AC/DC SEPARATION IN PANELS

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plcman777

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I've been told by our inspector that I must separate the AC and DC in all my Electrical Control Panels. I've been doing this for twenty years and have never seen a panel in such a way.

I seem to remember that there was an exception for factory assembled control and/or UL Listed control panels that allowed AC and DC in the same panduit as long as the voltage rating on the insulation was equal or greater than that of the highest voltage in the panduit.

Our panels will all be UL Listed.

I built panels for a panel shop in the past and they used an exception, but I can't recall which.

Any help would be greatly appreciated.

Thanks
 
Re: AC/DC SEPARATION IN PANELS

We always did this in MCCs. Common AC control wiring was simply identified with red MTW wire, AC separate control with yellow, and DC with blue.
We always assured that there be a warning sticker of the outside door/cover that advised if the electrical interlock did not disconnect power within the emclosure, i.e. separate control which derives its power from ourside the enclosure and was not disconnected before the enclosure door was opened.
This may be foreign to your inspector.
Should the enclosed control that you are referring to be UL listed then it's not his call.
 
Re: AC/DC SEPARATION IN PANELS

Yes, I agree, this is what I'm talking about.

What I need is the NEC exception that I can show my inspector.

Keep the input coming.
 
Re: AC/DC SEPARATION IN PANELS

This is not an NEC issue. This is an NRTL listing issue. The NEC does not apply to "factory built" panels/equipment.

The NEC does not differentiate between AC and DC, all it wants is insulation for the highest voltage. Of course the NEC does address segregation if you are using 725 Class 1, 2, or 3 low voltage circuits.
 
Re: AC/DC SEPARATION IN PANELS

generally speaking there is no requirement to seperate ac and dc voltages. while a common practice (and usually a good one) there is no requirement to do so, and these days with panels being made as small as possible, its difficult to always arrange to do this.


Most of the confusion over this issue comes not from dc circuits but running analog circuits with 480V lines. This is a bad idea because most of the time shield cable insulation is only rated for 300V (or sometimes less). This obviously is not allowed. Its also a bad idea because you can get induced noise from the higher voltage wires onto the signal cables.

I'm not sure what inspector you are refering to but factory assembled panels are not covered under NEC rules. In many areas of the country localities now require UL listed control panels, but the local AHJ generally has no authority to inspect the factory assembled panel OTHER than to insure the installation requirements have been met.
 
Re: AC/DC SEPARATION IN PANELS

OK, here is my dilema. I have a large number of new factory built panels that the local electrical inspector wants to red tag for nonseparation. Also, I am building a large number of panels myself with the factories supervision and plans. These also will be red tagged for nonseparation. I can't find the exception that allows us to do this. All these panels will have a UL listing when complete.

Thanks for all the help.

[ November 02, 2004, 02:25 PM: Message edited by: plcman777 ]
 
Re: AC/DC SEPARATION IN PANELS

Jim Dungar cited the appropriate Article (725) if any of the circuits involved are Class 1, 2 or 3.(See the Article for the definitions) Otherwise, Section 300.3(C)(1) applies:
( 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.
Click to expand...
 
Re: AC/DC SEPARATION IN PANELS

I'm curious how you plan to get a UL listing for a control panel you plan to build yourself. Are you a UL listed panel builder?

You can have UL come in and inspect it after the fact but this is very pricey.
 
Re: AC/DC SEPARATION IN PANELS

Thanks for the code info. In reply to Petersonra; you are correct, we are having UL out to List our panels and yes it is exspensive.
Ouch.
 
Re: AC/DC SEPARATION IN PANELS

Originally posted by plcman777:
Thanks for the code info. In reply to Petersonra; you are correct, we are having UL out to List our panels and yes it is exspensive.
Ouch.
Click to expand...
why not just have a UL panel builder make them for you? in many cases due to volume discounts panel builders get from manufactruers, you can get the whole thing built to your prints for not much more than the parts would cost you. In some cases it costs you less to have it built (labor and all) than what you pay for the parts alone and you don't have to mess with having UL come out and inspect them at $1000 or more each.
 
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