Getting a better understanding of NM allowed in commercial settings...

Status
Not open for further replies.
S

sw_ross

Senior Member
Location
NoDak
I've done some reading through the search function of previous discussions about the use of NM in a commercial setting.
For me it's always been a grey area of having confidence in my understanding.

I am about to start a renovation of the lobby area of a small motel. It was probably built in the 70's. Typical "row" style mom and pop type motel. It's a single level, slab on grade with typical wood construction (wood trusses and 2x wood walls). It does have a sprinkler system throughout the motel that includes the lobby area and all the rooms. There's probably 20 guest rooms that extend in a row down from the lobby, all having exterior entry doors (no hallway). The whole complex shares the same roofline and I'm assuming has an open attic space that encompasses the whole complex (although I haven't yet confirmed that).

Currently it seems the original wiring is EMT. As we start demo I'll have a better look at things.
There currently isn't a drop ceiling. I understand NM isn't allowed in drop ceilings, and I will respect that requirement in areas that drop ceilings are added. Otherwise I'm not seeing anything that keeps me from using NM.

Based off my description can you give me input for things I should be aware of, or concerns I should look into further?
I'll be calling the AHJ for feedback before starting to run any new wire.

Thanks
 
I typically try to use the same wiring method when involved in renovations, unless it's not code compliant anymore or just doesn't make sense to so.
I have used NM in some commercial settings.
Definitely check in with the AHJ.
Be aware NM is not allowed in drop ceilings if they are used as a plenum.
Be aware of places of assembly if any.
 
We used to do a lot of Extended Stay hotels, and a lot of them are wired in nm cable, one municipality balked at it, but allowed it once they found out it is considered “transit housing” I have always thought if it was a “fire rated” structure, nm could not be used. I could be wrong. Since it is sprinklered, I would say it was fire rated. The assisted living facilities we done were all mc cable, but could be local code.
 
NM is not allowed in suspended ceiling space at all, except in dwelling units. (Have no idea the reason)

In other than dwellings it must be behind at least a 15 minute finish IIRC, so as a general rule if it will be exposed it probably isn't allowed in that particular location. You can run NM cable in walls/ceilings and transition to other wiring methods where it will be exposed.

It can't be used in art 517 or 518 applications.
 
All rooms, including lobby/office area have PTAC units so the "shared" attic space is not plenum.

I'm assuming a firewall rating between rooms and lobby/office space, but doubt that includes a separation in the attic that is fire rated if that applies or is important?
 
sw_ross said:
All rooms, including lobby/office area have PTAC units so the "shared" attic space is not plenum.

I'm assuming a firewall rating between rooms and lobby/office space, but doubt that includes a separation in the attic that is fire rated if that applies or is important?
Click to expand...
NEC has no fire wall rating requirement for this. Other codes may still require such in your application though. I could see the corridors require 1 hour finish (is an egress path) but maybe lesser rating being minimum requirement between other rooms. That still wouldn't mean you can't run NM for wiring method to corridor items based on NEC only.
 
Sorry,
I believe NM is allowed in dropped ceilings in Massachusetts under the amendments 334.12(A) (2)
Anyone familiar with Massachusetts code feel free to correct me if I'm wrong.
 
Based on 334.10 and its reference to annex E (construction types), I look at Annex E and my eyes glaze over...

I wish i could find a basic discussion about construction types (with examples) and how it applies to wiring methods (Chapter 3).
 
sw_ross said:
Based on 334.10 and its reference to annex E (construction types), I look at Annex E and my eyes glaze over...

I wish i could find a basic discussion about construction types (with examples) and how it applies to wiring methods (Chapter 3).
Click to expand...
If trades or maint can excess an area such as an attic space than the cable is exposed and subject to being damaged.

As far as construction types,rule out 1 and 2 you would not expect to see wood studs and other ignitable building materials

A building official years ago told me if you see lumber building materials you’re not in type 1or 2
 
kwired said:
NM is not allowed in suspended ceiling space at all, except in dwelling units. (Have no idea the reason)

In other than dwellings it must be behind at least a 15 minute finish IIRC, so as a general rule if it will be exposed it probably isn't allowed in that particular location. You can run NM cable in walls/ceilings and transition to other wiring methods where it will be exposed.

It can't be used in art 517 or 518 applications.
Click to expand...
There are a some states in NE that now allow for NM in suspended ceilings in some cases. NH, ME and VT are a few that may, I know that NH does.
 
hillbilly1 said:
Probably due to basement finishes using suspended ceilings.
Click to expand...
Yes they often do, but why is it ok in a dwelling, where people commonly spend a significant amount of time sleeping, but is most definitely going to kill people if in a non dwelling?
 
kwired said:
Yes they often do, but why is it ok in a dwelling, where people commonly spend a significant amount of time sleeping, but is most definitely going to kill people if in a non dwelling?
Click to expand...
Probably a question of money, you build a house, wire it in nm, then the owner decides to put a drop ceiling in the basement. Then all of the wiring exposed in the basement ceiling would have to be changed. Most of the code is written by manufactures, so that probably had something to do with it. You would be hard pressed to make a case that NM above a suspended ceiling is hazardous.
 
hillbilly1 said:
Probably a question of money, you build a house, wire it in nm, then the owner decides to put a drop ceiling in the basement. Then all of the wiring exposed in the basement ceiling would have to be changed. Most of the code is written by manufactures, so that probably had something to do with it. You would be hard pressed to make a case that NM above a suspended ceiling is hazardous.
Click to expand...
Money doesn't really matter to most NEC articles, again why is NM safe in our houses, where we sleep, yet in some non dwelling applications it is a hazard and can not be used?
 
kwired said:
Money doesn't really matter to most NEC articles, again why is NM safe in our houses, where we sleep, yet in some non dwelling applications it is a hazard and can not be used?
Click to expand...
Tell that to Eaton who pushed through the arc fault requirements. What do you do when nobody wants your product? You force them to buy it. $$$$
 
hillbilly1 said:
Tell that to Eaton who pushed through the arc fault requirements. What do you do when nobody wants your product? You force them to buy it. $$$$
Click to expand...
Money helped drive Eaton to lobby their product, which they did so in the name of safety, but money wasn't the reason the CMP made any decisions on what to put into code.

My point is just because something seems expensive is not a reason to the CMP to make decision. Statistics on saving lives, even if exaggerated, is more helpful at getting something you want into code. Lately there doesn't even seem to need to be statistics, just a suggestion that something will be safer. Look at recent GFCI rules changes, lots of the new requirements involve things that haven't much for history on being shock hazards.
 
kwired said:
NM is not allowed in suspended ceiling space at all, except in dwelling units. (Have no idea the reason) ....
Click to expand...
It was just part of the give and take when the 3 story limitation was removed from the code. Some restrictions had to remain in order to get the 2/3s majority vote of the code making panel members to remove the 3 story limit.
 
hillbilly1 said:
Tell that to Eaton who pushed through the arc fault requirements. What do you do when nobody wants your product? You force them to buy it. $$$$
Click to expand...
As I recall, there was no support from Eaton for the original AFCI proposals as they did not have a product ready to market at the time the original proposals were made.
 
don_resqcapt19 said:
As I recall, there was no support from Eaton for the original AFCI proposals as they did not have a product ready to market at the time the original proposals were made.
Click to expand...
From what I was told in CE classes, Eaton was the only ones that had the technology, and was making it for the rest of the manufactures until they got their products out. Wouldn’t be the first time I was given bad information from the professionals. LOL!
 
Status
Not open for further replies.
Top