Nm-B Question

[Pep]

Hello guys,

I am new here and wanted to see of you guys can help me clarify a question on NM-B wiring.

I am estimating a 5 story apartment building and I wanted to know if NM-B was allowed for general circuits INSIDE the unit. I got the idea from a remodel we did in a penthouse of a 51 story building. I went out to see the job and saw that all the 15 and 20 branch circuits were done in NM-B.

Now 334.10 says that in type III building it is allowed. This is a tunnel form job, so all the walls and ceilings will be concrete and the exterior walls will be CMB. Concrete has, I believe, a 2 hour fire rating.


So, is there a code section that I am overlooking. It has been a while since I work the field and use the code mainly for motor calculations and 310-16 and 310-15(b)(6).

Thanks for the help.

 

[mcclary's electrical]

Local rules will apply. If it's a place of assembly that holds more than 100 peolpe,then you can't use NM. Some local codes rule out anything over 3 stories, others anything over 5, others not at all. Keep in mind that NM is not allowed exposed ANYWHERE in commercial work. All NM must be concealed in a floor, wall, or ceiling with at least a 15 minute fire rating (Examples of such construction in NFPA 5000)

 

[lakee911]

Code is kind of vague (in my opinion) where it can be exposed, where can it other places?

 

[mcclary's electrical]

Code is kind of vague (in my opinion) where it can be exposed, where can it other places?

It doesn't seem vague. It's not allowed to be exposed ANYWHERE in commercial work

 

[Pep]

Local rules will apply. If it's a place of assembly that holds more than 100 peolpe,then you can't use NM. Some local codes rule out anything over 3 stories, others anything over 5, others not at all. Keep in mind that NM is not allowed exposed ANYWHERE in commercial work. All NM must be concealed in a floor, wall, or ceiling with at least a 15 minute fire rating (Examples of such construction in NFPA 5000)

I know the 100 person place of assembly. I use it to run NM in clubhouses. But I think the Code is vague in that the individual units will obviously not be a place of assembly for more than the average 2 persons per bedroom.

The work is in Miami-Dade county and it follows the FBC and the electrical portion refers back to the NEC. So, that is my dilemma. I understand that NM can not be embedded in concrete and all the other requirements. But, this one is really frustrating. Every electrician I speak to at the office has an argument in the opposite direction.

 

[lakee911]

It doesn't seem vague. It's not allowed to be exposed ANYWHERE in commercial work

Sorry, I meant in general...like where can be in residential?

 

[jaylectricity]

Sorry, I meant in general...like where can be in residential?

In an unfinished basement, you can staple the wires to the framing or joists and it will be exposed unless you sheetrock the walls. That's one example that I'm sure of.

 

[e57]

I know the 100 person place of assembly. I use it to run NM in clubhouses. But I think the Code is vague in that the individual units will obviously not be a place of assembly for more than the average 2 persons per bedroom.

A few places I work at around here have buildings of mixed use. e.g. a first story of commercial office/retail with a concrete deck above - then above - 3-4 stories of residential. Sometimes a commercial garage and retail - even a theater - and residential adjacent, or above. They get wired in appropriate methods for what often gets called an 'envelope'... Sometimes - One part of the building is one building type, the other - another building type. Granted this type of thing is not common everywhere.... And is outside of the NEC... Now granted - you could wire a 50 story single family home in NM - the 'family' could be 200 people and a dining room for them all to eat in.... But here if the building were zoned and allocated to be multi-family etc. - there would be no way in hell....

So you really need to check with the building dept in the place of the project to really make sure... For that matter there may be a building association with their own set of rules too.

 

[George Stolz]

If it's a place of assembly that holds more than 100 peolpe,then you can't use NM.

I think the OP was fairly specific that he was talking about the inside of an apartment unit.

It's not allowed to be exposed ANYWHERE in commercial work

Code reference, please?

So you really need to check with the building dept...

Agreed.

 

[mcclary's electrical]

I think the OP was fairly specific that he was talking about the inside of an apartment unit.


Code reference, please?






334.10 (3)

cut and dry

 

[George Stolz]

My mistake, I thought you were saying it was prohibited to be exposed in an apartment building. Since the OP was talking about an apartment building, I was locked into that mindset. Sorry about that.

 

[mcclary's electrical]

My mistake, I thought you were saying it was prohibited to be exposed in an apartment building. Since the OP was talking about an apartment building, I was locked into that mindset. Sorry about that.

No need to apologize,,,,I was locked in the mindset and forgot about him saying apartment (hence my place of assembly remark)



We all have slower baud rates from time to time:grin:

 

[Pep]

Guys,

First of all, I want to thank all you guys for the responses. You all know your stuff.

I have read 334.10 (3), and that is what has me questioning this. I BELIEVE it is allowed for interior of the residential, or living, quarters. The breezeways, exercise rooms, etc will be in smurf through slab and EMT and MC where allowed respectively.


But the interior of the units is what has me rattled. Does 334.10 (3) allow for the use of NM? Is this the code article I have to use for my argument with the AHJ? I just don't want to go in there and have them point of something in the code that may me obvious that I can't seem to find.

Again, thanks for the help. This place seems to be a treasure chest of information.