Use of nm cable in dwelling garage

[electricmanscott]

For those of us in Massachusetts add exception 2 to 334.10(3) For detached buildings that are accessory structures to dwelling occupancies, type NM, type NMC, and type NMW cables shall be permitted to be used without concealment.

Thank you the the Mass Code making panel for being the voice of reason yet again.

 

[electricmanscott]

According to Mike Holts book "Understanding the NEC" basements, barns and cold storage warehouses are considered to be damp locations. .

But a garage is none of those. :smile:

 

[augie47]

By practice, the areas I'm familiar with have allowed NMB in a detached reisdential garage as long as it is run parallel to the framing members (following the surface)-where under 8 ft) or is protected.
The reasoning I was given was that this woudl be allowed in an attached garage and detaching the garage does not increase the hazrad.

as far as NMC is concerned, Southwire states the following on their website:
"UF-B can be used in applications permitted for NMC in Section 334.10(B) of the National Electrical Code."

 

[iwire]

By practice, the areas I'm familiar with have allowed NMB in a detached residential garage as long as it is run parallel to the framing members (following the surface)-where under 8 ft) or is protected.

How does that have to do with a 15 minute barrier that is now required?

 

[augie47]

How does that have to do with a 15 minute barrier that is now required?

They are considering the garage to be part of the one and two-family dwelling.
The barrier is not required there, is it ?

 

[Mike01]

something new

something new

So nm is not acceptable in a attached garage that is not finished based on the NEC. Wow learn something new every day.

 

[iwire]

They are considering the garage to be part of the one and two-family dwelling.
The barrier is not required there, is it ?

If the garage is detached there is no way it is a dwelling of any kind.:smile:

That is way MA made amendments.

 

[raider1]

How does that have to do with a 15 minute barrier that is now required?

I agree.

For what it is worth it appears that a couple of proposals to the 2011 NEC have been accepted that would change 334.10(1) to add "and their accessory structures" to one and two family dwellings.

Chris

 

[al hildenbrand]

For what it is worth it appears that a couple of proposals to the 2011 NEC have been accepted that would change 334.10(1) to add "and their accessory structures" to one and two family dwellings.

Given the history that I've experienced wiring dwelling attached and detached garages, where the only restriction on NM is that it closely follow the framing the quick acceptance of the addition of the clarifying text only makes sense.

7-77 Log #3789 NEC-P07 Final Action: Accept
(334.10(1))
_______________________________________________________________
Submitter: James Grant, Rochester, NH
Recommendation: Revise text to read as follows:

334.10 Uses Permitted.
Type NM, Type NMC, and Type NMS cables shall be permitted to be used in the following:
(1) One- and two-family dwellings and their accessory structures.

Substantiation: With the present language an attached garage could utilize NM as an exposed wiring method. A detached garage, three ft away from the main dwelling, could not utilize NM as an exposed wiring method. The use of these accessory structures that are incidental to a dwelling unit normally do not change whether it is or is not attached to the structure. The requirement to add a 15-minute rated thermal barrier for dwelling unit?s accessory structures is excessive.

Panel Meeting Action: Accept

Number Eligible to Vote: 14
Ballot Results: Affirmative: 13 Negative: 1

Explanation of Negative:
LA DART, S.: The panel should reject this proposal, or accept in principal, in part. It would be acceptable to add ?garages and storage sheds? to the text, but to allow Type NM cable to be installed in ?ALL? accessory buildings creates a safety issue. Some of the accessory buildings would include children?s playhouses, pool houses, game rooms, etc. The wiring method should be protected in these types of structures.

 

[augie47]

If the garage is detached there is no way it is a dwelling of any kind.:smile:

That is way MA made amendments.

in TN you might be suprised to what is used as a dwelling unit
such as my houseboat View attachment 3493

 

[realolman]

Given the history that I've experienced wiring dwelling attached and detached garages, where the only restriction on NM is that it closely follow the framing the quick acceptance of the addition of the clarifying text only makes sense.

7-77 Log #3789 NEC-P07 Final Action: Accept
(334.10(1))
__________________________________________________ _____________
Submitter: James Grant, Rochester, NH
Recommendation: Revise text to read as follows:

334.10 Uses Permitted.
Type NM, Type NMC, and Type NMS cables shall be permitted to be used in the following:
(1) One- and two-family dwellings and their accessory structures.

Substantiation: With the present language an attached garage could utilize NM as an exposed wiring method. A detached garage, three ft away from the main dwelling, could not utilize NM as an exposed wiring method. The use of these accessory structures that are incidental to a dwelling unit normally do not change whether it is or is not attached to the structure. The requirement to add a 15-minute rated thermal barrier for dwelling unit’s accessory structures is excessive.

