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Posted By: jes Mounting Stuff - 11/14/06 12:50 AM
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?
Posted By: Zapped Re: Mounting Stuff - 11/14/06 01:41 AM
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.
Posted By: macmikeman Re: Mounting Stuff - 11/14/06 02:48 AM
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?
Posted By: BigB Re: Mounting Stuff - 11/14/06 03:38 AM
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.
Posted By: iwire Re: Mounting Stuff - 11/14/06 10:20 AM
I don't see anything in the NEC that would prohibit this.
Posted By: Zapped Re: Mounting Stuff - 11/14/06 02:33 PM
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?
Posted By: Tom Re: Mounting Stuff - 11/14/06 11:01 PM
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).
Posted By: George Re: Mounting Stuff - 11/15/06 12:18 AM
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 ...
Posted By: renosteinke Re: Mounting Stuff - 11/15/06 02:08 AM
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!
Posted By: macmikeman Re: Mounting Stuff - 11/15/06 04:39 AM
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.
Posted By: walrus Re: Mounting Stuff - 11/15/06 10:10 AM
Canned foam is an excellant glue. It sticks to just about everything. Seems like a shady way to do a job though
Posted By: SteveFehr Re: Mounting Stuff - 11/15/06 04:13 PM
The foam doesn't even really need to adhere like superglue- if it holds the romex firmly in place as it expands around it and doesn't deteriorate or damage the cables, I see no reason why it wouldn't be acceptable.

It does surprise me that it isn't listed for the purpose. Wouldn't it require an engineers stamp to be used, if the foam wasn't listed?

Edit: actually, now that I think about it, that would be an interesting business model for a consulting PE as a side job- to specialize in going back into f'ed up installations that failed inspection to bless or reject or overwise non-code compliant installations. Think there would be much demand for that?

[This message has been edited by SteveFehr (edited 11-15-2006).]
Posted By: gfretwell Re: Mounting Stuff - 11/15/06 05:02 PM
Steve, that job already exists here. My wife came into a house (built by a guy who is gone) where they discovered at the final that the FEPAC was never called in (all the pre-drywall roughs). They called an engineering company that did some X-Ray vision inspection and signed off the FEPAC. I was surprised she got away with it
Posted By: EV607797 Re: Mounting Stuff - 11/15/06 06:34 PM
If that foam degrades the jacket on NM cable, there's going to be a huge problem around here. Nearly all new homes built around here have spray foam used everywhere. Some builders are even using it to plug holes where cable penetrates the top or bottom plates of stud walls, even interior ones.
Posted By: VAElec Re: Mounting Stuff - 11/16/06 10:20 PM
I have never used foam for mounting a box (have used plenty of mortar or epoxy for metal boxes in block) but I like the idea. A lot easier to apply than the methods I have used. Where I do use foam a lot is to seal penetrations into Sensitive Compartmented Information Facility (SCIF) areas. It is usually required by the clients we do service calls and build-outs for who are governments contractors and have to comply with Gov. Spec. to keep their contracts. In my experience, 90 percent of the time the only distribution gear in a SCIF is for IT so and circuits needed for additional equipment has to be pulled from outside the area. Keeps the feds happy I guess, and never have had any inspector bat an eye.
Posted By: SteveFehr Re: Mounting Stuff - 11/16/06 10:59 PM
We've got mil-spec monkey-goop for that, VAElec! Hey, I don't suppose you know anything about NSA SCIF grounding requirements, and how NSA requires shielding to be grounded?
Posted By: VAElec Re: Mounting Stuff - 11/16/06 11:46 PM
Steve,
I am not familiar with specific NSA requirements. ( I guess if I knew a lot about specifics I could say anything about it anyways, right?) With that said a quick google search “NSA SCIF grounding requirements” has some interesting finds. I know that the main thing that I have found when working with many agencies (either direct or as a sub) is that you have to be on the ball as they will reject work that far exceeds code requirements very quickly when it does not meet their spec as I am sure you know.

Now to the results. About the most informative result I found after a quick search is originally from the USAF. www.thememoryhole.org/mil/aia/aiacl33-1.pdf

A check list sheds light on a bit of the requirements, but not a whole lot of info. No surprise there eh'? As a side note, I was working about ¾ of a mile from the main NSA complex today. That place is closed up tight! I spent the first 18+ years of my life on and around USAF bases and facilities. Have lived on a SAC base that still doesn't show up on maps (I can say that it was north of a good part of habitated Canada and was not Alaska or Greenland), an Intel base in MA, and various other places and NSA is hardcore about keeping things buttoned up.

Oh, and I realize I didn't answer anything, sorry. Ha.
Posted By: SteveFehr Re: Mounting Stuff - 11/16/06 11:56 PM
I'll just give Ft. Meade a call on monday and get it straight from them, I guess. I've dealt plenty with SCIFs, but never with NSA SCIFs, so I wasn't sure what sort of things they require. Thanks for giving it a shot [Linked Image]

Oh, if anyone is lost, SCIF = Secure Compartmentalized Information Facility. It's a vault rated for information classified above top secret. Real PITA stuff to work with at any level of involvement!

[This message has been edited by SteveFehr (edited 11-16-2006).]
Posted By: VAElec Re: Mounting Stuff - 11/17/06 12:21 AM
PITA, 'nuff said.
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