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UL 746C FAQ

The following FAQ has been prepared to assist you in understanding the revised requirements in UL 746C which became effective June 1, 2004.

  • How will I be notified if my product is 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.

  • What products are affected?

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

  • What are the major changes to UL 746C?

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

  • Are there any exceptions or options?

    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.
  • How are component manufacturers affected?

    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.

  • How are plastic manufacturers affected?

    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.