Underwriters Laboratories

The Standards and categories that are affected are those that directly reference UL 746C in the end-product Standard. The requirements for all Standards impacted have been effective as of June 1, 2004. Click here for a list of the Standards and respective categories that are affected.

A letter was sent notifying manufacturers of products that have been affected. The letter summarized the changes in UL 746C and outlined the information needed in order to proceed with the review process.

The Standards and categories directly impacted include all portable unattended household equipment and portable commercial attended and unattended equipment.

For the products affected, the flammability level for the enclosure is now required to be a "V" (V0, V1, or V2) rated material.

There are some exceptions and options to choose from.

1. An HB-enclosure material may be employed if it complies with the end-product flammability test in accordance with sections 17 or 18 of UL 746C.
2. If a metal or V-0 sub-enclosure houses all insulated or non-insulated live parts that involve a risk of fire, then the overall polymeric outer enclosure may be classified HB. See paragraph 4.3 of UL 746C.
3. An HB-enclosure material may be employed in portable unattended household equipment provided that the equipment complies with the requirements in section 4A of UL 746C.

Some end-product manufacturers may choose to employ an HB enclosure material and will require a review of the materials supporting and within 3mm of each connection. Component manufacturers may need to comply with the requirements as outlined in section 5. Section 5 (portable unattended household equipment -- alternate path) of UL 746C outlines requirements for electrical connections. The "alternate path" requires that all electrical connections such as wire nuts, splicing wire connectors, quick-connect terminals, terminal connectors, multi-pin, and other forms of wire connectors shall comply with their respective component standards and employ materials rated V-0 or V-1. This means that the component manufacturer shall mark the flammability classification of the insulating material on the connector, smallest unit container, or on an information sheet placed in the smallest unit container. Other small-scale flammability classifications in accordance with paragraph 5.3.1 are also acceptable. A minimum glow-wire ignitability temperature (GWIT) and a glow-wire flammability temperature (GWFT) of 750 degrees C for the material are also acceptable.

Plastic manufacturers may need to work closely with both end-product manufacturers and component manufactures to choose the appropriate plastic material for their particular application. Since glow wire indices may be offered as an alternative design choice parameter for component manufactures, glow wire data on the plastics recognition card may be helpful in selecting the appropriate material.