Switch in Cold Air Return

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Old 01-12-08, 12:43 PM
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Switch in Cold Air Return

The space between 2 studs in a bedroom wall is being used as a cold air return for the heating system. Can I put a switch for a light in this cold air return?
 
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Old 01-12-08, 12:49 PM
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No.



Fifteen characters.
 
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Old 01-14-08, 08:24 AM
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You may install wiring in a cold-air return, but you cannot use PVC cable (romex) or PVC boxes. You need to use a steel box and type MC (metal-clad) cable or EMT conduit. Note that either the MC cable or EMT conduit needs to terminate at a metal box on both ends, so you'll have to plan the rest of the project accordingly. Also the penetrations into the air-handling space where the cables or conduits enter need to be sealed with a fire-rated caulk.
 
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Old 01-22-08, 05:17 PM
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Is this for fire safety reasons? Code? I ask because my house (built '05 - Alberta, Canada) has romex passing through the cold air return, as well as a central vac tube. This is both in the basement ceiling and main floor ceiling. None are sealed. with any kind of caulk/foam. Is this something I should address before drywalling/closing up the basement ceiling?
 
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Old 01-22-08, 05:59 PM
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flaming PVC

liberates poison fumes. Smoke inhalation is the major cause of death in struture fires, ergo. keep PVC out of moving air cavities (plenum).
 
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Old 01-23-08, 06:27 AM
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What is it with Canadian contractors?

has romex passing through the cold air return, as well as a central vac tube.
I'd swear I just saw that on Mike Holmes two days ago!

Tom
 
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Old 01-23-08, 08:43 AM
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What did Holmes say about it?

I figured I'd illustrate the situation. This was taken by placing my camera inside the cold air return joist bay, in the floor of the second story of my house. The pvc central vac pipe and all those wires continue on downwards in this return air cavity, which leads straight down into the basement (you can see the edge of the cavity in the middle of the picture -- the end of this return bay is not blocked off...). This is the only return for the second floor.





I think Romex in cold air ducts allowable by code here in Alberta, but I'm not 100% sure. Definitely against code in hot air supply ducts. I'll check tonight. Is this in the electrical code down there?

As an aside (probably more suitable for HVAC forum), this return has a 14x6 opening in the wall, but is connected to that cavity/'duct' via a 6" hole in the joist separating the two. Not sure if this is an issue or not (since effectively the return hole "area" is now limited to pi*3*3 < 14*6, which is supposed to service the entire upstairs).
 
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Old 01-23-08, 08:48 AM
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Wink

Like you said go ask code where you are. I know here it is ok. You just cant run a gas line in the cold air return .
 
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Old 01-23-08, 09:20 AM
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In dwellings, NEC allows romex to pass through air handling spaces perpendicularly (across the short dimension) provided that the penetrations are sealed. It does not allow romex lengthwise in an air return, nor does it allow plastic boxes in air returns. Your picture pretty much follows these rules: metal box, shortest crossing, foam sealant, that one piece is a little longer than it probably should be but there may have been no other practical way to install it.

In buildings other than single family homes, no romex is allowed in air handling spaces which includes the space above a suspended ceiling.

I don't know about the PVC vac tube. It seems like a bad place for it to be, but I don't know what code(s) regulate installation of a central vac. It's possible it was installed after the mechanical inspection.
 
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Old 01-24-08, 07:37 AM
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If I recall on the Mike Holmes show, there was an actual metal duct that was used. Big NO NO. I can see now from the picture that this is the empty space in the wall. There are codes that allow this kind of thing to be done properly, as other have said. It just seems to me that you have to be really careful around there so you don't hang a picture or something on the other side and leave a nice hole in your "duct".

Good luck!
 
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