Equipment Control Panel Wiring Protection

[jms53]

What are the NEC requirements for control wiring protection that does not leave the enclosure? Have 2 relays being controlled by individual switches found on panel door. Overcurrent and ground fault protection (20 Amp Breaker) for two motors are provided by breakers and internal motor thermals. Using #14 AWG to control definite purpose relays found in enclosure. Motors are fed with #12 AWG. Comments?

Thanks,

 

[paulengr]

It’s not that easy.

The panel can fall under 3 different Cides.

It might be UL 508A or 508. Or some other NRTL. Look for a sticker.

Or it might be an “NEC panel”. In that case treat like field wiring. Same rules apply as any other general wiring (chapters 1-4). General motor controls are article 430 or 440.

 

[tom baker]

If this is a motor controller, the rules are in 430.102. How you protect the wiring depends on if the control ckt is tapped, or is protected by a small fuse.
I always used a 5 amp fuse and 16 awg control wires, it’s just easier than using tapped ( from motor ckt) wires.
And if this is a UL 508A panel, then modifying the wiring can get into UL issues

 

[petersonra]

What are the NEC requirements for control wiring protection that does not leave the enclosure? Have 2 relays being controlled by individual switches found on panel door. Overcurrent and ground fault protection (20 Amp Breaker) for two motors are provided by breakers and internal motor thermals. Using #14 AWG to control definite purpose relays found in enclosure. Motors are fed with #12 AWG. Comments?

Thanks,

If this is wiring you are doing in the field it is just wires like any other wires. Protect them the way that you would protect any other class one control circuit wires. Article 725 maybe helpful to understand the actual requirements.

If it is a listed enclosure and the wiring is part of the factory assembly then I wouldn't worry about it at all. It is up to UL to decide what is appropriate.

 

[paulengr]

If this is wiring you are doing in the field it is just wires like any other wires. Protect them the way that you would protect any other class one control circuit wires. Article 725 maybe helpful to understand the actual requirements.

If it is a listed enclosure and the wiring is part of the factory assembly then I wouldn't worry about it at all. It is up to UL to decide what is appropriate.

This is clearly a motor control or general purpose wiring because it describes controlling motors. This falls under 430. 725 does not apply. See 725.3(F).

Plus honestly by the time you get to class I power limited circuits there is no longer any practical difference between this and chapter 1-3 wiring. So why use a section intended for telecom at all? For instance it’s common practice to leave spare conductors, or use one common tray cable that has extra conductors.. Under 725.25 these are “abandoned” and must be removed. No such requirement under chapter 3 methods.

In addition it would be obvious if it’s 725 because it SHOULD (725.30) be marked that way.

Just because there are those that believe that POE is going to be able to run a 250 HP motor starter doesn’t make it so.

 

[tom baker]

This is clearly a motor control or general purpose wiring because it describes controlling motors. This falls under 430. 725 does not apply. See 725.3(F).

Plus honestly by the time you get to class I power limited circuits there is no longer any practical difference between this and chapter 1-3 wiring. So why use a section intended for telecom at all? For instance it’s common practice to leave spare conductors, or use one common tray cable that has extra conductors.. Under 725.25 these are “abandoned” and must be removed. No such requirement under chapter 3 methods.

In addition it would be obvious if it’s 725 because it SHOULD (725.30) be marked that way.

Just because there are those that believe that POE is going to be able to run a 250 HP motor starter doesn’t make it so.

Art 725 will apply if the control circuit is not tapped and has a separate supply, often the separate supply is from a fuse in the motor controller


this fuse in the control circuit makes it fall under the rules in Art 725