UL508A on Standoff Insulators

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12 Insulating Barriers

12.1 When an insulating material is used as a barrier in order to comply with the required over surface or

through air spacings, or both, the required spacings in Section 10, Spacings, shall be applied by tracing

over the surface of the insulator and through air to the edges of the insulator.

12.2 Insulating material used as specified in 12.1 shall comply with the following requirements:

a) The material shall be:

1) An insulating material described in Table 12.1; or

2) Tubing or sleeving complying with 29.2.3 and rated for the voltage involved;

b) The material is able to be in direct contact with uninsulated live parts; and

c) The material does not serve to physically support or maintain the position of an uninsulated live part.

Exception: A material that does not comply with 12.2 shall be investigated as an insulating barrier in

accordance with the requirements in the Standard for Industrial Control Equipment, UL 508.

13 Insulating Materials

13.1 An insulating material that is used for the direct support of an uninsulated live part, such as a standoff or insulating base for a bus bar, current shunt, or terminal, shall comply with 13.2. A material is in direct support of an uninsulated live part when:

a) It is in direct physical contact with the uninsulated live part; and

b) It serves to physically support or maintain the relative position of the uninsulated live part.

Exception: A material in direct contact only with uninsulated live parts of a low-voltage limited energy circuit or a Class 2 circuit is not required to comply with 13.1.

13.2 Insulating material used as specified in 13.1 shall comply with the following requirements:

a) The material shall be an insulating material described in Table 13.1; and

b) The dimensions of the insulating material shall comply with the required spacings of Section 10, Spacings.

Exception: A material that does not comply with 13.2 shall be investigated as an insulating material in

accordance with the requirements in the Standard for Industrial Control Equipment, UL 508.

13.2 Recognized Standoffs UL 67, UL 891 QEUY2 Any insulating standoff that complies with 13.2(b)

13.2 Exception Other insulating materials UL 508 – Construction described in Procedure SA3.3 Polymeric (plastic) mechanical parts that serve to:

a) Physically support live parts, such as a standoff for a bus bar, shall comply with Section 13, Insulating Materials.

b) Provide insulation of live parts in lieu of electrical spacings, such as insulating barriers or tubings, shall comply with Section 12, Insulating Barriers, or 29.2.3.

c) Provide a mechanical intrusion barrier are not required to be Listed, Recognized, or Procedure described.

29.3.9 A bus bar shall be supported by insulators that comply with Section 13, Insulating Materials, and

that are rated 90°C (194°F) minimum.