Underwriters Laboratories

The large majority of UL's wire and cable Standards are intended to be compatible with the installation requirements of the National Electrical Code (NEC). Some exceptions are boat cable, marine shipboard cable, and appliance wiring material. UL staff devotes significant resources to the development of the NEC, which is published by the National Fire Protection Association (NFPA).

No. The UL E-number is a valid identifier for the organization responsible for a product but not an indication that the product is Listed, Classified, verified or Recognized. Only the appropriate UL Mark -- on the wire or cable or on its packaging -- is a valid indication of UL certification. UL assigns a unique E-number (E and a 3- to 6-digit number for wire and cable products) to each applicant in every product category. To find the responsible organization for a product when the E-number has been used for identification, go to UL's Online Certifications Directory, select "Search By UL File Number" and enter the E-number.

The ampacity of a wire or cable is the amount of current that the wire or cable can transmit without exceeding its rated temperature. An ampacity marking on a wire or cable or a reference to a specific ampacity for a wire or cable in a UL wire or cable standard is not feasible since ampacity varies according to the actual conditions under which the cable will operate. These conditions include the ambient temperature, installation environment (e.g., free-air), conduit or directly buried in the earth. The National Electrical Code provides two methods for the cable user to determine ampacity for a cable based on the installation conditions.

The term "verified," when used in a UL marking, means that the product has been tested and complies with one or more specific requirement. These requirements may be safety- or performance-related. In the UL system, the words "Classified" and "verified" mean the same thing. For a complete explanation of "Listed," "Classified" and "Recognized," read more on the UL Mark.

The guide information for most of UL's product categories provides valuable information regarding intended use and installation requirements. To view this information, go to UL's Online Certifications Directory. Use the keyword search to determine the links to files that are appropriate. Each file contains an additional link to the guide information.

The significance of the numbering systems is as follows:

For additional information, refer to the guide information for category AVLV2 -- Appliance Wiring Material.

The UL appliance wiring material style pages are currently being revised. References within the style pages are obsolete. Instead, refer to the guide information for AVLV2 -- Appliance Wiring Material.