ID of Grounded Circuit Conductors...

[douglasgr]

Hey all,

I'm having a debate with a co-worker over NFPA 79 14.2.3.2. My question is this, when grounding the common side of a dc power supply (24vdc), which conductor is the WHITE w/ BLUE stripe? I say it's the dc common that runs through-out the 24vdc circuit. For example, if I had a 24vdc light on a control panel, the (+) side would have a blue conductor and the (-) side would have the white w/ blue striped conductor. He says that both would be blue, and only the conductor running from the dc power supply to ground would be the white with blue striped conductor. Who's right and is there somewhere I can find an example of this?

Thanks,
-Doug Greig

 

[Smart $]

Don't know word one of NFPA 79. I've worked in and on many industrial control panels and have never seen a white w/blue tracer used for internal wiring. The only place I've run across any is as one conductor of twisted-pair communications cables. All 24vdc wiring has been blue, no trace.

Sounds to me like an attempt to implement a new standard, one I have yet to see in practice.

 

[jim dungar]

UL508A and NFPA79 both encourage, but do not require, white w/blue tracer for the identification of grounded (CURRENT CARRYING ) DC circuit conductors. This means all of the conductors not just the bonding connection.

 

[todd99]

Look at it this way, what color scheme do you use for your 120VAC circuits? Red for un-grounded conductor and white for the grounded conductor right?

If you had a 120VAC light, you would have a red wire to on side of the coil and white to the other side. By using your friends logic they would both be red, and the only place you would have white would be from secondary of the control x-former to the equipment ground. I don't think anyone would agree that is appropriate, regardless of how familiar you are with NFPA79 or any other machinery standards.

Todd