 105(A) limits, they are required to have a suitable insulation in accordance with IEC 60085, or UL 1446 (according to Annex DVF 5.4.1.4.3).

Sub-clause G.5.1.2 includes both a prescriptive option and a performance option (endurance test per G.5.2).

As noted in compliance criteria in G.5.1.3, there are special allowances for wires tested per Annex J. Such wires (sometimes also known as “Triple Insulated Wires”) that meet Annex J are UL certified under the category OBJT2 (Single- and Multi-layer Insulated Winding Wire) - see also the requirements in Annex DVF Annex J that such wires should meet UL 2353.

Insulation Systems that meet IEC 60085 can be found in UL Product iQ® under the category ODCA2 (Insulation Systems, Electrical, Certified to IEC Publications), while Insulation Systems according UL 1446 are certified under OBJY2 (Systems, Electrical Insulation). Such Electrical Insulation System (EIS) certification covers exclusively the evaluation of the chemical compatibility of material used in a system. Electrical testing, such as temperature or overload testing, on the final wound transformer are not included, in addition to there being no construction analysis. These mechanical / electrical requirements need to be based on the individual standard used for the end-product certification, such as UL IEC 62368-1.

Therefore, the answer to the question is no, use of an UL 1446 System does not waive the mechanical requirements in G.5, neither the prescriptive nor performance option.

Annex G.4 Connectors

What are the requirements for wiring connectors for connection of protective earthing?

More specifically, you asked (edited for clarity): Should ring lugs that are intended for connection to mains protective earth by protective earth (ground) wire be UL 486A, UL 486B certified?

In response, for connectors associated with permanent connection to the mains, which includes those associated with protective earthing, per CSA UL 62368-1’s Annex DVE (mandatory UL and CSA component Requirements), Sub-clause G.4.3, Wiring terminals, the connectors are required to comply with UL486A-486B or one of the other standards listed in Annex DVE (G.4.3). This requirement is driven by the National Electrical Code (NEC), Section 250.8, Connection of Grounding and Bonding Equipment.

For such connectors not directly associated with the mains, such as protective earthing/bonding inside the equipment after an appliance inlet, per Annex DVF (Alternative UL and CSA component requirements) Sub-clause 5.6.5.1, Wiring terminals, the connectors may comply with UL 486A-486B or one of the other standards listed in Annex DVF (5.6.5.1) as an alternative to the construction and performance requirements in the base sub-clause 5.6.5, Terminals for protective conductors.

As this forum is not intended to analyze and provide guidance on specific designs, we recommend that you contact UL Solutions and request an in-depth consultation if you have a specific design or construction that you would like to discuss.

Annex G.7 Mains supply cords

Do the requirements in IEC 62368-1:2023 Table G.7 apply to internal wiring supplied by the mains?

More specifically, you asked (edited for clarity): For AC wiring internal to the product (after the fuse at the power inlet), do the AWG requirements of IEC 62368-1 Table G.7 apply? Is there an alternate path to waive these requirements based on single fault testing or alternate standard that could be followed for multi wire cable assemblies?

In response, since the title of clause G.7 is Mains supply cords, generally Table G.7 only is applicable to (external) mains supply cords, unless referenced elsewhere in the standard, such as in Clause 6. For example, Clause 6 references Table G.7 for determining the suitability of the size of some protective conductors, or internal wiring supplying mains power to socket-outlets, which do not appear to be applications you ask about.

For internal wiring, in general, the suitability of the conductor size (AWG) is determined by the temperature of the insulation during Clause 5 heating tests, and its suitability to prevent risk of fire during Clause 6 and Annex B abnormal operation and single fault testing.

As this forum is not intended to analyze and provide guidance on specific designs, we recommend that you contact UL Solutions and request an in-depth consultation if you have a specific design or construction that you would like to discuss.

Annex G.11 Capacitors and RC units

In a power supply that has a filtering cap between Live (Line) and Neutral, upstream of the fuse on the live line, can that cap be an X cap, or does it have to be a Y cap?

Class X capacitors are suitable for use in designs where failure of the capacitor would not lead to increased risk of electric shock. If a capacitor is connected between line and neutral of the primary circuit connected to the mains supply, the failure, e.g., short-circuit, of the capacitor would not be expected to increase the risk of electric shock because the insulation bridged by the capacitor is considered functional insulation, even in this case if it is located upstream of the line fuse in the power supply unit. Therefore, a Class X capacitor can be used for this construction and a Class Y capacitor should not be required at the location in question. See Sub-clauses 5.5.2 and G.11 in IEC 62368-1:2018 for more details.

Annex G.13 Printed boards

What is defined as a 'suitable coating' in IEC 62368-1? Is a standard solder mask considered to be a suitable coating?

