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Appendix A

The following is a brief summary of the fourth edition of UL 746C, the Standard for Safety of Polymeric Materials -- Use in Electrical Equipment Evaluations, which was effective as of June 1, 2004, and the action that may be required to determine compliance.

Figure 2.1

Revised figure, which is a guide for polymeric evaluations.

3.3.1, 3.19.1, 3.19.2, 3.21.1, 3.21.2

Definitions have been revised or added for clarification.

No formal response with regard to these requirements is necessary when compiling your Lists C and D.

4.1, 4.2

These are general guideline requirements. There is a direct reference to Table 4.1, which contains new requirements. See comments under Table 4.1 for comments and requested information.


This paragraph has been revised to address the use of metal sub-enclosures and, if employed, specifies the flammability classes allowed for the overall outer enclosure. The exception allows a V-0 material to be substituted for the metal sub-enclosure for portable equipment described in Path II of Table 4.1.

In compiling your response to this letter under Lists C and D, you should indicate if a metal or V-O sub-enclosure is used to house all insulated or non-insulated live parts in circuitry that involves a risk of fire as defined by paragraph 3.30 of UL 746C.

4.4, 4.5

These are relocated new/revised paragraphs that were originally in the previous edition of UL 746C and therefore these requirements have already been applied to current Listings.

Table 4.1

Table 4.1 has been revised and consolidates the requirements for all types of equipment [Path I: portable attended household equipment, Path II: all other portable equipment (see footnote "k" of Table 4.1), and Path III: all other equipment] under one table. Path II of the table has been revised to require a minimum V-rated enclosure material for portable equipment, which includes portable unattended household, attended and unattended commercial equipment. An HB enclosure may be used in portable unattended household equipment provided that the equipment complies with the criteria specified in section 4A. (See comments under section 4A below.)

Flow charts at the following Web address can be used as a guide when evaluating equipment to determine compliance with the applicable requirements for portable equipment.

When compiling Lists C and D, indicate for all portable equipment the flammability class for each enclosure material employed. If the enclosure material is rated HB, indicate if the enclosure was previously subjected to the end-product flammability test as described in section 17 and 18 of UL 746C and provide the report date and test record number.

Only portable unattended household equipment can be evaluated in accordance with the requirements outlined in the new section 4A, "portable unattended household equipment -- alternate path." See exception to footnote "b."

Section 4A

This new section outlines requirements only for portable unattended household equipment employing HB-rated enclosure materials. A review and evaluation of all electrical connections and all components (materials, wiring, tubing, sleeving and tape) adjacent to electrical connections will be required.

When compiling Lists C and D, indicate for each product all components and the types of connections employed in the equipment. For each component, specify the catalog or type number, manufacturer, UL category and CCN, and the manufacturers' grade, type designation, and flammability rating of the component material.

For example: The connector in the primary line circuit is catalog no. 123 manufactured by XYZ Inc. The category for the device is wire connectors and soldering lugs, (ZMVV), covered under File E12345. The material of the device is manufactured by Plastic Inc., grade ABC, rated V0. The flammability classification marking (V0) will be identified on each component device as required by paragraph 4A.2.2.

If a plastic material is in contact or within 3 mm of an electrical connection, provide the manufacturer, grade and type designation of the material. If wire, tubing, sleeving or tape is located within 3 mm of an electrical connection, provide the manufacturers' name, catalog or type number, and the UL category.

Note that section 4A does not apply to components as specified under exception no. 3 of paragraph 4A.1.3. However, all electrical connections to these devices shall comply with sections 4A.2, 4A.3 and 4A.4.

8.1, 8.1.1-8.1.6, Table 8.2

Paragraphs detail general guidelines when evaluating material property considerations.


Paragraphs detail general guidelines when evaluation of materials does not meet pre-selection test performance levels. No review is necessary as these are editorial revisions.


These paragraphs have been revised and consolidated with the requirements in table 8.1. No review is necessary as these are editorial revisions.

Table A.1

Table A.1 was relocated from section 7. No review is necessary as these are editorial changes.

10.1, 14.3, 32.1, A.2

Editorial revisions.