Running a wire through cold air return

[gygeneral]

I'm remodelling our upstairs washroom and wish to add electric in floor heating. I have two questions. First to you need a seperate circuit and second if yes then can I run the wire to the basement panel in the cold air returns?

The answer probably depends where I live, I live in Ontario Canada.

Any insight would be appreciated, thanks

 

[Justind97]

Yes it's legal. NO junction boxes in the ducts. Cold air return only.

Go to Home Depot and grab yourself the Ontario Electrical Code simplified. It's under $15.

 

[wyliesdiesels]

In the US you would need plenum rated wire.

 

[rlitman]

In the US you would need plenum rated wire.

Or sleeve it in EMT.

 

[Norcal]

Nor sure that any cables are allowed in air handling spaces, code is not handy ATM.

 

[sberry]

I am not sure about the code but have certainly seen it ran across thru it with cable. I don't recall seeing it on inspections, have seen it in 60-70 homes wired under masters.

 

[sberry]

As a guess since hi havnt opened the book for 15 years I got to say no to using an air duct as a raceway for wire. As I mention the only place I really have seen it is in basements where the joists were shafted in for returns and simply crossing them.

 

[wyliesdiesels]

Or sleeve it in EMT.

That doesnt make the wire less poisonus when it burns.

 

[The Cobbler]

In some of the housing projects I work in in Ontario, they ran BX thru the cold air ducts to upgrade to wired smoke detectors . just an FYI

 

[gygeneral]

Yes it's legal. NO junction boxes in the ducts. Cold air return only.

Go to Home Depot and grab yourself the Ontario Electrical Code simplified. It's under $15.

Good idea, it would be a nice resource to have. Thanks

 

[gygeneral]

So based on these answers the worst case I would need plenum rated wire to use the air return. No junction boxes which is not an issue. This is the easiest way to wire this without making holes in wall on the main floor. I'm going to pick up that book at HD and see if it says anyting. Thanks everyone

 

[rlitman]

That doesnt make the wire less poisonus when it burns.

That's immaterial, as any smoke from a burning wire wouldn't be in the plenum.

EMT is allowed to be run within plenums. There are no restrictions for what can be placed inside that EMT. THHN is NOT plenum rated, and yet it is fine, so long as it is inside the EMT. So is MC. NON-Metallic systems need to be plenum rated if used in a plenum. Metallic does not.
Refer to 300.22

I also know of no restrictions about junction boxes, though it seems like a bad idea.

 

[tyme2par4]

That doesnt make the wire less poisonus when it burns.

Plenum rating doesn't have anything to do with poisonous fumes. It's only smoke density.

 

[theoldwizard1]

In the US you would need plenum rated wire.

Or sleeve it in EMT.

SNORT ! Lots of Romex run through cold air returns in my 60+ year old house !

 

[johnnyradiant]

On one of my jobs I came across a house with wire running every which way in a return. The home owner or whoever he got to do the work abided by the no junction boxes part wholeheartedly. Just not the intent of that. When I got into it there was one wire nut just lying in the duct when I got to it. There was nothing protecting the lumex from being cut on the hacked holes either. Spent a few hours extra undoing that but the whole house should have been undone. Surprised it hasn't burnt down yet.

 

[LifeLongWNYer]

I would say that if you have a house fire, and it gets hot enough to burn the insulation of wire in a cold air return duct, and you haven't already left the premises, the smoke and gases from the other stuff burning will get you first.

There is a lot of plastic stuff to burn and give off bad gasses in your house, so that little bit of wire insulation isn't going to make things much worse.



.

 

[reader2580]

I had forced air heat added to a house 30 years after it was built. The ducts run through the basement and they just panned over joists for some of the cold air returns. There are wires running through some of the cold air returns and I was not going to reroute them.

Electrical inspector never said anything, but not sure he was in those areas of basement.

 

[gygeneral]

I bought the book Electrical Code Simplified at Home Depot today and here is what is says about this topic

 

[MrSurly]

THHN is NOT plenum rated, and yet it is fine, so long as it is inside the EMT. So is MC.
Refer to 300.22

I'm not the OP, not in Canada, but I have some confusion about 300.22(B). Maybe you guys can sort this out.

First, the way I read it is that wiring is only allowed through the duct IF it it for the express purpose of acting upon, controlling or sensing the air in the duct. So, for a damper, temp probe, t-stat, yes, but passing through wiring for other purposes (say, alarm wiring or room light) is prohibited.
<<300.22(B) shall be permitted within such ducts only if
necessary for the direct action upon, or sensing of, the
contained air.>>

And regular MC cable would be prohibited *unless* it was sealed; smoke tight/liquidtight
<<300.22(B)Type MC cable employing
a smooth or corrugated impervious metal sheath
without an overall nonmetallic covering,>>

Such as the FMT addressed in 360:
https://www.mikeholt.com/mojonewsar...lexible-Metal-Tubing-Article-360~20041108.php

I also know of no restrictions about junction boxes, though it seems like a bad idea.

It would seem that the language <<Only wiring methods consisting of> and a list of conduit types, but no boxes listed would prohibit boxes. The intent would seem to require *sealed* boxes, if any.
Also, EMT is OK, but nowhere are EMT *connectors* addressed.
It would seem to be the intent that EMT set screw couplings would fail the purpose and sealed (rain tight?) would be required.

 

[mrramsey]

The reason it is not allowed has less to do with smoke and more to do with fire. If the wire would short and spark ignition of a fire within the cold air return the return would act as a chimney and allow for the rapid spread of flames through the floor and or wall cavities.

 

[justsam]

Code legal or not,, this is one of the areas where I would just not do it, especially in the return. If there were to be toxic fumes, fire, etc. this would be a sure way to spread it thru out the building. Just a personal choice, I have no anecdotal stories to back it up.

 

[sberry]

In a house I don't pass wire thru a sheet metal duct, I will go around, remove, drill, do what I got to do to install a wire. I have seen a lot of it drilled thru wood floor joists where the bottom has been sheeted for return.
I would be really desperate and have absolutely no other choice beore it would occur to me to come up with something using the duct as a raceway. Doesn't mean I might not take advantage of something from joist to joist kind of deal.