24v dc

[factoryrat]

I have a 24 volt dc, 2.5 amp, power supply. Does the NEC allow me to run these 24v dc wires in the same conduit with #12 AWG, 120v ac, conductors? Or must they be in separate conduits?

Code references would be appreciated. Thanks.

 

[petersonra]

Re: 24v dc

I have a 24 volt dc, 2.5 amp, power supply. Does the NEC allow me to run these 24v dc wires in the same conduit with #12 AWG, 120v ac, conductors? Or must they be in separate conduits?

Code references would be appreciated. Thanks.

In general the answer is they can occupy the same raceway.

The size of the AC wires is not an issue.

300.2 (C) Conductors of Different Systems.
(1) 600 Volts, Nominal, or Less.
Conductors of circuits rated 600 volts, nominal, or less, ac circuits, and dc circuits shall be permitted to occupy the same equipment wiring enclosure, cable, or raceway. All conductors shall have an insulation rating equal to at least the maximum circuit voltage applied to any conductor within the enclosure, cable, or raceway.

However, it is possible the 24V wires (or even the 120V wires) are part of a limited energy circuit. You are not usually allowed to run limited energy circuits in the same conduit as non-limited energy circuits. Article 725 covers limited energy circuits, but it is written so poorly that it is not readily understandable.

If this is part of an industrial machine, NFPA79 rules would apply, which tend to be less restrictive than NEC rules.

 

[dlhoule]

Bob is correct.

300.2 (C) Conductors of Different Systems.
(1) 600 Volts, Nominal, or Less.
Conductors of circuits rated 600 volts, nominal, or less, ac circuits, and dc circuits shall be permitted to occupy the same equipment wiring enclosure, cable, or raceway. All conductors shall have an insulation rating equal to at least the maximum circuit voltage applied to any conductor within the enclosure, cable, or raceway.

Congrats on your 1st post.

If you are in a factory, I would just like to point out that it is not always a good idea to run the low voltage in the same conduit, especially when it is higher (440 volts. ) In cases where motors or other equipment is being turned on and off it can wreak havoc on low voltage controls when in the same conduit.

 

[infinity]

The issue here is the classification of the power supply. If classified as Class 2 or 3 than the wiring can not be in the same raceway as power conductors regardless of the insulation type or voltage.

In cases where motors or other equipment is being turned on and off it can wreak havoc on low voltage controls when in the same conduit.

Can you elaborate on how the control wiring will be affected if in the same conduit as the power wiring?

 

[dlhoule]

Can you elaborate on how the control wiring will be affected if in the same conduit as the power wiring?
_________________
Trevor

How come nobody asks me easy questions?

A lot of the PLC's have modules that have fairly low trigger points and will have an input turned on by an induced voltage in the dc wiring.

That's my understanding of it. I do know that when you trouble shoot something for more than a day or two and just happen to notice the only time you get this unwanted input is when there is a change in what is happening in AC wiring and you separate the low voltage control from the higher voltages with a separate conduit. No more problems.

 

[hockeyoligist2]

Can you elaborate on how the control wiring will be affected if in the same conduit as the power wiring?
_________________
Trevor

How come nobody asks me easy questions?

A lot of the PLC's have modules that have fairly low trigger points and will have an input turned on by an induced voltage in the dc wiring.

That's my understanding of it. I do know that when you trouble shoot something for more than a day or two and just happen to notice the only time you get this unwanted input is when there is a change in what is happening in AC wiring and you separate the low voltage control from the higher voltages with a separate conduit. No more problems.

I agree with larry i've ran in to this many times myself, and it is hard to troubleshoot if you don't know they are there.

 

[factoryrat]

This is just a dc power supply (24v dc ? 2.4 amp capacity). I have to power up a Bar-Code reader. It will read a bar code that is attached on the body of the car. It carries information to make sure the car gets painted the correct color and maybe some other information I am unaware of. If I run it in the conduit with the 120v ac I do not see any problems with induced voltages or noise. The ac circuit wire draws a couple of amps, maximum. I just wanted to be sure I was not doing something in violation of the NEC. And with all of your great answers I feel confident I will be code compliant. Also if I am questioned on how I install this I have a code reference I can quote. Thanks to all of you!