Panel Meeting Action: Accept

Number Eligible to Vote: 14
Ballot Results: Affirmative: 13 Negative

I always need a brick wall to fall on me.... does your post mean what I think it means: that it is OK to wire a residential garage, detatched or attatched, with exposed NM?

 

[raider1]

I always need a brick wall to fall on me.... does your post mean what I think it means: that it is OK to wire a residential garage, detatched or attatched, with exposed NM?

It means that the 2011 NEC will more than likely permit NM cable to be installed in a detached garage accessory to a single or two family dwelling without the NM cable needing to be concealed within finish material with a 15 minute finish rating.

Chris

 

[realolman]

SO the log of the submission is for the next code ... not a record of a past code?

And why the heck do they keep mentioning NMC... why don't they give it up?

 

[iwire]

Given the history that I've experienced wiring dwelling attached and detached garages, where the only restriction on NM is that it closely follow the framing the quick acceptance of the addition of the clarifying text only makes sense.

I agree 100%. :smile:

 

[LarryFine]

And why the heck do they keep mentioning NMC... why don't they give it up?

Maybe they're using NMC to mean Non-Metallic Cable, not Corrosive.

 

[Dennis Alwon]

I always need a brick wall to fall on me.... does your post mean what I think it means: that it is OK to wire a residential garage, detatched or attatched, with exposed NM?

As long as it is not subject to damage, etc. Some will argue the detached garage but around here the detached garage is looked at as a residential building. Hence the change in the 2011 code to clarify this issue. Technically you could get red tagged for exposed nm in a detached garage.

334.15 Exposed Work.
In exposed work, except as provided in 300.11(A), cable shall be installed as specified in 334.15(A) through (C).
(A) To Follow Surface. Cable shall closely follow the surface of the building finish or of running boards.
(B) Protection from Physical Damage. Cable shall be protected from physical damage where necessary by rigid metal conduit, intermediate metal conduit, electrical metallic tubing, Schedule 80 PVC conduit, or other approved means. Where passing through a floor, the cable shall be enclosed in rigid metal conduit, intermediate metal conduit, electrical metallic tubing, Schedule 80 PVC conduit, or other approved means extending at least 150 mm (6 in.) above the floor.
Type NMC cable installed in shallow chases or grooves in masonry, concrete, or adobe, shall be protected in accordance with the requirements in 300.4(F) and covered with plaster, adobe, or similar finish.

 

[Dennis Alwon]

Maybe they're using NMC to mean Non-Metallic Cable, not Corrosive.

I doubt it. Check out below.

334.116 Sheath.
The outer sheath of nonmetallic-sheathed cable shall comply with 334.116(A), (B), and (C).
(A) Type NM. The overall covering shall be flame retardant and moisture resistant.
(B) Type NMC. The overall covering shall be flame retardant, moisture resistant, fungus resistant, and corrosion resistant.
(C) Type NMS. The overall covering shall be flame retardant and moisture resistant. The sheath shall be applied so as to separate the power conductors from the communications conductors.

 

[electricmanscott]

As long as it is not subject to damage, etc. Some will argue the detached garage but around here the detached garage is looked at as a residential building. Hence the change in the 2011 code to clarify this issue. Technically you could get red tagged for exposed nm in a detached garage.

Are you saying this in reference to the current code?

 

[electricmanscott]

Kind of funny the OP never actually mentioned a detached garage. :grin:

 

[PetrosA]

But not all basements are considered a damp location. Mike may make this statement simply because the NEC also makes that statement in the definition:

Location, Damp. Locations protected from weather and
not subject to saturation with water or other liquids but
subject to moderate degrees of moisture. Examples of such
locations include partially protected locations under canopies,
marquees, roofed open porches, and like locations,
and interior locations subject to moderate degrees of moisture,
such as some basements, some barns, and some cold storage
warehouses.

This simply can't be a broad assumption, this is why the electrical inspector has to interpret onsite the issues. I have a basement that has never had any moisture within it and I have a detached garage that has never had any signs of moisture within it. Lets remember the question is being posed about Garages and this is not a listed location in Mike Holts statement and they use such as to give examples not mandates.

As far as those "some" locations, it would be appropriate if the NEC defined a lot more detail such as what percentage of humidity for how long, at what temperature, where the measurement is taken, etc. "Moderate degrees" can mean a lot of different things to different inspectors, especially since humidity is measured in percent

But seriously, is a basement a damp location when you feel a chill walking into it, or when you see the walls are at the dew point and water is beading on them in the summertime, or when the concrete floor stains after a rain from ground seepage or if it has a dirt floor? There are a lot of situations that need to be clarified.