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wiring in return air

Posted By: lite bulb

wiring in return air - 02/16/10 03:27 PM

I am remodeling my kitchen and came across this problem. The wall studding and wall board is used as a chase for a return duct and I would like to put a receptacle in that chase, if I use m/c cable and a metal box can I put this recept. in this chase.
Posted By: electure

Re: wiring in return air - 02/16/10 04:05 PM

If I understand you correctly, it's a ducted return running through the chase, and not an actual chase for the handling of environmental air.

Is the receptacle going to be accessible after you're finished?
Will the cord have to run through a hole in the drywall?


.

Posted By: gfretwell

Re: wiring in return air - 02/16/10 06:35 PM

If this stud bay is the duct I think that you will be sucking dust into the receptacle, eventually packing the enclosure you added.
Think about the case of your PC where the air comes in.
Posted By: resqcapt19

Re: wiring in return air - 02/17/10 02:43 AM

This would be a 300.22(C) installation. It looks like 300.22(C)(2) would permit this.
Posted By: Rewire

Re: wiring in return air - 02/17/10 03:31 AM

Originally Posted by resqcapt19
This would be a 300.22(C) installation. It looks like 300.22(C)(2) would permit this.
This is correct we have had to do this where return air space and receptacles were in the same spot
Posted By: lite bulb

Re: wiring in return air - 02/17/10 04:14 AM

What I'M saying is in the basement they panned off two bays for the return then over the panning there is a partion wall that is just studded out and drywall with a register grill, the bottom plate is cut out for the return air to flow down to the panned area I would like to put a recept in the wall chase that is really a return duct. The wiring will be running thru the partion wall and stopping in the wall chase return with a recept using m/c cable and a metal box cancealed in the wall.
Posted By: Rewire

Re: wiring in return air - 02/17/10 04:36 AM

you are good to go.The method is approved see 300.22(C)(2)
Posted By: Alan Nadon

Re: wiring in return air - 02/17/10 06:28 PM

Wiring can pass through (across) the stud space used as a return air (duct). A box and receptacle in that space would be a violation.
If the receptacle will be mounted above the register grill, a piece of wood across the space would effectively seperate the return air (duct) part of the stud space from the part with the receptacle.
Posted By: Rewire

Re: wiring in return air - 02/18/10 01:17 AM

Originally Posted by Alan Nadon
Wiring can pass through (across) the stud space used as a return air (duct). A box and receptacle in that space would be a violation.
If the receptacle will be mounted above the register grill, a piece of wood across the space would effectively seperate the return air (duct) part of the stud space from the part with the receptacle.
Whats your code reference
Posted By: lite bulb

Re: wiring in return air - 02/18/10 02:37 AM

Thanks for everyones reply.
Posted By: George Little

Re: wiring in return air - 02/18/10 02:56 AM

Alan, when you read 300.22(C)(2) Exception it tells us that "This section (meaning Section 300.22(C)) does not apply to the stud spaces of dwelling units.
I've had this discussion with Jeff Sargent from NFPA and that's his understanding also. Job is approvable.

For the sake of the disbelievers, I've seen contractors take a piece of metal panning material 3 by 24" and nail it on above the box and band it around the box and nail it below the box. Now you've divorced the wiring from the air flow.
Posted By: leland

Re: wiring in return air - 02/18/10 04:56 AM

Very interesting. I'm going back to 'most' of my jobs and do it the easy way!!!

Learned something new today. Tanx!
Posted By: Rewire

Re: wiring in return air - 02/18/10 03:09 PM

The exception is for wires passing perpendicular you are still allowed to run horizontal.
Posted By: Alan Nadon

Re: wiring in return air - 02/18/10 06:31 PM

Rewire. I was looking at the same place you were, but I think we have different images of what the metal box is that was going to be used. You are thinking, solid box suitable for a dust enviroment I pictured a standard metal device box with screw holes, etc. Could be we are both right or both wrong.
I would have to see it to judge it. Guess that is why inspectors still make house calls.
Posted By: Rewire

Re: wiring in return air - 02/19/10 03:07 PM

I used a 1900 box with a 4x4 block of wood covering the back ran emt horizontaly from the adjoing stud void this was the fix I cleared prior with the local AHJ.

Posted By: electure

Re: wiring in return air - 02/19/10 03:53 PM

I see what you're trying to do now... smile

The last time I did this, I used a putty pad to wrap the box.
Posted By: gfretwell

Re: wiring in return air - 02/19/10 07:06 PM

Caution, I have my HVAC hat on.
As a design issue I would want the box sealed to the plenum air, just so it does not become part of the return venting system and pack with dirt. George's idea of the metal deflector would work but you are also compromising the effectiveness of that plenum for returning air. If the HVAC guy computed that he needed a 14.5 x 3.5 duct, you have just choked that down to 11 or 12 inches and if it is not a smooth transition the turbulence effect makes it worse than that.
I doubt they really slice things that finely in residential systems but I also think they are likely to err on the small side most of the time and make ducts smaller than they should be. This will only make that worse.
I agree the electrical code may be somewhat ambiguous on this but you could have an HVAC issue.
Posted By: HotLine1

Re: wiring in return air - 02/19/10 09:07 PM

This sounds like a really good idea....

From the words of Rewire...

"this was the fix I cleared prior with the local AHJ."

Posted By: harold endean

Re: wiring in return air - 02/20/10 05:58 PM

You might also want to check with any fire marshal. Where I am from, the fire sub code people do not want any wire in any duct work.
Posted By: Tesla

Re: wiring in return air - 02/20/10 06:29 PM

I like the fire putty pad solution a lot.

You've stopped dust intrusion and addressed fire transmission at one stroke.

Sweet.
Posted By: SteveFehr

Re: wiring in return air - 03/02/10 07:01 PM

Originally Posted by resqcapt19
This would be a 300.22(C) installation. It looks like 300.22(C)(2) would permit this.
300.22(C) doesn't apply here, 320.22(B) does. As soon as you tack that pan up, the joist space becomes a duct. The ONLY boxes allowed in ducts are those required by function to be there- smoke sensors, dust sensors, etc. Only cables connecting to these boxes are permitted by 320.22(B).
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