Arnored Cable

[mrmax1200]

We recently had the pleasure of taking on a project which needed to have the Bx cable installed in cut grooves of brick walls, with plaster skim coat finish, of renovated condo units.
These cables will run from box to box for receptacles and switches.
The architect elected not to finish the walls in dry wall,but to keep the original look.
To do this we saw cut grooves wide enough and deep enough just to get a skim coat of plaster over it.
Keep in mind we can not cut the grooves much deeper than the diameter of the cable, without compromising the structure of the wall !
We failed the rough inspection, because the inspector wants the cable at least 1 1/4 deep from the front part of the cable.
He sited me articles 300-4 & 333 of the NEC.
Again, keep in mind, no covering on the walls such as paneling,drywall,carpeting etc. will be on the walls. only plater and paint !

 

[iwire]

Re: Arnored Cable

IMO the inspector is correct in regards to 300.4(E)

(E) Cables and Raceways Installed in Shallow Grooves. Cable- or raceway-type wiring methods installed in a groove, to be covered by wallboard, siding, paneling, carpeting, or similar finish, shall be protected by 1.6 mm (1/16 in.) thick steel plate, sleeve, or equivalent or by not less than 32 mm (11/4 in.) free space for the full length of the groove in which the cable or raceway is installed.

Exception: Steel plates, sleeves, or the equivalent shall not be required to protect rigid metal conduit, intermediate metal conduit, rigid nonmetallic conduit, or electrical metallic tubing.

You will either have to run a metal raceway (a little late now) or protect the cable with 1.6 mm (1/16 in.) thick steel plate, sleeve, or equivalent.

333 does not exist in the 2002 NEC, do you have more info on that?

 

[petersonra]

Re: Arnored Cable

how hard is it to install the plates?

 

[apauling]

Re: Arnored Cable

It seems that it is actually legal to use the outer finished wiremold sleeve (without the sliding insert) to protect romex in this situation. getting plates to adhere may be a problem. see if there is a wiremold sleeve large enough to cover the bx.

paul

 

[al hildenbrand]

Re: Arnored Cable

I'm confused. . .how does 320.10(4) not apply?

II. Installation
320.10 Uses Permitted.

Where not subject to physical damage, Type AC cable shall be permitted as follows: </font>

• <font size="2" face="Verdana, Helvetica, sans-serif">(4) Embedded in plaster finish on brick or other masonry, except in damp or wet locations.</font>

<font size="2" face="Verdana, Helvetica, sans-serif">

It seems to me that 300.4(E) includes wall covering with "wallboard, siding, paneling, carpeting, or similar finish"

Is plaster in a groove different than when it is applied to the surface of the brick? I don't think so.

The 300.4(E) catch phrase or similar finish seems to me is referring to sheets applied by fasteners, not trowels.

Edit typo - Al

[ January 15, 2005, 11:42 AM: Message edited by: al hildenbrand ]

 

[iwire]

Re: Arnored Cable

Al it does apply just like NM is allowed to run through studs, however if either of these methods are closer than 1.25" to the surface we have to follow 300.4(E) (or other sections in 300.4)

As far as the finish is it your argument that paint and compound protects the cable better than paneling?

[ January 15, 2005, 11:55 AM: Message edited by: iwire ]

 

[al hildenbrand]

Re: Arnored Cable

Bob,

320.15 Exposed Work.

Exposed runs of cable, except as provided in 300.11(A), shall closely follow the surface of the building finish or of running boards. Exposed runs shall also be permitted to be installed on the underside of joists where supported at each joist and located so as not to be subject to physical damage.

I can run the AC on the surface of the wall. . .right?

Or am I in need of coffee?

 

[pierre]

Re: Arnored Cable

Al
The problem that could arise if the AC is covered by only a 'skim' coat of plaster is a person could unknowingly drive a screw or other fastener through the armor without knowing the cable was there. Hence as Bob has said 1.25 inches from the cable sheath to the surface of the finish.

