When is conductor considered non-current carrying?

[electricus]

If it is a ground, or not a feeder or branch circuit?

Then are these the categories:

1. Feeders (current carrying)
2. Branch Circuits (current carrying)
3. Control Circuits (not current carrying?)
4. Ground (not current carrying)

To save space and materials if I have a 3/4" EMT with 8 current carrying branch (circuit) conducts and want to add 3 more control wires can I? I'm not exceeding my conductor current rating after derating and I'm not exceeding my conduit fill.

 

[K8MHZ]

Even if you are OK with the NEC, there may be some interference issues resulting from putting control wires in the same conduit as branch circuit wiring.

I try to avoid the practice whenever possible.

 

[raider1]

310.15(B)(2)(a) Exception#1 (2008 NEC) or 310.15(B)(3)(a) second paragraph (2011 NEC) allow you to omit control circuits from counting as current carrying conductors for the purposes of ampacity adjustment for more than 3 current carrying conductors in a raceway.

Chris

 

[electricus]

K8MHZ

Even if you are OK with the NEC, there may be some interference issues resulting from putting control wires in the same conduit as branch circuit wiring.

I try to avoid the practice whenever possible.​

Even when the branch circuit is 120/480vac and the control circuit is 120vac, you separate the 120vac branch circuit out?

raider1 310.15(B)(2)(a) Exception#1 (2008 NEC) or 310.15(B)(3)(a) second paragraph (2011 NEC) allow you to omit control circuits from counting as current carrying conductors for the purposes of ampacity adjustment for more than 3 current carrying conductors in a raceway

I did come across this later, and it also states in 725.51 that they don't need to be counted if the current is less than 10% of the rating of the conductor.

 

[K8MHZ]

Even when the branch circuit is 120/480vac and the control circuit is 120vac, you separate the 120vac branch circuit out?

As a design issue, yes. It's much easier to troubleshoot problems if they are kept separate, even if interference may not be a problem itself.

If all you care about is Code minimum, that's a different story. I do a considerable amount of troubleshooting so I may have a different perspective than you have, if all you are concerned with is the initial installation.

 

[don_resqcapt19]

Are the control wires directly associated with the power wires in the conduit? If not you can't put them in the same raceway. See 725.48(B)(1) for Class 1 control circuits or 725.136(A) for Class 2 or 3 control circuits.

 

[electricus]

As a design issue, yes. It's much easier to troubleshoot problems if they are kept separate, even if interference may not be a problem itself.

If all you care about is Code minimum, that's a different story. I do a considerable amount of troubleshooting so I may have a different perspective than you have, if all you are concerned with is the initial installation.

Excellent point, I didn't consider it from a troubleshooting point.

don_resqcapt19

Are the control wires directly associated with the power wires in the conduit? If not you can't put them in the same raceway. See 725.48(B)(1) for Class 1 control circuits or 725.136(A) for Class 2 or 3 control circuits.​

This is also a good point.

For both of these points I'm now going to keep them separate.
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