# Drop ceiling? wiring



## RePhase277 (Feb 5, 2008)

Romex isn't a plenum-rated cable, if that's what you're using. You could use MC or conduit and it would probably be OK.


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## frenchelectrican (Mar 15, 2007)

dinlugoj said:


> The hallway will be finished as a regular ceiling. with a return air in there.
> Then he wants to build an arched decorative ceiling below the regular ceiling and leave a gap all around the walls so the air will return to the return duct.
> The inspector dont allow two drops for the ceiling for two high hats.( romex)
> What do you think?


If you plan to use the supended ceiling as return air plenum area. the romex is not allowed. It do cover both resdential and commercals locations. 



RePhase277 said:


> Romex isn't a plenum-rated cable, if that's what you're using. You could use MC or conduit and it would probably be OK.


Unforetally RePhase277 is correct on this and this rule been in enforeced for very long time. 

I will just used MC or EMT conduit and be done with it.


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## splatz (May 23, 2015)

If I am reading this right, there's a drop ceiling and a decorative drywall ceiling below it. The return air duct is in the drop ceiling. There is a gap around the edge of the decorative ceiling for return air to get to the duct. 

You want to run romex to cans that are between the drop ceiling and the decorative ceiling. The question is, is the space between the drop ceiling and decorative ceiling now a plenum space used for return air? I'd certainly say it is, and romex is out. 

In a situation where it there are two ways to look at it, you'll want to err towards caution; use MC.


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## Cl906um (Jul 21, 2012)

Quit spending a dime to save a nickel. Do it right the first time.inspector is right.


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## Peter Goldwing (Sep 23, 2011)

Lets say the A/C supply is on one end of a finished hallway and the return on the other end. Is this hallway a plenum ? If so then no lighting fixture would be allowed in the hallway
My previous question is pretty much the same except we are talking up and down on return and supply.


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## splatz (May 23, 2015)

dinlugoj said:


> Lets say the A/C supply is on one end of a finished hallway and the return on the other end. Is this hallway a plenum ? If so then no lighting fixture would be allowed in the hallway
> My previous question is pretty much the same except we are talking up and down on return and supply.


Good luck with that airtight reasoning bro LOL


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## Peter Goldwing (Sep 23, 2011)

Also , romex wire is allowed to pass thru an air return bay. My wiring will not be longer then 16 inch. Now what?


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## MechanicalDVR (Dec 29, 2007)

dinlugoj said:


> Also , romex wire is allowed to pass thru an air return bay. My wiring will not be longer then 16 inch. Now what?


NO, romex is not allowed to pass through any return plenum.


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## cabletie (Feb 12, 2011)

I am reading it as all ceilings are hard, just different levels or dropped. I would say it's not just the wiring method but the lights as well. 

Have the carpenter box out for the high hats and run the Romex perpendicular to the joists per the exception, or run EMT to the lights. If it is a plenum, and not just a space used for environmental air.


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## TGGT (Oct 28, 2012)

Do it right and chalk it up to a lesson learned and bid/plan appropriately next time.


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## Signal1 (Feb 10, 2016)

dinlugoj said:


> Also , romex wire is allowed to pass thru an air return bay. My wiring will not be longer then 16 inch. Now what?


Dude, your question has been answered 8 times.


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## Peter Goldwing (Sep 23, 2011)

Dude Im no here for any answer, just for the correct one. When the AC guy cuts the bottom space between 2 studs , puts a block at 7 ft high and a sheet metal with a rectangular opening it is a return air. YOU ARE ALLOWED to run wires in this area perpendicular to the studs. You cannot install a switch or receptacle in there or run wires longitudinally. PS Problem was fixed by scraping the high hats and installing two sconces on the wall


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## Peter Goldwing (Sep 23, 2011)

cabletie said:


> I am reading it as all ceilings are hard, just different levels or dropped. I would say it's not just the wiring method but the lights as well.
> 
> Have the carpenter box out for the high hats and run the Romex perpendicular to the joists per the exception, or run EMT to the lights. If it is a plenum, and not just a space used for environmental air.


Thats exactly what I think it is


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## MechanicalDVR (Dec 29, 2007)

dinlugoj said:


> Dude Im no here for any answer, just for the correct one. When the AC guy cuts the bottom space between 2 studs , puts a block at 7 ft high and a sheet metal with a rectangular opening it is a return air. YOU ARE ALLOWED to run wires in this area perpendicular to the studs. You cannot install a switch or receptacle in there or run wires longitudinally. PS Problem was fixed by scraping the high hats and installing two sconces on the wall


Maybe if you are dealing with a blind inspector or handing him a fat envelope. But in the real world that blocking makes the space a return duct. The same way you can't pass romex through a sheetmetal duct you can't pass through that return duct space.


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## Peter Goldwing (Sep 23, 2011)

Make yourself a favor if you are wiring houses. Find out that you ARE ALLOWED to run wires perpendicular to those studs. It may save you money on the long run. I wired hundreds of houses this way. Im not going to argue with you any further. Do it your way


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## MechanicalDVR (Dec 29, 2007)

dinlugoj said:


> Make yourself a favor if you are wiring houses. Find out that you ARE ALLOWED to run wires perpendicular to those studs. It may save you money on the long run. I wired hundreds of houses this way. Im not going to argue with you any further. Do it your way


I've wired more commercial fits out in NJ than you have houses and the rules don't change as far as I know.


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## Peter Goldwing (Sep 23, 2011)

See NEC Section 300.22(C),
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(C) 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.


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## Signal1 (Feb 10, 2016)

> Lets say the A/C supply is on one end of a finished hallway and the return on the other end. Is this hallway a plenum ? If so then no lighting fixture would be allowed in the hallway
> My previous question is pretty much the same except we are talking up and down on return and supply.


300.22(C) this section shall not apply to habitable rooms or areas of buildings...



> Dude Im no here for any answer, just for the correct one. When the AC guy cuts the bottom space between 2 studs , puts a block at 7 ft high and a sheet metal with a rectangular opening it is a return air. YOU ARE ALLOWED to run wires in this area perpendicular to the studs. You cannot install a switch or receptacle in there or run wires longitudinally. PS Problem was fixed by scraping the high hats and installing two sconces on the wall


This in no way describes your OP



> See NEC Section 300.22(C),
> 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.


This exception does not apply to your situation at all.

*300.22(C) Other Spaces Used for Environmental Air(Plenums) * describes the situation you have there, so the wiring methods in 300.22(C)1 including MI,MC,AC, or other cable specifically listed for use within an air handling space. Or other cables in conduit, EMT or flexible metal conduit.

In this case the inspector was correct. A little flex was all you needed.

I'm glad you resolved your issue.


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