Romex running through plenum spaces

Status
Not open for further replies.
J

jeff48356

Senior Member
Location
Livonia, Michigan
What are the codes in Michigan regarding Romex within cold-air cavities (plenums)? I know that the holes in framing members need to be fire-caulked. But can wires be run along studs as shown in the picture?
 

Attachments

  • IMAG0339.jpg
    IMAG0339.jpg
    82 KB · Views: 22
According to the NEC the horizontal cable at the bottom is permitted the vertical cables are not. {300.22(C)Ex.}
 
I agree with infinity. You can traverse the plenum but you cannot run parallel with it. If they don't need the entire space then just put a 2x4 on each side to box the wire.
 
There appears to be ductwork to the left of the Romex.. normally the joist space is a dead air space and not used for air handling.
Eta: I missed what I assume are ductwork brackets on the stud faces. Still, there's no way to know for sure at this point if those cavities are being used for environmental air, or a duct work will eventually be put in.
 
IMO, these are just transfer grills. A hole in the wall. Not directly connected to the return air system.
The actual return air duct is somewhere else in the dwelling, which is, most likely, directly connected to the furnace.
I approve this installation. :)
 
rcarroll said:
IMO, these are just transfer grills. A hole in the wall. Not directly connected to the return air system.
The actual return air duct is somewhere else in the dwelling, which is, most likely, directly connected to the furnace.
I approve this installation. :)
Click to expand...

If they were wouldn't there be one on each side of the wall?
 
rcarroll said:
IMO, these are just transfer grills. A hole in the wall. Not directly connected to the return air system.
The actual return air duct is somewhere else in the dwelling, which is, most likely, directly connected to the furnace.
I approve this installation. :)
Click to expand...


Ron a transfer grill would need a grill on both sides. It is not set up that way at all. Looks like the stud space is the plenum which is connected to duct in the basement or crawl.

I just can't see it as a transfer grill.
 
Dennis Alwon said:
Ron a transfer grill would need a grill on both sides. It is not set up that way at all. Looks like the stud space is the plenum which is connected to duct in the basement or crawl.

I just can't see it as a transfer grill.
Click to expand...

That's the way I see it too based on the description in the OP. Too bad the photo is cut off on the bottom that might provide some further details.
 
infinity said:
That's the way I see it too based on the description in the OP. Too bad the photo is cut off on the bottom that might provide some further details.
Click to expand...
I have to believe there is a grill on the bottom of the wall. There is no where else for the air to go. The top plate is not cut out.
BTW, thanks for not beating me up on my post! :p
 
Follow up: I had the rough inspection yesterday, and the inspector said that the vertical runs, as well as those that terminate with a box within the air space, need to be put into a sleeve of flexible metal conduit that goes to an area outside of the cold air space. I forgot to ask.. do I need to place anything onto the FMC in that area, such as a red bushing? I realize, of course, I need a proper flex fitting at the box where it attaches to it.
 
While MC cable does not require bushings, AC and FMC into which you install conductors do, so, yes.
 
rcarroll said:
I have to believe there is a grill on the bottom of the wall. There is no where else for the air to go. The top plate is not cut out.
BTW, thanks for not beating me up on my post! :p
Click to expand...
Some HVAC guys prefer to put return air inlets high on the wall, it is a design issue for them, and makes some sense for cooling purposes - warm air will be drawn from near the ceiling and run through the system to cool it. If you draw return from the floor - you never really exchange any the air near the ceiling without additional circulation methods.

Those stud bays likely are open or at least partly open on the bottom plate to allow air to flow into floor joist space and eventually into main return air duct.
 
jeff48356 said:
Follow up: I had the rough inspection yesterday, and the inspector said that the vertical runs, as well as those that terminate with a box within the air space, need to be put into a sleeve of flexible metal conduit that goes to an area outside of the cold air space. I forgot to ask.. do I need to place anything onto the FMC in that area, such as a red bushing? I realize, of course, I need a proper flex fitting at the box where it attaches to it.
Click to expand...
Kind of a dumb requirement if you think about it. First no wiring methods are permitted in a plenum unless it supplies something acting upon the environmental air or is specifically permitted otherwise. Putting the cable in FMC doesn't change anything here, especially when one considers typical FMC isn't very isolating air flow wise. Putting in a solid walled tube of some sort to create a "non plenum space" makes more sense.
 
Status
Not open for further replies.
Top