More specifically your asked: I can't find a proper definition of a 'coated board' in the 62368-1 standard. What is defined as a 'suitable coating'? Is a standard solder mask considered to be a suitable coating?

In response, there is no definition of a “coated board” or “suitable coating” in Clause 3 of IEC 62368-1:2023, the latest edition, or earlier editions. However, in relation to ‘suitable coating’, sub-clause G.13.3 of Annex G of IEC 62368-1 states the following:

“For printed boards whose outer surfaces are to be coated with a suitable coating material, the minimum separation distances of Table G.13 apply to conductive parts before they are coated.”

For application purposes, it is generally understood in IEC 62368-1 that a coated printed board that meets tests of G.13.6 of IEC 62368-1 is considered a printed board coated with a suitable coating material covered in G.13.3. Generally, a standard solder mask would not be considered a suitable coating material unless it complied with the test specified in G.13.6. However, even if a solder mask complies with G.13.6, it only would allow for reduction of Clearances and Creepage distances across the conductor pattern, which is different than a traditional conformal coating, which also may cover component leads, etc.

Also note that an alternative method to qualify coated printed boards is given in IEC 60664-3, which IEC 62368-1 permits per G.13.3.

Additionally, in the U.S. and Canada, compliance of a conformal coating with the UL 746 series is considered as an acceptable alternative to IEC 60664-3 according to Annex DVF (G.13.6) of CSA UL 62368-1.

Information on ULS Recognized Component Conformal Coatings can be located in the UL category, QMJU2, Coatings for Use on Recognized Printed Wiring Boards – Component. Please see UL Product iQ® for additional information. Use of a conformal coating in accordance with QMJU2 needs to be utilized in accordance with its conditions of acceptability and ratings.

Note too, QMJU2 has additional information on the difference between a Resist coating (solder mask) and Conformal coating. Please see below. Under QMJU2, a Resist coating is only tested for flammability, not as insulation, so it would not fulfill the requirements in G.13.3 of CSA UL IEC 62368-1.

“Resist coating, also known as solder resist or solder mask, is a material supplied in liquid or film form used to mask or to protect selected areas of a conductor pattern from the action of an etchant, solder, or plating, and remains on the printed wiring board after processing. Resist coatings have been tested for flammability with regards to the specific laminate and/or UL/ANSI type material indicated in the individual Recognition.

Conformal coating is an insulating protective coating that conforms to the configuration of the object coated, is applied on the completed board assembly to increase the dielectric voltage withstand capability between conductors and protects against environmental conditions. Conformal coatings are used on printed wiring boards in electrical equipment where electrical spacings are insufficient between uninsulated live parts of opposite polarity or between such parts and accessible dead-metal parts. Conformal coatings have been tested for flammability and dielectric properties (with regard to the effect of environmental, humidity and thermal conditions) for the specific laminate and/or UL/ANSI type material indicated in the individual Recognition. The environmental, humidity and thermal conditions are intended to emulate the end-use application.”

Annex G.13 Printed boards

If a UL Recognized Conformal coating (per UL CCN QMJU2) is applied on a recognized component printed wiring board, are the tests in UL 62368-1:2019 Ed 3’s Annex G.13.6 required on the coated printed board?

In response, the tests in Annex G.13.6 of UL 62368-1 are not applicable for coated printed boards with a UL recognized conformal coating (CCN:QMJU2) applied in accordance with the coating’s ratings and Conditions of Acceptability. In Annex DVF (G.13.6) of UL 62368-1, conformal coatings complying with UL746C (which refers to UL746E) are identified as an acceptable alternative to G.13.6 and IEC 60664-3. Thus, no additional tests from Annex G.13.6 are required for coated printed boards with such a UL recognized conformal coating being used. However, please note, the allowances covered in Annex DVF, UL and CSA component requirements (alternative to IEC standards), only apply for certifications associated with Canada and the U.S. If the same product would be covered by an IECEE CB Report investigated to IEC 62368-1, testing per Annex G.13.6 would be required.

Annex K Safety Interlocks

Could you explain more details about Annex K.7.1? Especially for the first 4 paragraphs? In actual practice, the interlock switch used in mains circuits hardly will have a 3mm contact gap. What should I do for this case?

Please note the requirements in K.7.1 have been rewritten in IEC 62368-1:2018 to try to eliminate some confusion in IEC 62368-1:2014 and to add more clarity.

As now stated in IEC 62368-1:2018, the requirements in K.7.1 are intended to address separation distance for contact gaps and interlock circuit elements. The requirements were modified to identify the scenario being addressed which is based on what the interlock is switching, if isolated from mains and the kind of hazard(s) involved, such as life-threatening or not. As an alternative to the separation distances, the standard allows for an electric strength test in accordance with 5.4.9.1 for basic or reinforced insulation as applicable.

