NMD in Drop Ceiling - Electrician Talk - Professional Electrical Contractors Forum

Brnolan1 · 04-03-2012, 01:10 AM

A customer wants to put in t-bar in his house. The current ceiling is drywall and he wants to suspend it from this. I am looking to run the NMD on the drywall with approved strapping. The only issue I see is getting the cable strapped within 300mm of the 2x4 drop in light fixture, as the drop is 600mm. Is the 2x4 fixture considered a box? Has anyone had any experience with NMD in T-Bar?

mr_electrician · 05-11-2012, 10:54 PM

Quote:

Originally Posted by Brnolan1

A customer wants to put in t-bar in his house. The current ceiling is drywall and he wants to suspend it from this. I am looking to run the NMD on the drywall with approved strapping. The only issue I see is getting the cable strapped within 300mm of the 2x4 drop in light fixture, as the drop is 600mm. Is the 2x4 fixture considered a box? Has anyone had any experience with NMD in T-Bar?

Could you not nail a vertical 2X4 to the floor joist to get you to within 300mm?

magneticpersona · 05-12-2012, 01:42 AM

I have a lot of experience with t-bar installation and I know exacly what you need to do with this. You need to secure your wire to the t-bar hanger and that should meet your requirement for the 300mm. You are not allowed to use nmd90 in plenum chambers (t-bar ceilings) as per code clearly stated at the begining of section 12. NMD90 is not FT4 rated, which is the main reason for this. Usually AC90 is used since it meets those requirements. You can then strap is easily with ty-wraps or metal string/wire.

If you didn't pull a permit, you can go ahead with your nmd90, but if you did pull a permit, i highly recommend you follow my advice or your inspector will fail you

Nigelforsythe · 05-12-2012, 11:22 AM

You can use nmd90 in t-bar ceilings as long as the ceiling space isn't plenum rated. If the ceiling space is used to transport air rather than ducts then you have to use an ft4 rated cable. Not all t-bar ceilings are considered plenums.

magneticpersona · 05-12-2012, 02:28 PM

while i agree not all drop ceilings are considered plenums, the inspectors still don't pass it in my area. Their logic is that if it could become a return air plenum that it must be wired with FT4 wires. This is especially true of any commercial installation i have ever done. When it comes to residential, who knows. All that mathers is if the inspector likes it or not, and here they don't

magneticpersona · 05-12-2012, 02:58 PM

here is proof that this is not allowed:

rule 2-126(b)(ii) appendix B

FT4 to be used in spaces between a floor and a ceiling or ceiling and a roof,that may be used in as a plenum (that means current or possible future installation) in buildings of combustible or non-combustible construction. Its against building code too.

mattwright999 · 05-12-2012, 03:37 PM

Quote:

Originally Posted by magneticpersona

here is proof that this is not allowed:

rule 2-126(b)(ii) appendix B

FT4 to be used in spaces between a floor and a ceiling or ceiling and a roof,that may be used in as a plenum (that means current or possible future installation) in buildings of combustible or non-combustible construction. Its against building code too.

CEC 2012
Section 0
Definitions
Page 9
Plenum

Where in the OP does it he state it may be used an a plenum? It sounds like the tbar is being mounted on top of an existing drywall ceiling

magneticpersona · 05-12-2012, 04:18 PM

His original post doesn't mention it will be used as a plenum, but the code rule above or the inspector doesnt care. All they care about is the "possibility of future use".

anyways to put this one to bed, talk to your local inspector and find their stance on this. My inspectors say no.

Rochsolid · 08-10-2012, 02:17 PM

Ac90 and kx clips

cdnelectrician · 08-10-2012, 09:08 PM

Quote:

Originally Posted by Brnolan1

A customer wants to put in t-bar in his house. The current ceiling is drywall and he wants to suspend it from this. I am looking to run the NMD on the drywall with approved strapping. The only issue I see is getting the cable strapped within 300mm of the 2x4 drop in light fixture, as the drop is 600mm. Is the 2x4 fixture considered a box? Has anyone had any experience with NMD in T-Bar?

I think you will be ok just dropping down to the fixture, 300mm is about 12 inches how exactly can you secure a cable in exactly 12 inches when you are using a 2 x 4 flourescent? I would strap the NM to the ceiling with 1 hole clips and drop straight down to the fixture, leave a neat loop at the fixture. If the inspector wants to be a **** then screw a tywrap mount to the top of the fixture and tywrap the cable to it.

farlsincharge · 08-10-2012, 09:33 PM

Quote:

Originally Posted by magneticpersona

His original post doesn't mention it will be used as a plenum, but the code rule above or the inspector doesnt care. All they care about is the "possibility of future use".

anyways to put this one to bed, talk to your local inspector and find their stance on this. My inspectors say no.

At what point do you tell the inspectors they are full of ****? This game they play lately is a bunch of bull and I tell them straight out.

I mean maybe we should bury the underground feeders 27' down and encase them in insulation and depleted uranium in case anyone ever installs a space shuttle launch pad in the backyard. The "what ifs" never end.

nmd in commercial is hack, resi is fine.

Aegis · 08-10-2012, 11:35 PM

I agree, don't play around with the inspectors. Find out first if it'll pass, if not ust run BX and everything will be fine.

Signalservice · 08-10-2012, 11:52 PM

Quote:

Originally Posted by farlsincharge

At what point do you tell the inspectors they are full of ****? This game they play lately is a bunch of bull and I tell them straight out.

I mean maybe we should bury the underground feeders 27' down and encase them in insulation and depleted uranium in case anyone ever installs a space shuttle launch pad in the backyard. The "what ifs" never end.

nmd in commercial is hack, resi is fine.

QAGuy · 08-11-2012, 04:06 AM

Why would you try to out smart the inspectors or tell them that you know better? If you simply do it right, you never have to worry about your install. It should be common sense to run Bx as it is safer and is not subject to discussion on whether it is allowed or not. Do it with integrity and dont deal in the Bs.

BBQ · 08-11-2012, 05:02 AM

Quote:

Originally Posted by farlsincharge

nmd in commercial is hack, resi is fine.

As long as you are paying the bills I will run conduit.

CanadianSparky · 08-11-2012, 11:17 AM

How could an inspector fail you on using NMD if it is not a plenum? If it is not designed as a plenum when the install was done and after finishing you did everything to code. He can not fail you if you followed code directly. I have done NMD in t-bar ceiling (resi) and have never had an inspector bitch. They just want to make sure the fixtures are supported. And if one did I would ask him for a code reference. No wonder these guys are so egotistical because people let them away with being the "what I say goes even if I'm wrong"

eddy current · 08-12-2012, 07:38 AM

Quote:

Originally Posted by farlsincharge

I mean maybe we should bury the underground feeders 27' down and encase them in insulation and depleted uranium in case anyone ever installs a space shuttle launch pad in the backyard. The "what ifs" never end.