NM cable into panel

N

nizak

Senior Member
I’m doing an addition to a commercial building.
The construction type allows me to use NM-B wiring.

The existing ( 40 years old) mechanical room ( ceiling and walls finished drywall) has the NM-B coming through the drywall ceiling and stapled to the plywood backer that the panel is mounted on in the same manner a new residential build would be done.

Can my newly installed circuits terminate the same way or do they need to be transitioned to a metal cable , or sleeved where they come down the wall approximately 3’ before entering the panel?

Thanks
 
334.10 - Uses permitted -
1 & 2 - dwelling (does not apply)
3 - Other structures permitted to ge of Tyeps III, IV, and V constrcution. Cables shall be concealed within walls, floors, or ceilings that provide a thermal barrier of material that has at least a 15-minute finish rating as identified in listings of fire-rated assemblies.
4 - cable trays in structures permitted to be types III, IV, or V where cables are identified for the use.
5 - types I and II construction where installed within raceways permitted to be installed in Types I and II constrcution.

so, one must maintain a 15-minute fire rating, period. one cannot leave fully-enclosed space of at least 1/2" drywall on fully enclosed stud spaces. this means, no metal studs with holes punched in them. and any holes in the wood studs, must be sealed back up, in order to maintain 15-minute rating.

also, 334.12(A)(2) USES NOT PERMITTED - Exposed within a dropped or suspended ceili=g cavity in other than one and two-family and multifamily dwellings.

so, cannot have NM cable above t-bar ceilings in non-dwelling.

as soon as NM comes out of the drywall, it is no longer within 15-minute fire rating. this makes it a NO-GO unless you come out of the drywall into the back of some kind of enclosure, and then sleeve them in conduit to the panel. even then, you must seal hole back into drywall, to maintain 15-minute rating inside the stud cavity.

generally, NM in a non-dwelling is frowned upon, in the professional community. MC cable is preferred.
 
Master Nater said:
334.10 - Uses permitted -
1 & 2 - dwelling (does not apply)
3 - Other structures permitted to ge of Tyeps III, IV, and V constrcution. Cables shall be concealed within walls, floors, or ceilings that provide a thermal barrier of material that has at least a 15-minute finish rating as identified in listings of fire-rated assemblies.
4 - cable trays in structures permitted to be types III, IV, or V where cables are identified for the use.
5 - types I and II construction where installed within raceways permitted to be installed in Types I and II constrcution.

so, one must maintain a 15-minute fire rating, period. one cannot leave fully-enclosed space of at least 1/2" drywall on fully enclosed stud spaces. this means, no metal studs with holes punched in them. and any holes in the wood studs, must be sealed back up, in order to maintain 15-minute rating.

also, 334.12(A)(2) USES NOT PERMITTED - Exposed within a dropped or suspended ceili=g cavity in other than one and two-family and multifamily dwellings.

so, cannot have NM cable above t-bar ceilings in non-dwelling.

as soon as NM comes out of the drywall, it is no longer within 15-minute fire rating. this makes it a NO-GO unless you come out of the drywall into the back of some kind of enclosure, and then sleeve them in conduit to the panel. even then, you must seal hole back into drywall, to maintain 15-minute rating inside the stud cavity.

generally, NM in a non-dwelling is frowned upon, in the professional community. MC cable is preferred.
Click to expand...
Thank you for the information.
 
nizak said:
I’m doing an addition to a commercial building.
The construction type allows me to use NM-B wiring.
Click to expand...
I always double check that i have it in writing, I have had some confuse type III with type II-B which is still a type II of course.
And if I have to put all NM in a raceway I am better off with MC.
Also I have had article 518 complicate things, people splitting hairs what is a portion is assembly occupancy and whats not.
If its anything on the list in Article 518.2 I submit a RFI, to clarify if builder wants all new wiring to be a method that 'qualifies as an equipment ground' as per 518.4.
In all practicality of running a commercial job where romex is allowed in this wall but not that that wall (or ceiling), I'd rather just use MC for the whole job. One mistake where they used NM because they ran out of MC and you eat into the savings of NM cable.
 
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