Annex M Equipment containing batteries and their protection circuits

When a power adapter is used as a charger to charge an external Lithium-Ion battery or batteries, does Annex M.4 of IEC 62368-1 apply?

More specifically you asked: For an EPS (i.e., External Power Supply/Adapter) with no charging control circuit (i.e., has no way to monitor the temperature of the battery to stop the charging if the battery exceeds its maximum charge temperature) that is used to charge external Lithium-Ion batteries directly, when such EPS submitted for IEC 62368-1 evaluations, does Annex M.4 of IEC 62368-1 apply?

In response, we believe an important clarification may be in order. The question mentions the EPS charges “external Lithium-Ion batteries directly.” IEC 62368-1 applies to AV/ICT systems and components. It would not apply to an EPS within a larger system submitted for certification intended to charge generic Lithium-Ion batteries (e.g., 18650) for general applications, such as a system consisting of an EPS and battery cradle/charger for external batteries. While the EPS may be submitted for certification to an IEC 62368-based standard (which at the time of the submittal the intended system may be unknown), there are other IEC and UL standards (e.g., UL 1310, UL 1012) that would be used for such general Lithium-Ion battery charging applications.

For Annex M.4 of IEC 62368-1, it is applicable to those EPSs so designed for charging specific Lithium-Ion batteries used together with specific AV/ICT equipment and that can be evaluated (tested) as a system.

As this forum is not intended to analyze and provide guidance on specific designs, we suggest that you contact the UL Solutions office you work with and send in a request for an engineering engagement if you have a specific design or construction that you would like to discuss.

Annex M Equipment containing batteries and their protection circuits

How to determine compliance with the latest flammability requirements in UL 62368-1 for secondary lithium batteries?

More specifically, you asked (edited for clarity): Can you advise if batteries under the new version of UL 62368-1 are required to have a UL 94 V-2 or higher flammability rating to comply with the latest regulations for the NA market? Also, are legacy compliant end product systems required to have a metal housing to comply with the LVD / IEC / UL changes when the battery has a rating of UL 94 HB? It would be helpful if a document was released to share with installers. Also, as the January 2024 deadline approaches, will there be audits (recertification) required to determine compliance with the latest requirements, or in doubt, is it best to use of a flame-retardant batteries with a UL 94 V-2 rating or higher to ensure it meets the regulations?

In response, both the battery and product details in your question are not descriptive enough to be able to provide a precise response. However, we will assume that the batteries being asked about are secondary (rechargeable) lithium batteries used in Class III AV/ICT equipment.

First, let’s clarify, the effective date of UL 62368-1 Edition 3 (based on IEC 62368-1:2018) has been postponed to July 6, 2024 (18 months after the originally announced date - January 6, 2023, not January 2024). Detailed information related to the UL 62368-1 Effective Date is available via UL.com.

Related to fire enclosures for secondary lithium batteries, per Annex M.4.3 in UL IEC 62368-1 Edition 3, secondary lithium batteries should be provided with a fire enclosure according to Clause 6.4.8, which may be that of the secondary lithium battery itself, or of the cell, or a combination of cells, or may be that of the equipment containing the secondary lithium battery.

Note, the latest version of the standard, IEC 62368-1:2023 (Ed 4), has more details in Annex M.4.3 on battery fire enclosures. More specifically, the fire enclosure, in the case where it is part of the battery itself, should either comply with Annex S.1 (flammability testing on the battery), or be made of V-1 class material (via preselection), or be made of non-combustible materials (e.g., metal). In the case where the fire enclosure is established by the end product enclosure, the cells are considered a resistive PIS and the material of the fire enclosure should comply with Clause 6.4.8, which may result in a higher flammable class V-0 for combustible materials if the spacing from the resistive PIS is less than 5 mm. However, there remains an exemption from the fire enclosure requirement for secondary lithium batteries if the cell or a combination of cells comply with PS1.

Since you mentioned V-2 material, we would like to make special note that batteries using combustible materials with a V-2 class casing generally are not acceptable when a fire enclosure is required for secondary lithium batteries. Typically, a material of V-1 class or better would be required (per 6.4.8).

As battery fire enclosure requirements in UL IEC 62368-1 can be complex, and there appears to be a specific, detailed construction that needs review / analysis, we encourage you to contact UL Solutions for an in-depth engineering consultation.

Annex M Equipment containing batteries and their protection circuits

Annex M.2 of IEC 62368-1:2014 requires batteries and cells to comply with the relevant IEC standard, such as IEC 62133: 2013. If a battery and/or cell complies with IEC 62133-1:2017 or IEC 62133-2:2017, does it also need to comply with IEC 62133:2013?

