ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat
Recent Posts
Increasing demand factors in residential
by tortuga - 03/28/24 05:57 PM
Portable generator question
by Steve Miller - 03/19/24 08:50 PM
Do we need grounding?
by NORCAL - 03/19/24 05:11 PM
240V only in a home and NEC?
by dsk - 03/19/24 06:33 AM
Cordless Tools: The Obvious Question
by renosteinke - 03/14/24 08:05 PM
New in the Gallery:
This is a new one
This is a new one
by timmp, September 24
Few pics I found
Few pics I found
by timmp, August 15
Who's Online Now
0 members (), 265 guests, and 15 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Page 1 of 2 1 2
#100339 11/13/06 08:50 PM
Joined: Jul 2002
Posts: 103
J
jes Offline OP
Member
Maybe someone else has seen this. Buddy calls me up and says he just encountered a crew mounting boxes and securing NM cable at an apartment complex job with that spray/expand foam you get at the home center for filling cracks. Did the whole job that way. They were incredulous (followed by belligerant) that he wouldn't accept it. I put together a list of Code sections but has anyone got any suggestions?

Stay up to Code with the Latest NEC:


>> 2023 NEC & Related Reference & Exam Prep
2023 NEC & Related Reference & Study Guides

Pass Your Exam the FIRST TIME with the Latest NEC & Exam Prep

>> 2020 NEC & Related Reference & Study Guides
 

#100340 11/13/06 09:41 PM
Joined: Oct 2002
Posts: 482
Z
Member
Unbelievable...Almost.

I have never heard of a foam designed for, tested for, or listed for the securing of ANYTHING electrical. It may exist, but not in my world.

Read through all the NEC codes about proper mounting and retention, and you'll find a lot of "designed for...", "listed for the use as...", etc.

If anyone knows an inspector that would pass such a thing, I owe you a cold one.

#100341 11/13/06 10:48 PM
Joined: Jul 2002
Posts: 717
M
Member
I haven't wired one, but I have asked about it, and it is pretty much my understanding that that is exactly how the cables are secured in those new concrete and foam panel houses. And they have been passing inspections all over the place. But where is a code that allows this method? Or better yet, where is the code that does not allow it?

#100342 11/13/06 11:38 PM
Joined: Mar 2004
Posts: 814
B
Member
I have not seen it used in conventional construction, but in mud adobe it is used here all the time and passed all the time. There isn't really a better way to secure boxes in mud adobe.

#100343 11/14/06 06:20 AM
Joined: Jan 2003
Posts: 4,391
I
Moderator
I don't see anything in the NEC that would prohibit this.


Bob Badger
Construction & Maintenance Electrician
Massachusetts
#100344 11/14/06 10:33 AM
Joined: Oct 2002
Posts: 482
Z
Member
Looks like I'm going to have quite a bar tab.

I'm still sceptical, but in concrete, this sounds plausable. I hadn't thought of that. However, I've always piped (PVC) when working in block or concrete.

Is there a specific product designed as an adhesive? Also, the product would have to be inert (completely) or you would risk reaction with the NM jacket.

My other concern would be replacement, say, if someone drilled through some NM in the wall. Now that the cell is full of foam, the cap would have to be removed and the foam dug out, etc. If the cap is inaccessable, we're now busting out concrete or block...not good planning.

I still can't see myself using this method. It just doesn't seem right.

Happy hour, anyone?

#100345 11/14/06 07:01 PM
Joined: Jan 2001
Posts: 1,044
Tom Offline
Member
The securing & supporting is covered in 334.30 and I see nothing there that specifically allows this type of installation.

However, an inspector can accept other methods (90.4 second paragraph). If I was inspecting, I would want some substantiation that the foam would not harm the cable (110.11).


Few things are harder to put up with than the annoyance of a good example.
#100346 11/14/06 08:18 PM
Joined: Feb 2002
Posts: 375
G
Member
It appears that such work is cod ecompliant.

The NEC should reconsider the use of NM cable in blown foam insulation in walls but until they do ...

#100347 11/14/06 10:08 PM
Joined: Jan 2005
Posts: 5,445
Likes: 2
Cat Servant
Member
I must confess to having used foam ONCE to secure an existing box. In that case, water leaking from the shower on the opposite side of the brick wall had resulted in the masonry being too 'crumbly' to accept any anchors, and I was not comfortable with the box moving every time a plug was inserted into the receptacle.

(Not to worry- the leak had been solved, but the owner was not about to replace the entire wall!)

I am not all that concerned about any reaction between the foam and the cable jacket. Those foams are like an epoxy; rather than a solvent, they contain two materials that react with each other. Oddly enough, the "second" component is sometimes moisture in the air!

That aside, the liberal use of foam is, in my experience, a sure sign of a third-rate contractor. Foam is not cheap, either. I might not be able to cite for the use of foam ... but I sure can take that as a hint to look closer!

#100348 11/15/06 12:39 AM
Joined: Jul 2002
Posts: 717
M
Member
Over the years I have run into so many non-metallic boxes secured in block or brick wall with some type of grout added and the box pushed into it to secure the box. I wonder what amount of that substance, contaminates the romex sheath. I did it myself for a long time. Now I use spray can expanding foam to hold the box in the wall. It has worked out excellent, none have worked loose. My feeling is that it is alot better on the cable than a caustic cement. Even better is to run pvc down the void of the block if it is possible, but a lot of remodel does not allow for that.

Page 1 of 2 1 2

Link Copied to Clipboard
Powered by UBB.threads™ PHP Forum Software 7.7.5