Pierre

 

[al hildenbrand]

Re: Arnored Cable

Pierre,

The problem I'm having with the language in 320 and 300.4 is that it seems I can run AC on the surface of a masonry wall and then plaster over it with plaster directly applied to the masonry. . .without nail plating - 320.10(4).

If that is so, then how is this plaster coating any different from the solution that mrmax1200 arrived at in his/er openning post? While the shallow groove is present, it is not for prep for the installation of wallboard, siding, paneling, carpeting, or similar finish, rather it is for plaster.

 

[al hildenbrand]

Re: Arnored Cable

And finally,

ARTICLE 300 Wiring Methods
I. General Requirements
300.1 Scope.
(A) All Wiring Installations. This article covers wiring methods for all wiring installations unless modified by other articles.

To me, 300.1(A) says Article 320.10(4) takes precedence over 300.4(E).

IMO mrmax1200's inspector got it wrong.

 

[kiloamp7]

Re: Arnored Cable

iwire - you asked - Art. 333 was "Armored Cable Type AC" (BX) for many, many years until 2002 NEC changed the article #.

 

[al hildenbrand]

Re: Arnored Cable

mrmax1200,

What Code cycle is the job under? 2002 or earlier?

 

[pierre]

Re: Arnored Cable

We are not saying that 320.10(4) does not apply, but when installing as per 320.10(4), we still need to apply 300.4(E). Cables and Raceways Installed in Shallow Grooves.

 

[al hildenbrand]

Re: Arnored Cable

Pierre,

Hypothetical. Using 320.10(4), can I plaster over AC that is closely following a brick wall surface? No shallow grove, the AC is on the brick surface. The plaster is ?" thick and the AC is 12/3.

 

[al hildenbrand]

Re: Arnored Cable

Pierre posted January 15, 2005 02:04 PM

The problem that could arise if the AC is covered by only a 'skim' coat of plaster is a person could unknowingly drive a screw or other fastener through the armor without knowing the cable was there.

The wall is brick, and the wall is not to be covered by wallboard, siding, paneling, carpeting, or similar finish {300.4(E)}. No screws or fasteners are going to be installed in order to "finish" the brick wall.

Bob,

iwire posted January 15, 2005 11:44 AM

As far as the finish is it your argument that paint and compound protects the cable better than paneling?

This brick wall is in a dwelling unit, not on a loading dock. IMO the AC is not exposed to physical damage on a brick wall that is part of an aesthetic of a dwelling unit. Skim coating with plaster is allowed by 320.10(4). Setting the AC in a groove and skim coating doesn't increase the exposure to fasteners that aren't being used to cover by wallboard, siding, paneling, carpeting, or similar finish {300.4(E)}.

Now, if the AC is run in a groove in the masonry where the kitchen cabinets are to be installed. . .you bet, nail plates are required.

But open dwelling brick wall. . .2002 300.1(A) and 320.10(4) are what apply.

 

[iwire]

Re: Arnored Cable

Al,

Bob,

This brick wall is in a dwelling unit, not on a loading dock. IMO the AC is not exposed to physical damage on a brick wall that is part of an aesthetic of a dwelling unit.

We will have to agree to disagree.

IMO once the cable is not in plain sight on the surface of the wall, as in covered with carpet, wall paper, paneling or a skim coat of plaster I believe it needs to be 1.25 back from the surface or protected by 1/16" of metal.

I look at this the same as Table 300.5 for underground installations.

You can run a raceway laying exposed on the surface of the earth, but if you chose to conceal it you must follow the depth requirements.

Look at 300.4(A)(1) & (2) both of those apply to all walls not just a wall where cabinets will be hung.

I have always assumed this was to keep the occupants from damaging cables if hanging pictures, or book shelves etc. on the wall at some point.

I believe 300.4(E) is in the code for the same reason.