Some years ago, IEC TC21/SC21A decided to split IEC 62133 into two standards while also incorporating a number of improvements. In 2017, IEC 62133:2013 was replaced by IEC 62133‐1:2017 for alkaline or other non‐acid batteries and IEC 62133‐2:2017 for lithium batteries. However, although IEC 62133-1 and IEC 62133-2 are the current standards for such chemistries, there is also the need for a transition period.

Please note that you reference IEC 62368-1:2014, Ed. 2, but IEC 62368-1:2018, Ed. 3, is also available now. IEC 62133, IEC 62133-1 and IEC 62133-2 are all listed in Annex M.2 of IEC 62368-1:2018 to allow for the transition.

If an AV/ICT product with a battery covered by the IEC 62133-x series is submitted for UL certification to IEC 62368-1:2014, a valid certification to IEC 62133-1 or IEC 62133-2 would be accepted for batteries and cells without also being compliant with the legacy IEC 62133:2013.

Annex M Equipment containing batteries and their protection circuits

I am trying to understand the highest and lowest specified charging temperature in Annex M.4.2 - can we regard the "charging operation temperature" in the battery specification something like 0-45 degree C as the two temperatures?

The “charging operation temperature” is often used to identify the highest and lower charging temperature for secondary batteries. When an end product manufacturer uses this to specify a range beyond to what identified for the component batteries (cells and/or packs) it is very important that they collaborate with the battery supplies to ensure the batteries will perform within the expanded temperature range and the expanded range will not result in overcurrent or overvoltage conditions that will result in failures in constructions that may result in risk of fire, explosion and/or leakage of materials. End product manufactures should continue their practice of working with their battery suppliers to make sure the batteries are tested at the component level for the needs of the end product.

In IEC 62368-1:2018, IEC 62133-2, Secondary cells and batteries containing alkaline or other non-acid electrolytes - Safety requirements for portable sealed secondary cells, and for batteries made from them, for use in portable applications - Part 2 Lithium systems, similar to IEC 62133:2012, Annex A, provides more detailed explanations of the effects of overvoltages along with temperatures and charging current. It explains that charging voltage and charging current need to be adjusted based on the temperature ranges. If the reader has not had an opportunity to review this Standard, it is recommended they do so.

Annex M Equipment containing batteries and their protection circuits

Per M.4.3, a fire enclosure is required for secondary lithium batteries. In the case the equipment enclosure does not meet the criteria of 6.4.8, such as being rated HB, can a fire barrier fulfill the intent of the requirement?

More specifically, you asked (edited for clarity): Annex M of 62368 states, "Secondary lithium batteries shall be provided with a fire enclosure according to 6.4.8. The fire enclosure may be that of the secondary lithium battery itself, of the cell or of a combination of cells or that of the equipment containing the secondary lithium battery. Equipment with batteries are exempt from the above requirement if the equipment uses a cell that complies with PS1." My question is, if the battery pack does not meet the criteria set out in 6.4.8 with regards to material flammability rating and the battery is considered a restive PIS, can a fire barrier be used between it and overall enclosure of the product and be in compliance? The battery would be less than 5mm distance from an enclosure using HB rated material. So basically, no overall fire enclosure either around the battery or the overall product. Seems to me the answer is "no" since annex M does not state anything about fire barriers.

We agree. The answer to your question is No, i.e., the scenario you describe, with an HB Enclosure (casing) combined with a Fire Barrier, does not meet the intent of M.4.3. However, we suggest you contact UL Solutions to discuss a specific construction in greater detail since not all battery and battery pack constructions are exactly the same, and compliance can depend on the details associated with a specific construction.

In the meantime, let's think of the difference between fire enclosure and fire barrier. The definition of fire enclosure is given in Sub-clause 3.3.2.3, which is to prevent fire spread from within the enclosure to outside the enclosure. Although the term "fire barrier" is not defined in Clause 3, it can be implied from 6.4.7.3 and other relevant subclauses that a fire barrier is to prevent fire spread from a PIS to a specific combustible material located in proximity to the PIS. In this context, the fire barrier is most likely to block fire propagation to one direction, but not necessarily in all directions. Thus, a fire barrier might not prevent the spread of fire from within the equipment (preventing fire spread in all directions) by surrounding the PIS and cell operating above PS1 with a fire enclosure. For this particular secondary lithium battery fire enclosure context, the purpose of the Fire Enclosure would be to prevent fire from a lithium battery and protection components from spreading outside the battery or equipment, instead of preventing fire spread to a specific direction toward specific combustible material(s) only.

Annex M Equipment containing batteries and their protection circuits

Are there any lithium battery specification limitation requirements, such as max voltage, width/height/length, etc., that one needs to consider for a wearable device for indoor/outdoor locations?

Battery-powered wearable electronics/devices are covered under the scope of IEC 62368-1:2018 (Ed. 3). If wearable devices are certified to IEC 62368-1, the type of aspects asked about (except design-specific width/height/length of batteries, which are not controlled, except by industry specifications for consumer-grade batteries) are covered under IEC 62368-1’s Annex M, Equipment containing batteries and their protection circuits.

