UL508A Motor connections with cable 16 AWG

[tv002700]

I am working on a customer's panel that has a number of field connections for small motors (max 1/2 HP). They have requested to connect the motors using 16AWG 4c cable with the following ratings/approvals:

600V UL TC
1000V UL AWM
UL Type TC ER
UL Type MTW or DP-1
Class 1, Div 2 per NEC art. 336, 392, 501

I am evaluating this panel for compliance with UL508A and have identified the following possible issues:

1. Section 28.3.1 states a minimum size of 14AWG for field wiring power conductors. I have found NEC exceptions that allow 16AWG for connection to motors protected by 30A max class CC fuses (which i have). However, i cannot find a similar exception in the UL508A spec.
2. Section 28.5.4

The cord shall comply with the Standard for Flexible Cord and Fixture Wire, UL 62, and be one of​

the following types: S, SE, SEO, SEOO, SJ, SJE, SJEO, SJEOO, SJO, SJOO, SJT, SJTO, SJTOO, SO,​

SOO, ST, STO, STOO, or portable power cable type G, PPE, or W power cable.

The requested cable does not comply with this section. However, the cable is type MTW which complies with section 29.2.1 for internal wiring of power circuits.​

Can anyone offer some insight here? I know it is fairly common practice to connect motors using this type of cable but i can't seem to match it up with the spec. Do the cables connecting between my panel and the motors fall outside the UL508A Industrial Control Panel scope? I have provided terminals sized for 14 AWG and all internal wiring for the motors is 14 AWG type MTW.

Thanks.

 

[Dennis Alwon]

Does 400.7 and 400.8 come into play. I don't know about the UL issues. Are these motors cord and plug or permanent wiring?

 

[petersonra]

I am working on a customer's panel that has a number of field connections for small motors (max 1/2 HP). They have requested to connect the motors using 16AWG 4c cable with the following ratings/approvals:

600V UL TC
1000V UL AWM
UL Type TC ER
UL Type MTW or DP-1
Class 1, Div 2 per NEC art. 336, 392, 501

I am evaluating this panel for compliance with UL508A and have identified the following possible issues:

1. Section 28.3.1 states a minimum size of 14AWG for field wiring power conductors. I have found NEC exceptions that allow 16AWG for connection to motors protected by 30A max class CC fuses (which i have). However, i cannot find a similar exception in the UL508A spec.
2. Section 28.5.4

The cord shall comply with the Standard for Flexible Cord and Fixture Wire, UL 62, and be one of​

the following types: S, SE, SEO, SEOO, SJ, SJE, SJEO, SJEOO, SJO, SJOO, SJT, SJTO, SJTOO, SO,​

SOO, ST, STO, STOO, or portable power cable type G, PPE, or W power cable.

The requested cable does not comply with this section. However, the cable is type MTW which complies with section 29.2.1 for internal wiring of power circuits.​

Can anyone offer some insight here? I know it is fairly common practice to connect motors using this type of cable but i can't seem to match it up with the spec. Do the cables connecting between my panel and the motors fall outside the UL508A Industrial Control Panel scope? I have provided terminals sized for 14 AWG and all internal wiring for the motors is 14 AWG type MTW.

Thanks.

UL508a does not cover field wiring (wiring outside of the ICP). The sections you mentioned refer to wiring inside the ICP.

 

[Jraef]

UL508a does not cover field wiring (wiring outside of the ICP). The sections you mentioned refer to wiring inside the ICP.

Well, Section 28 in general does have to do with the Field wiring TERMINALS, but not the wire itself. They are just saying that for a UL508A listed panel, you cannot use terminals that will only accept wires SMALLER than #14. But most pressure connection type terminals handle a RANGE of wire sizes. So for example if you use a terminal that accepts #22 - #16, you cannot UL list that panel. If you use one that handles #22-#14, that's fine. The reason is, UL has no idea if the special conditions allowing for wire smaller than #14 might apply of not, so they require that any field wiring terminal WILL allow #14 if necessary.

What the user connects to it in the field is between them, their AHJ and their conscience.

28.5 only applies IF it is portable equipment, not intended to be connected through conduit.