Electrical Panels in Return Air

[lile001]

I've got a building where there is a mechanical space that is wide enough to walk in, and they have installed several electrical panelboards in the space. We are OK with working space rules, but the whole area is a return air plenum.

Now, as far as I knoow, EMT and wire is OK in an "other space for environmental air". But how about panelboards? Anyone have a clue?

 

[jeff43222]

I think the answer you seek is in 300.22(C)(2). Wiring methods are covered under 300.22(C)(1).

Although it sounds like it might be a bad idea, it seems to me that putting a panelboard in such a space would be code-compliant.

 

[ryan_618]

This is not a plenum, nor is it "other space used for environmental air". Take a look at the last sentace of 300.22(C), which will show that you are compliant.

 

[plate]

According to the NEC2005 Handbook Commentary (not code), "If the prime purpose of the room or space is air handling...then the restrictions in 300.22(C) apply...

In this case 300.22(C) (2) Equipment would apply.
Which in a nut shell says you can have a metal enclosure or non-metallic if it is listed for use.

 

[sandsnow]

I have walked in plenums. Some of old ones are gigantic. One huge return fan and corresponding supply fan. One wall is solid air filter, on the other side ducts take off to other parts of the building. If you turn the supply fan off, the positive pressure from the return fan blows the door out of your hand when you unlatch it. If you turn off return fan and leave supply fan on, you can't get the door open. These are not installed any longer. Too inefficient.

Now we have smaller air handlers, usually roof mounted. They are still big enough to walk in. The doors on the side will allow you access to either the supply fan, return fan or the air filters. Inside those doors is a plenum.

Anyway, I don't see enough info to judge this as a plenum or "other space."