Some of the important parameters considered/defined under Annex M include:

• 3.3.17.4 Highest Specified Charging Temperature Highest temperature specified by the manufacturer at a site on each individual cell comprising the battery during charging of a secondary battery. Note1 to entry: It is usually assumed that the end-product manufacturer is responsible to specify the safety-sensitive temperature, voltage or current of the battery, based on the specifications provided by battery supplier.
• 3.3.17.5 Lowest Specified Charging Temperature Lowest temperature specified by the manufacturer at a site on each individual cell comprising the battery during charging of a secondary battery. Note 1 to entry: It is usually assumed that the end-product manufacturer is responsible to specify the safety sensitive temperature, voltage or current of the battery, based on the specifications provided by battery supplier.
• 3.3.17.6 Maximum Specified Charging Current Highest charging current specified by the manufacturer during charging of a secondary battery.
• 3.3.17.7 Maximum Specified Charging Voltage Highest charging voltage specified by the manufacturer during charging of a secondary battery.

However, these parameters are to be specified by the device manufacturer, usually in collaboration with the battery and charger manufacturer and battery specifications.

Note Annex M has undergone considerable refinement in Edition 4 of IEC 62368-1, which was issued in May 2023.

UL Solutions has subject matter experts well versed in IEC 62368-1, including Annex M. As the complete answer to this topic is complex, and there appears to be a specific, detailed construction that needs review/analysis, you are encouraged to contact UL Solutions for an in-depth consultation via https://www.ul.com/services/iec-62368-1-testing-certification.

Annex N Electrochemical potentials (V)

What is the origin of Annex N of IEC 62368-1 (Annex J of IEC 60950-1), in particular the table of Electrochemical potentials (V)?

This question surfaces periodically. Unfortunately, it is not possible to provide as precise an answer as some may hope for.

However, the content of the table is based on basic galvanic corrosion science. It is our understanding it was proposed (with technical rationale) and accepted by IEC TC74 (predecessor to IEC TC108) many (30+) years ago based on an EDP/IT equipment manufacturer’s internal (desk) standard in use at the time. In the long history of EDP/IT/ICT equipment covered by IEC 435, IEC 950, IEC 60950-1, and IEC 62368-1, this sort of origin of a requirement is not uncommon.

We note, via a keyword search for “galvanic corrosion,” or similar, there are numerous forms and structures of the same or similar information found online, including several examples below.

https://structx.com/Material_Properties_001.html

https://www.jpcfrance.eu/technical-informations/raw-materials/corrosion-resistance/

https://blog.samtec.com/post/dissimilar-metals-in-mating-connectors/

If a manufacturer within the present AV/ICT Industry disagrees with the current content of Annex N, or believes it could be modernized, a method to address the concern would be to propose, with supporting technical rationale, to IEC TC108 via your National Committee.

Annex Q Circuits intended for interconnection with building wiring

For a Limited Power Source (LPS) determination per Annex Q, may a fuse be factored into compliance of an inherently limited power source, including Table Q.1, instead of the requirements for a non-inherently limited power source, including Table Q.2?

More specifically, you asked (edited for clarity): Asking how to correctly assess a combination of overcurrent device (certified fuse) and regulating network (non-certified DC/DC converter) for compliance with Annex Q? Should this be considered under Q.1.1 d), with additional compliance required per Table Q.2? (Need to measure maximum current and power with fuse bypassed.) Or, alternatively, should this construction be considered under Q.1.1 c), with additional compliance required per Table Q.1, both with and without a single fault in the regulating network? Or, is there another option?

In response, the intent of the requirements in Clause Q.1, Limited Power Source (LPS), of Annex Q, Circuits intended for interconnection with building wiring, is to be able to classify a power source needing to be defined as LPS as either inherently limited (without a fuse) or non-inherently limited (requiring use of a fuse), without mixing methods.

In other words, if the output of the DC-DC converter (certified or not) without a fuse added is inherently limited per either Q.1.1a), without a regulating network, or Q.1.1b), with linear or non-linear impedance, or Q.1.1c), with a regulating network, including application of Table Q.1, then the DC-DC converter has an inherently limited LPS output.

However, if the DC-DC converter (without fuse) does not comply with Q.1.1a), b) or c), including Table Q.1, then adding a fuse (typically not to exceed 5A) and applying Q.1.1d) is the remaining option to comply with LPS, unless an IC Current Limiter (instead of fuse) is added per Q.1.1e) and Clause G.9.

The intent of the standard is that a fuse is not to be factored into application of the requirements for inherently limited power sources per Q.1.1a), b) or c).

