Wiring sizing for control panels.

[binney]

I've made a change in jobs and have been faced with doing some work in control panels. Where can I find info on how to size the wiring? Or find the exceptions that pertain to it. We're using all MTW wire.

 

[Ingenieur]

When I built them for the power ckts (vfd's, starters, etc) I used the NEC for a basis of dsign although I believe it may not completely apply

for the actual control wiring UL 508
in these ckts current is usually low <10 A so 14's are usually the std

1. The basic requirements for Industrial Control Panels rated not more than 600 volts and for installation in ordinary locations are specified in UL 508A, the Standard for Safety of Industrial Control Panels.

 

[Saturn_Europa]

I'd use article 240.4 of the NEC. For true control work in PLC cabinets I usually only see 16 gauge wire. NEC regulates continuous load on 16 gauge copper wire to 8 amps which is plenty. Be sure to read the stipulations.

 

[Jraef]

Years ago UL508A and the NEC didn't always agree on wire sizes, they fixed that. The only difference now is that the rules for using wire sizes below 14ga are a little less stringent in UL508A than they are in the NEC, but most people I know will just stick to 14ga minimum anyway.

 

[Smart $]

And there is also NFPA 79: Electrical Standard for Industrial Machinery.

http://www.nfpa.org/codes-and-stand...list-of-codes-and-standards?mode=code&code=79