Old Plenum as a wire chase

[Ellement]

Hi, I know you can't run wiring through air plenums but in this case I was wondering if there were an exception.

An older home with a forced air oil furnace is to be removed and new ecotherm electric wall mount heaters are to be installed, we were wondering if using the old unused plenums (6?air returns) to chase the wires up to the 2nd floor to feed the new heaters would be OK?

I?m thinking that if we seal off the basement ceiling passage to the ducts leading to the upper floors with plywood and drilling holes to pass the wiring, so that the old ducts now do not pass air but act as a tin lined wall cavity?. Please let me know your thoughts on this.

The home is 70 years old and to pass wires to each individual heater could only be done externally otherwise.


Thanks in advance.

[electric-ed]

I don't see any rule prohibiting what you are proposing.

Although there is no requirement for it, some inspectors might want the metal duct bonded to ground.

Ed

[CRM]

I agree with Ed, if I was doing it, I would use bx cable rather than loomex, I feel it would be safer when pulling the cable through the tin duct.

[bigrockk]

Good idea CRM, using Bx in the duct makes sense.
It would most likely be quite easy to "snag" the loomex on a sheet metal screw in the duct and do some damage. Using Bx might save a guy some rework later.