Note, the application Clause Q.1 of Annex Q is similar to application of Class 2 requirements in the U.S. (per the National Electrical Code (NEC), Article 725, and UL 1310, Class 2 Power Units) since the LPS requirements in IEC 62368-1 (originally IEC 60950-1) have NEC Class 2 as their origin.

As this forum is not intended to analyze and provide guidance on specific designs, we recommend that you contact UL Solutions and request an in-depth consultation if you have a specific design or construction that you would like to discuss.

Annex S Tests for resistance to heat and fire

When performing the needle flame test in Annex S.1, if the burning material extinguishes before the first 30 seconds, is this an acceptable result?

More specifically you asked: When performing the needle flame test in Annex S.1, the standard states the test flame is applied for 10 seconds and, if the flame does not exceed 30 seconds, the test flame is re-applied. However, if there is no self-sustaining flame for the full 30 seconds, is this an acceptable result (test passed)?

The needle flame test of S.1 is derived from IEC 60695-11-5 with some modifications for 62368-1, such as flame application time and compliance.

The application of the test flame is required to follow the stated sequence (it is one sequence, not separate tests):

• the test flame is applied for 10 s;
• if flaming does not exceed 30 s, the test flame is immediately reapplied for 1 min at the same point;
• if again flaming does not exceed 30 s, the test flame is immediately reapplied for 2 min at the same point.

The compliance criteria require all of the following:

• after every application of the test flame, the test specimen shall not be consumed completely; and
• after any application of the test flame, any self-sustaining flame shall extinguish within 30 s; and
• no burning of the specified layer or wrapping tissue shall occur.

As mentioned in the compliance criteria, each application of flame is required to meet all three dashes.

Specifically, to the submitted question, the 2nd and 3rd dashes (of the first set of dashes above) require the test flame to be applied to the same test specimen if no flame remains after the first 30-sec application and there is no burning of wrapping tissue after 1st application. Therefore, it is not an acceptable result alone for the complete test if the test specimen’s sustaining flame extinguishes within the first 30 seconds - that is required to pass part of the test, but then there are two other dashes that also need to be applied and met.

Furthermore, S.1 requests three test specimens - even if the first specimen complies, the remaining two specimens also are required to meet the above tests as well. All three specimens are required to pass the test.

Annex Y Construction requirements for outdoor enclosures

What tests are required for the gaskets used in AV/ICT equipment outdoor enclosures investigated to UL 62368-1, 3rd Edition?

More specifically, you asked (edited for clarity): The Standard includes requirements for outdoor enclosures. However, the test requirements for the gaskets are unclear. The three gasket tests (tensile strength, elongation, and compression) do not clearly specify the applicable types of gaskets. If an O-ring is used, which tests are required?

In response, UL 62368-1 3rd Edition provides requirements for outdoor enclosure construction in Annex Y. The gaskets requirements are stated in Clause Y.4. The four common types of gaskets found in AV/ICT products are solid gaskets (including O-ring types), closed cell types, and open cell types.

The tensile and elongation tests stated in Clause Y.4.3 are required for all types of gaskets that can stretch, including O-ring gaskets.

The compression test stated in Clause Y.4.4 is required for gaskets with closed cell construction, such as O-rings subjected to repeated mechanical stress via opening and closing of a door. Therefore, if the mentioned O-ring gasket is made of closed cell construction and subjected to repeated mechanical stress, the compression test is required.

It should also be noted that gaskets that are subjected to oil or coolant are required to be oil resistant per Clause Y.4.5. If the gaskets are secured with adhesive or by mechanical means, the construction also is required to be evaluated per Clause Y.4.6.

As this forum is not intended to analyze and provide guidance on specific designs, we recommend that you contact UL Solutions and request an in-depth consultation if you have a specific design or construction that you would like to discuss.

Annex Y Construction requirements for outdoor enclosures

How to address challenges complying with the Y.4.3 tensile strength and elongation tests for gaskets?

More specifically you asked (edited for clarity): IEC 62368-1 Annex Y defines construction requirements for outdoor enclosures. The ongoing problem we have is that gaskets meeting the test requirement of Y.4.3 are virtually non-existent and the actual gasket samples can be difficult to impossible to test due to dimensions. Additionally, Y.4.3 states, regarding the test, “As an alternative, the tensile strength and elongation tests as given in ISO 37, ISO 1798, ASTN D412 or ASTM D3574 may be used.” Is this saying that a gasket which simply has an ASTM D412 test specification can be accepted in place of the heat aging test of Y.4.3? For the above-mentioned difficulties that make it impossible to test due to dimensions, is there any activity in the standards committee to address this requirement? I will point out that even equipment designed for Hazardous Locations and Explosive Environments does not have such a challenging requirement. I also point out that there is a much more common standard for elastomeric materials (than UL 50E), which is UL 746C, where an f1 rating ensures 50% tensile strength and 50% elongation remaining after 168 h in 70 °C water immersion, which compares reasonably closely to the clause Y.4.3 requirement of 75% tensile strength and 60% elongation remaining after 168 h in 70 °C circulating air. It would be very helpful if UL 746C f1 was also acceptable alongside UL 50E under the sub-clause Y.4.1 national deviation.

In response to your question about the difficulty in performing the tests, as this forum is not intended to analyze and provide guidance on specific designs or tests for specific applications, we suggest that you contact the UL Solutions office you work with and request an engineering consult if you have a specific design or test that you would like to discuss.

For the gasket tests, it was asked, what was the intent of the inclusion of the sub-clause Y.4.3 alternative standards for the tensile strength and elongation tests? We confirm that these alternative standards only are referred to for the test method – the conditioning requirement (samples subjected to a temperature of 69 °C to 70 °C in circulating air for 168 h) and the compliance criteria (tensile strength of not less than 75 % and an elongation of not less than 60 % of values determined for unaged samples) still need to be followed as per Y.4.3. The intent of referencing these alternative standards is to allow for alternative test samples and the test setup. Also, while existing practice has permitted the test samples for Y.4.3 to be an actual end product sample gasket (although often there are test challenges due to actual gasket size and composition), conducting the testing on sample materials (not the gasket itself), often is a more realistic approach. Also, the test samples for the alternative standards should be prepared per the criteria in them, such as by punching (via dies), cutting, moulding, or other appropriate methods. Please see the details in the alternative standards referenced.

Regarding your question about related activity of the involved standards committees, we confirm there is nothing currently being worked on related to this topic within IEC TC108, which has responsibility for IEC 62368-1. However, if you believe you have insight or a sound proposal for improving the standard, we encourage you to be proactive and make a proposal (with technical rationale) to improve IEC 62368-1 via your National Committee that participates on IEC TC108.

Related to the National Difference for USA and Canada that was mentioned, Y.4DV DC of CSA UL 62368-1 Ed. 3 allows use of, as an alternative, gasket materials tested in accordance with UL 157, or the gasket tests in CSA C22.2 No. 94.2 / UL 50E. For more information about associated certifications, please refer to the UL Solutions categories (CCNs) JMST2 and JMLU2 in the UL Solutions Product iQ. However, suitable gaskets complying with these standards only would be acceptable for Canada and the U.S. and not under the IECEE CB Scheme.

Related to your preference for UL 746C, we note that UL 746C does not cover gaskets explicitly under its scope. If you believe an alternative method for considering gaskets per test protocols in UL 746C should be included in CSA UL 62368-1, we suggest that you should consider making a proposal (with technical rationale) via the UL Standards & Engagement Collaborative Standards Development System (CSDS).

Annex Y Construction requirements for outdoor enclosures

For gaskets used to seal a component to prevent water entry in an outdoor enclosure, does Annex Y require a UV radiation test on the gasket in addition to regular gasket tests?

More specifically asked: For outdoor enclosures, non-metallic parts require compliance with UV radiation requirements in Annex Y.2. If a gasket is used to seal a component to prevent water entry, does it require a gasket UV radiation test per Y.2 in addition to gasket tests per Y.4, or does it only require normal gasket tests per Y.4?

All references are to IEC 62368-1:2018, in which IEC 60950-22 (Outdoor ITE) content has been incorporated into Annex Y (Construction requirements for outdoor enclosures) and other parts of the Standard.

UV radiation testing per Y.2 normally is not required on gaskets in addition to normal gasket testing per Y.4.

UV radiation testing is required for polymeric materials exposed to radiation such as sunshine. When polymeric materials are exposed to UV radiation for a long time, materials can become embrittled. As a result, safeguards, such as electrical enclosures, can be defeated over time, and ordinary persons could be exposed to hazardous energy sources.

In general, gaskets are enclosed between enclosures along a joint rather than directly being fully exposed to UV radiation. Therefore, it is the view of IEC TC108 and 62368-1 that such constructions do not require a UV radiation test, only general gasket tests in accordance with Annex Y.4.

This guidance is consistent with the IEC TC108 Interpretation Panel Question Q01 (published as 108/642A/INF), which has the same opinion for cable gland (gasket) evaluated to IEC 60950-22. A gland (gasket) does not require UV testing since the UV radiation will not penetrate into the whole gland/gasket.

Annex Y Construction requirements for outdoor enclosures

Do UL Solutions’ approved gaskets certified per UL 157 still need to be subjected to gasket tests per Annex Y.4.3 and Y.4.4 of UL 62368-1, Ed. 3?

