Cold air return and electrical romex

The electrical wires pass thru the cold air return in a 1915 home.

How would you report this or is this acceptable. There is visible rust present from the detahed portion of the return.



See NEC Section 300.22©,
Exception: This section shall not apply to the joist or stud spaces of dwelling
units where the wiring passes through such spaces perpendicular to the long dimension of such spaces.

The exception to 300.22© permits cable to pass through joist or stud spaces of a dwelling unit. The joist space is covered with sheet metal and used as a cold-air return for a forced warm-air central heating system. Equipment such as junction boxes or device enclosures is not permitted in this location.

do they actually pass thru the return or is that the combustion relief duct?


It is a cold air return to an open basement.


OK…in addtional regards to this as joe has stated in 300.22 but another reason NM or non-metalic cables or raceways are not permitted in an environmental air space is because they give off toxic fumes when burned or super heated. However some thiungs like control and signal and communication wires are permitted if they ar plenum rated or installed in a raceway suitable for the space of application.

From what I see this is not something I would cover in art 300 © and I think (A) does not apply here…this is not the case of simply capping the bottom of the floor joists off to form a environmental air return…Sooo…

In my opinion not allowed in this nature…not to mention the point of entry into the duct itself is not sealed and so on. About all I can tell from this picture…

Yes…Yes…I am aware that romax can run through a fllor joist and the joists used as Environmental air return if run perpemdicular…BUT I do not see that as evidence here based on the way it is run from the obervation…also in 300.22© Exp. is where you are going to see that above allowance…

However this is for cold air returns for a forced warm air central heating system…sheetmetal along the bottom of the joists and studs type of application to meet this exception.

Other than that…being brief…See Art 300.22(B) for wiring methods allowed…Type MI, Type MC with smooth or corrugated impervious metal sheath without an overall non metallic covering…and it goes on more which really is beyond the scope of a HI ELE inspection.

This is a mechanical, not an electrical issue.

NO utility can run through an HVAC duct.

HVAC has priority over ALL trades in referance to location. No hits are allowed with any HVAC device.

Just for my own curiosity. How would you correct the issue in the photo.

Would you relocate the cold air return. There where about 3 or 4 others located in the basement. Or would you move the wiring. This seemed to be the more difficult of the two.

Thank you for all your responses. And I appreciate your knowledge to help me become a better inspector.


Ahh…now we are getting into what would a ELE contractor do…different than just spitting out code and violations…

As a ELE I would probably suggest placing the wires in a proper aux. junction before they enter into the duct itself…and then re-route the wires under it to another junction location.

Their are a few other ways to do this as well…on a side note most HI’s when they see something like this should steer way from telling them how to change it becuase chances are happy homeowner will try it themselves so always refer to a EC to give them suggestions on how to fix.

I guess alot also has to do with if that duct is turning down and the wires are not actually going through a duct but running along the end of it…would be easy to view from that gapping gap in the front of the duct return.

What you will get from a realtor is…it has been their fine for years and as harmed no one yet…where have we heard that before but at the end of the day chances are they wont touch it even if you do make the recommendations.

Again if it were me…I would simply place probably a 4 x 8 box…going from memory here as I would have to count out that wire balance and let it size the junction needed but it is the cheapest solution as opposed to buying pipe and trying to cut and sleeve and swear it is for protection only and so on…and so on…as a ELE we would just get it done and the junction would be my call…since it is clear it would be access worthy and once the wires are freed up…the box would sit nice ont he beam…and of if you need more space…throw on an extention to increase the need.

Thats the easy way…versus just leaving it and praying it never is an issue as I would be more concerned with the metal rubbing the jackets as the duct rattles and so on from the air movement.

Would you like some additional methods to get around this?

Unless your area works under a strange mechanical code that is simply not true.

Many times I install wiring in and on ducts that has to be there, motirized dampers, duct smoke detectors, booster fans, exhaust fans etc.

It is a common pratice for NM to be run across a duct imade of a stud cavity in a dwelling unit.


Yep the NM in a stud cavity is within the exception and allowed . In general terms the design of that cavity has to be specific in terms of sheet metal along the bottom to form an environmental air return.

 In the case of the picture I dont see this happening ( would you agree as my eyes sometimes are not good with small

 To David....spoken like a true HVAC man...thehehe....I say the same thing to the HVAC man all the time..HEY stuff will KILL ya...don't run any HVAC around my wire...thehehe

In residential wiring their is not written rule to WHO gets in their first...however I like to get in after both the plumber and HVAC guys are gone for many reasons...

1.) I just may be able to use any chase they make for their duct work so I dont have to drill as many holes…lol
2.) The wont try to attach anything to my wires…
3.) I dont have to worry about them cutting something out of the way and not telling me…(boy bob or joe…has that ever happened to you guys…:()

But as for them having FIRST dibs a nice virgin stud wall…they better get out of my way…I got the right angle drill with 4’ extention from milwaukee way ahead of um.

Here’s what the exception to © permits:

lol…pictures are worth a thousand words…thanks JOE…

You know their are many AHJ’s that do not even allow this any longer even if the NEC supports it. They use their basis on the fact that NM when burned or super heated gives off toxic fumes and thus refuse to allow it and in most cases insist the HVAC contractor run actual duct lines instead and allow the electrical contractor to keep on what they are doing…

In our area for example…they will not allow the use of the cavity as a return any longer but it is currently being reviewed because some high ranking members of the HVAC contractors board around here are fighting it.

Personally…I dont see a problem with it as what are the chances of heating that NM on a cold air return unless the house is burning down…which means you have other things to worry about…lol

I agree:cool:

My post was really aimed at the HVAC man making a general statement that it is never allowed.

I think if the duct guys want privacy they need to run a complete duct not just box in a stud cavity and claim they own 100% of that space.:stuck_out_tongue: