Can panelboards be installed in a return air plenum? I have a situation where there is an entire room under negative pressure (a true return air plenum) not just the space above a suspended cieling. There is an existing panelboard in the room and I'd like to install another one. Can anyone think of anything that would prevent this?
Panelboards in a plenum
- Thread starter lile001
- Start date
- Status
- Location
- Windsor, CO NEC: 2023
- Occupation
- Hospital Master Electrician
This is an interesting idea. Steve, I've been looking at your reference, and the wording of the section kinda stinks. I'm having trouble with the last sentence.
"I've gone cross-eyed." - Austin Powers
If the prime reason this room exists is not for air handling, then this section cannot be used, can it? Or can it?
"I've gone cross-eyed." - Austin Powers
websparky
Senior Member
- Location
- Cleveland, Ohio
Does the panel meet this requirement?
- Location
- Illinois
- Occupation
- retired electrician
George,
If the primary purpose of the room is not air handling, then you don't have to apply the rules in 300.22. Standard wiring methods would be permitted.
Don
If the primary purpose of the room is not air handling, then you don't have to apply the rules in 300.22. Standard wiring methods would be permitted.
Don
- Location
- Windsor, CO NEC: 2023
- Occupation
- Hospital Master Electrician
Don, what if #2 in the room's purpose is as a cold air return?
I'm not understanding this.
I'm not understanding this.
Websparky:
The NEC doesn't consider this a "duct" or a "plenum". It is a "other space used for enviromental air". Read on to 300.22(C).
BTW: lile001 called this space a plenum, but if it is a "room", then it is not the NEC definition of a plenum.
George:
It it's #2 purpose is cold air return, then like Don said - standard wiring methods apply. It's just like the office I am sitting in now. The HVAC air passes through this room, but thats not why they put this room in.
If they had specifically put this room in in order to channel air through it, then 300.22(C) applies.
In either case, a there is nothing prohibiting a panelboard.
The NEC doesn't consider this a "duct" or a "plenum". It is a "other space used for enviromental air". Read on to 300.22(C).
BTW: lile001 called this space a plenum, but if it is a "room", then it is not the NEC definition of a plenum.
George:
It it's #2 purpose is cold air return, then like Don said - standard wiring methods apply. It's just like the office I am sitting in now. The HVAC air passes through this room, but thats not why they put this room in.
If they had specifically put this room in in order to channel air through it, then 300.22(C) applies.
In either case, a there is nothing prohibiting a panelboard.
300.22 Wiring in Ducts, Plenums, and Other Air-Handling Spaces.
The provisions of this section apply to the installation and uses of electric wiring and equipment in ducts, plenums, and other air-handling spaces.
(C) Other Space Used for Environmental Air. This section applies to space used for environmental air-handling purposes other than ducts and plenums as specified in 300.22(A) and (B). It does not include habitable rooms or areas of buildings, the prime purpose of which is not air handling.
FPN: The space over a hung ceiling used for environmental air-handling purposes is an example of the type of other space to which this section applies.
I agree with George. It is poorly written. If article 300.22 covers wiring in air handling spaces, the wiring in these spaces should be covered by either (A) (B) or (C). C. states: It does not include habitable rooms or areas of buildings, the prime purpose of which is not air handling.
I guess after beating my head against the wall for a while. It means that an area that has as its primary purpose something other than air handling falls outside of 300.22.
The provisions of this section apply to the installation and uses of electric wiring and equipment in ducts, plenums, and other air-handling spaces.
(C) Other Space Used for Environmental Air. This section applies to space used for environmental air-handling purposes other than ducts and plenums as specified in 300.22(A) and (B). It does not include habitable rooms or areas of buildings, the prime purpose of which is not air handling.
FPN: The space over a hung ceiling used for environmental air-handling purposes is an example of the type of other space to which this section applies.
I agree with George. It is poorly written. If article 300.22 covers wiring in air handling spaces, the wiring in these spaces should be covered by either (A) (B) or (C). C. states: It does not include habitable rooms or areas of buildings, the prime purpose of which is not air handling.
I guess after beating my head against the wall for a while. It means that an area that has as its primary purpose something other than air handling falls outside of 300.22.
- Location
- Windsor, CO NEC: 2023
- Occupation
- Hospital Master Electrician
Well, at least I don't feel like a total putz then.dlhoule said:
websparky
Senior Member
- Location
- Cleveland, Ohio
Steve,
The OP said it IS a plenum. YOU are assuming it is not. There are "rooms" in large facilities that are in fact "plenums". If this is the case as the OP said, then your reference is incorrect. When the OP ever comes back to fill us in, then we will both know the real answer!
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