Aegis

We're in a commercial building and they're building walls with wood studs. They're also putting a drop ceiling (t-bar) in. Can you run non metallic sheathed cable above a drop ceiling?

EC2253

If you are asking about code No see 334.12

Aegis

I am asking about code yes CEC

arni19

The wire method used is going to depend on the materil used to build the outside walls of the building. Combustible or non combistible. Then choose your wire. Also dont forget the ft4 requirements if the dropped ceiling becomes a plenum.

Aegis

The building is non-combustible. Inside is a small area that's built with wood studs. I know I can use Romex in the studs and BX everywhere else. If the return air is all in closed ducts above the t-bar would It then be ok?

arni19

Yeah , you should be fine.

The_Modifier

Yes, most A&W's are done that way. Just finishing one up near Ottawa.

Aegis

Thanks guys. Is this a mix of CEC and building code?

The_Modifier

it's above 3 feet and doesn't need mechanical protection. If it's wood construction NMD90 is permissible as per electrical code.

xlink

Above the drop ceiling is okay if it isn't a return air. 12-010, 2-126 and Appendix B 2-126. You need FT4 rating in a return air and NMD is FT1 or FT2.

B4T

Good to see you guys are not following the craziness we have down here about NM above suspended ceilings in commercial buildings..

But the real insanity test is if your code allows NM in a wet location..

Example would be NM sleeved in conduit on the outside of a house to feed an AC unit..

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crosport

Our code allows only NMWU not NMD to be used outside.Inside a conduit exposed to the weather is considered a wet location.Seal tite or teck from the w.p. disconnect is typically used in these situations.

magneticpersona

In BC, the fire code requires a FT4 rating for any wiring in plenum (drop ceilings) in commercial installations. This means no loomex, and your closest FT4 equivalent is Ac90 for normal voltages.

Nigelforsythe

Not all t-bar ceilings are considered plenums. If the ceiling is used to transport air rather than using ducts then you have to go with ft4 rated cables. I've only ran into a few in my area that were actually considered plenums. As long as it's wood framed you're usually okay to go with NMD.

magneticpersona

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

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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.

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xlink

That's an unreasonable interpretation of that statement.

I would have thought a reasonable inspector would first look at the space to determine if it "may be used" as a plenum. If there are no return air ducts connected to the space, a reasonable person would conclude that it certainly can't used as a plenum, so it doesn't fall into the scope of a space that "may be used" as a plenum.

In any event, although Appendix B is a good guide, it isn't code. See the note under the heading.

Your inspectors would have a better argument if the National Building Code said that spaces that aren't plenums are subject to the same rules as plenums, but until I see that, if it isn't a plenum, it simply isn't a plenum.

Thankfully, such obscure interpretations are restricted to the island.

mattwright999

edit: two of the same thread??

NMD in Drop Ceiling