Ductwork and MC

F

Fordean

Senior Member
Location
New Jersey
Occupation
Electrical Contractor
Trying to figure a route 2 floors up
I read you can run mc cable in the ductwork on the exhuast side True or false?
 
augie47 said:
No, 300.22
Click to expand...
Retired and just wondering if you can install a 3 to 4' piece of greenfield thru a roof top return duct to feed rooftop HVAC unit safety switches. Did that years ago on 20 to 50 ton units to avoid drilling a hole thru flat roofs that even with a 6" high metal box filled with quality roof tar would some times leak. Had one of these leak where water entered thru the top of a1" EMT set screw coupling a few feet below roof and into a size two 480 starter blowing it up. We would run the greenfield thru a chase nipple secured to duct work then seal it up with fire stop chalk. Used a 90 degree greenfield to feed into back of the safety switch and fire stoped that also.
 
What type of floors are we talking about?
Do you have fire stopped flashing where duct passes through floors or
just band flashing holding the Duct for movement?

I would run the circuit right with the Duct run. Noting the framing spacing I'd look at the corner of the run and consider lifting the flashing to see if there is a drill space or enlarged opening you can use. Remember to note cross brace framing.

You can also install like framing to use as a securing method in vertical.
 
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