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Old 11-03-2008, 11:43 AM   #1
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NM Wiring Located Near Heat Duct


I'm remodeling a bathroom and came across a slight predicament. When the house was built (mid 70's) the electrician had run a pretty decent amount of wires in the same "bay" as a heating duct (in a wall, not a cieling). When I ran wire for the new recessed lights, I followed suit. Now that I've had a few friends look over my handy work, I've gotten a comment that running my wiring in the same "bay" as the heating duct could violate code? Is this the case? I'm using NM wire and plastic boxes, if that makes a difference. I think his primary concern was with shorting (which shouldn't be a problem using all plastic) and also fear that the wire insulation could become dry and brittle. Any suggestions? Re-wiring really isn't an options. Would this violoate code? Thanks for your help!

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Old 11-03-2008, 12:11 PM   #2
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NM Wiring Located Near Heat Duct


Quote:
Originally Posted by Pineapple View Post
I'm remodeling a bathroom and came across a slight predicament. When the house was built (mid 70's) the electrician had run a pretty decent amount of wires in the same "bay" as a heating duct (in a wall, not a cieling). When I ran wire for the new recessed lights, I followed suit. Now that I've had a few friends look over my handy work, I've gotten a comment that running my wiring in the same "bay" as the heating duct could violate code? Is this the case? I'm using NM wire and plastic boxes, if that makes a difference. I think his primary concern was with shorting (which shouldn't be a problem using all plastic) and also fear that the wire insulation could become dry and brittle. Any suggestions? Re-wiring really isn't an options. Would this violoate code? Thanks for your help!
Is this a air return or an heating duct?

My undersanding is that the older NM had a lot more problems with becoming brittle than the newer pvc based stuff.

Jamie

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Old 11-03-2008, 12:16 PM   #3
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NM Wiring Located Near Heat Duct


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Is this a air return or an heating duct?
That's a really good question. I don't know how I'd tell just from looking at the duct? I don't really have a way of telling where it goes.
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Old 11-03-2008, 12:19 PM   #4
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NM Wiring Located Near Heat Duct


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That's a really good question. I don't know how I'd tell just from looking at the duct? I don't really have a way of telling where it goes.

Does hot air blow out of it or does it suck in air? Hold a sheet of paper up to it with the furnace on, a return will suck the paper in, a heat register should blow it just like a fan.

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Old 11-03-2008, 12:50 PM   #5
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NM Wiring Located Near Heat Duct


Therein lies the challenge. I only have access to the wall the duct resides in... so I'm not sure where it goes. If I had to guess though, I'd assume it's a heating duct. There is a second duct running up another wall in the room that I can see vents out into the hallway. That one is definitely an air return. So yeah, let's go with the assumption that this is a heating duct, not an air return.
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Old 11-03-2008, 01:08 PM   #6
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NM Wiring Located Near Heat Duct


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Originally Posted by Pineapple View Post
Therein lies the challenge. I only have access to the wall the duct resides in... so I'm not sure where it goes. If I had to guess though, I'd assume it's a heating duct. There is a second duct running up another wall in the room that I can see vents out into the hallway. That one is definitely an air return. So yeah, let's go with the assumption that this is a heating duct, not an air return.
I hope someone that can quote the NEC can jump in here. I thought I could find the section that talked about this, but I am not able to find it.

I found this page: http://advice.thisoldhouse.com/showthread.php?t=7972 It suggests that neither is really acceptable.

I thought I remembered someone on this site saying that you can use a return in some cases, but I can't find the post right now either, so don't take my word for that, I might be remembering that incorrectly.

Sorry I wasn't more help.

Jamie
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Old 11-03-2008, 02:01 PM   #7
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NM Wiring Located Near Heat Duct


Just to be clear here. I'm not going through the duct itself. Only the same wall as the duct. Basically, the wall is framed out to go around the heating duct and i've got some NM wire going through the wood studs that make up that frame.
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Old 11-03-2008, 02:33 PM   #8
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NM Wiring Located Near Heat Duct


There is no code violation to share the same bay with the NM cables. Return air or heated air. Just make sure the cables are not bundled together. They should be seperated and stapled if you have access to the cavity. The new NM is 90 degree "c" wire. There would not be enough heat generated to cause any issue.
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Old 11-03-2008, 02:47 PM   #9
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Beautiful! That's the answer I was looking for! Thank you!
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Old 11-03-2008, 08:42 PM   #10
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NM Wiring Located Near Heat Duct


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Originally Posted by J. V. View Post
There is no code violation to share the same bay with the NM cables. Return air or heated air. Just make sure the cables are not bundled together. They should be seperated and stapled if you have access to the cavity. The new NM is 90 degree "c" wire. There would not be enough heat generated to cause any issue.

If the entire joist space is used as air return, then you cannot run any wire through them parallel.
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Old 11-03-2008, 09:23 PM   #11
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NM Wiring Located Near Heat Duct


Well, not the entire space is taken up by the duct. Most wires are run through holes in the studs (perpendicular to the vent), though some are run along the stud (stapled to it, parallel to the duct). A picture could probably say 1000 words here, but we're talking about 1 foot of air space on either side of the duct!
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Old 11-03-2008, 10:02 PM   #12
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Well, not the entire space is taken up by the duct. Most wires are run through holes in the studs (perpendicular to the vent), though some are run along the stud (stapled to it, parallel to the duct). A picture could probably say 1000 words here, but we're talking about 1 foot of air space on either side of the duct!
Thats ok, there shouldn't be an insulation overheating problem, (even the old stuff should never get that hot). Seems good to me.
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Old 11-05-2008, 10:06 AM   #13
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NM Wiring Located Near Heat Duct


what is the closest nm can be to a heating duct?
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Old 11-05-2008, 12:02 PM   #14
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NM Wiring Located Near Heat Duct


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what is the closest nm can be to a heating duct?

It depends on the temperature of the heat in the duct, most ducts won't get that hot, it usually doesn't matter.
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Old 11-05-2008, 12:05 PM   #15
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what is the closest nm can be to a heating duct?
As close as you want it.

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