 

[George Stolz]

Re: Arnored Cable

Originally posted by iwire:
IMO once the cable is not in plain sight on the surface of the wall, as in covered with carpet, wall paper, paneling or a skim coat of plaster I believe it needs to be 1.25 back from the surface or protected by 1/16" of metal.

IMO, I agree.

You can run a raceway laying exposed on the surface of the earth, but if you chose to conceal it you must follow the depth requirements.

Yes.

Look at 300.4(A)(1) & (2) both of those apply to all walls not just a wall where cabinets will be hung.

Bob, they make a distinction in construction types here that your conscience is ignoring. Your desire for a perfect installation is clouding your interpretation. 300.4(A) is distinctly titled "Cables and Raceways Through Wood Members." For the original poster's predicament, he can stop reading there. It doesn't exist, or at least in no way applies.

I have always assumed this was to keep the occupants from damaging cables if hanging pictures, or book shelves etc. on the wall at some point.

I believe 300.4(E) is in the code for the same reason.

I read your last post originally, Bob, and agreed with you. That's what I thought too. We were wrong.

Upon reading the code, 300.4(E) is where the installer must start reading. That is the method that he is using. I might not have seen the pattern if Al hadn't brought it up: all wall coverings they mention involve fasteners. If I were asked by a friend what I would do to disguise a long groove in a brick wall over a receptacle, I would suggest wallpaper. Drywall would be about fourth on the list. The CMP specifically left out any covering utilizing adhesives over fasteners.

Our belief about picture hanging injuring our installations is also tempered by one other thing. Drywallers use short screws. This can be monitored and controlled by a GC--the GC doesn't want a backcharge from the electrician because his drywallers used 3" screws. Where a homeowner can drive a nail and how long that nail will be is utterly out of control. If this were a concern of the CMP, NM cable would be illegal, IMO.

In addition, in order to mount a picture on a brick wall, an anchor would probably be installed. With the nature of plaster versus the nature of brick, even a blind man would probably notice the difference in texture, find it unsecure, and move to a more solid spot for his anchor.

 

[George Stolz]

Re: Arnored Cable

Here's an analogy:

POCO's around here generally run a tracer wire with their undergrounds so that they can be located prior to digging. There is a high level of safeguarding associated with this.

By NEC, we're required to mark our service trenches with flagging tape to draw attention to the service conductors once digging has begun. This is a medium level of safety (required by NEC-2005 300.5(D)(4)).

We're not required to flag our trenches for branch circuits and feeders, relying on the OCPD to act once the underground is damaged. This is about the lowest level of safety.

Personally, I flag my trenches for feeders and BC's underground. But it isn't required by the lowering degrees of safety associated with the varying levels of installation.

I have a profound respect for what you and others here have taught me, Bob. But I think you've got just cause to rethink your position.

Edit to add: Generally, in my limited experience, when NM cable is damaged by nails and screws driven by homeowners, the offending screw connects the hot and ground, or the ground and neutral. If AFCI's become required in more locations, they will trip on the ground-neutral fault. Weak statement, but I thought I'd throw it in there.

[ January 16, 2005, 12:55 PM: Message edited by: georgestolz ]

 

[iwire]

Re: Arnored Cable

Originally posted by georgestolz:

Look at 300.4(A)(1) & (2) both of those apply to all walls not just a wall where cabinets will be hung.

Bob, they make a distinction in construction types here that your conscience is ignoring. Your desire for a perfect installation is clouding your interpretation. 300.4(A) is distinctly titled "Cables and Raceways Through Wood Members." For the original poster's predicament, he can stop reading there. It doesn't exist, or at least in no way applies.

George I never said that 300.4(A)(1) & (2) apply to this installation I was just pointing out that in general the NEC requires at least 1.25" set back of wiring methods that are concealed and could be damaged by nails or screws.

I would have no problem with this AC cable run on the surface of a brick wall in plain view.

Once it is hidden IMO the 1.25" set back or metal protection is required.

 

[drg]

Re: Arnored Cable

I would have to agree with iwire on this also.