More specifically you asked: Annex Y.4 lists specific tests for gasket materials, in particular Y.4.3 and Y.4.4 for gaskets employed in an outdoor enclosure subjected to water or dust. Are these tests required for UL Solutions listed gaskets? UL157 contains similar, but not identical requirements - e.g., min. tensile strength requirement in UL157 is 60%, not 75%, but the oven aging is more severe.

In response, it is noted that a National Difference for USA and Canada, Y.4DV DC of UL62368-1 Ed. 3, allows use, as an alternative, gasket materials tested in accordance with UL 157, or the gasket tests in CSA C22.2 No. 94.2 / UL 50E. For other countries, these gasket materials may be accepted at the discretion of Recognizing NCB. As indicated in sub-clause 4.1.7, whenever standard provides choice between different criteria of compliance, it is left to the manufacturer to decide which shall be used.

Annex DVA Canadian and U.S. regulatory-based requirements

Does a Class II cord-connected product investigated to UL 62368-1 and that is intended to be supplied by standard 15A or 20A outlet need to employ a polarized-type attachment plug?

More specifically, you asked (edited for clarity): Is a polarized plug mandatory for a paper shredder based on UL 62368-1? I found it’s a requirement in UL 60335 or UL 60950, but it’s not stated in UL 62368-1.

In response, UL 62368-1, Annex DVA (Clause G.4.2), stipulates that a Class II product that employs a single pole disconnect device is to be provided with a polarized plug-type attachment plug. This requirement is a national difference from IEC 62368-1 and is driven by the National Electrical Code (NEC). It is the same requirement that was in UL 60950-1. So, polarization is not required for all Class II constructions.

As this forum is not intended to analyze and provide guidance on specific designs, we recommend that you contact UL Solutions and request an in-depth consultation if you have a specific design or construction that you would like to discuss.

Annex DVH Permanently connected equipment – mains connections

Is an AV/ICT product employing a terminal block for AC mains permanent connection without a wiring compartment eligible for the UL Listing Mark?

More specifically you asked (edited for clarity): We design a switch product that has a permanently connected terminal block with three terminals: Line, Neutral and Protective Earth. The switch is rated 100-240 Vac. If we plan to have the switch evaluated as a complete unit (UL Listing Mark) for connection to AC mains, the user manual defines the proper installation, including installation of our product in a suitable Listed cabinet. The wiring compartment is not provided by us. Can this construction be UL Listed?

In response, in order for an AV/ICT product intended for permanent connection to an AC Mains to be considered eligible for applying a UL Listing Mark, all related requirements in CSA UL 62368-1 are to be met, including Annex DVH, Permanently connected equipment – mains connections, which generally requires that the wiring compartment shall be provided. (There is an exception for equipment connected to DC Mains and installed in a Restricted Access Area.) If the wiring compartment is not provided, the product can be considered eligible for the UL Recognition Mark as it would rely on an end product to satisfy the permanent connection safeguard requirements of Annex DVH and Annex G.7.6, Supply wiring space.

As this forum is not intended to analyze and provide guidance on specific designs, we recommend that you contact UL Solutions and request an in-depth consultation if you have a specific design or construction that you would like to discuss.

Annex DVH Permanently connected equipment – mains connections

For UL 62368-1 certification, if a PE symbol (per IEC 60417-5019) is marked next to the protective earthing terminal of a terminal block used for a permanent connection, does the PE terminal screw or nut additionally need to be green in color?

More specifically you asked (edited for clarity): We design networking routers meeting UL 62368-1. We have a permanently connected equipment (supply type) using a terminal block which has three terminals Line, Neutral and Protective Earth. The supply is DC MAINS. The protective EARTH or ground terminal is marked with PE Symbol as per IEC 60417. If this symbol is there, do we also need a green color nut or screw? (This PE terminal is covered by a cover, so is not visible and only the PE mark per IEC 60417 can be seen.)

In response, the protective earth terminal screw or nut does not need to be additionally green in color if the IEC 60417-5019 symbol is provided next to the PE terminal. The IEC 60417-5019 PE symbol marking next to the earthing terminal is sufficient to indicate that the terminal is intended for the protective earthing conductor.

In UL 62368-1, these considerations, including use of green color for PE, are based on the requirements in the National Electrical Code (NEC). For details, and additional considerations on visibility, please see Annex DVH (normative) – Permanently connected equipment – mains connections, and its requirements in DVH.5.1, Identification of protective earthing terminal, which states, “If the terminal is not visible, the conductor entrance hole shall be marked with the word “green” or “ground,” the letters “G” or “GR,” or the grounding symbol (IEC 60417, No. 5019), or otherwise identified by a distinctive green colour.” Therefore, the described construction appears to meet the intent of this NEC-driven requirement in UL 62368-1.

As this forum is not intended to analyze and provide guidance on specific designs, we recommend that you contact UL Solutions and request an in-depth consultation if you have a specific design or construction that you would like to discuss.