# Spray foam?



## Elephante (Nov 16, 2011)

Can you spray foam over romex wires? Are there any derating issues by doing that?


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## wildleg (Apr 12, 2009)

I guess there would be if it melts all the insulation away. otherwise, I think there would have to be extenuating circumstances (o/w known as bundling) for there to be an issue


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## LightsOn81 (Jan 6, 2012)

Inspector here told us that it had to be fire rated


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## 360max (Jun 10, 2011)

LightsOn81 said:


> Inspector here told us that it had to be fire rated


..are you going thru a fire rated wall?


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## Elephante (Nov 16, 2011)

wildleg said:


> I guess there would be if it melts all the insulation away. otherwise, I think there would have to be extenuating circumstances (o/w known as bundling) for there to be an issue


Have you ever seen bundling in a residential application?


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## captkirk (Nov 21, 2007)

is spray foam any different than being packed in a wall with insulation..


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## Elephante (Nov 16, 2011)

captkirk said:


> is spray foam any different than being packed in a wall with insulation..


foam attaches to the cable . thats the only difference i can think of


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## captkirk (Nov 21, 2007)

personally i dont think its a problem, only because ive done several jobs with spray foam insulation on new homes and its never been mentioned.. I wouldnt worry about to much..


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## Elephante (Nov 16, 2011)

captkirk said:


> personally i dont think its a problem, only because ive done several jobs with spray foam insulation on new homes and its never been mentioned.. I wouldnt worry about to much..


Not really worried..I'm just waiting for an inspector to say someting."That can't be like that. You have to channel the foam out."lol


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## socalelect (Nov 14, 2011)

is the foam you speak of like " great stuff " that stuff is anything but great


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## captkirk (Nov 21, 2007)

we had one guy give us a hard time once with MC and fire insulation in a new daycare center. We had to break it off in some areas.


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## CDN EC (Jul 31, 2011)

Had to do it on one local resi home theatre job. Passed inspection just fine, the foam doesn't eat away at the plastic.


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## McClary’s Electrical (Feb 21, 2009)

Where more than two NM cables containing two or
more current-carrying conductors are installed, without
maintaining spacing between the cables, through the same
opening in wood framing that is to be fire- or draft-stopped
using thermal insulation, caulk, or sealing foam, the allowable
ampacity of each conductor shall be adjusted in accordance
with Table 310.15(B)(2)(a) and the provisions of
310.15(A)(2), Exception, shall not apply.
Where more than two NM cables containing two or
more current-carrying conductors are installed in contact
with thermal insulation without maintaining spacing between
cables, the allowable ampacity of each conductor​shall be adjusted in accordance with Table 310.15(B)(2)(a).


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## chicken steve (Mar 22, 2011)

Elephante said:


> Can you spray foam over romex wires? Are there any derating issues by doing that?


 
334.80



_thank you McClary_


~CS~


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## chicken steve (Mar 22, 2011)

mcclary's electrical said:


> Where more than two NM cables containing two or​
> more current-carrying conductors are installed, without
> maintaining spacing between the cables, through the same
> opening in wood framing that is to be fire- or draft-stopped
> ...


 
you wouldn't happen to have the HB commentary following that?

~CS~


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## McClary’s Electrical (Feb 21, 2009)

chicken steve said:


> you wouldn't happen to have the HB commentary following that?
> 
> ~CS~


 
I have a handbook, but not that I can cut and paste to here.


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## Stab&Shoot (Aug 23, 2011)

Great Stuff spray foam is not permissible as a draft stop in any application thicker than 1". So if you drill through a 2"x4" bottom plate, then draft stop it with spray foam- you are in violation. I know this b/c an inspector failed me and I challenged him. I called the manufacturer of the foam to request a ms data sheet and was informed by Great stuff that it in fact is not good for any application over 1" thick. Had to dig all foam out holes and re caulk. Have never purchased as a draft stop again.


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## leland (Dec 28, 2007)

CDN mini-EC said:


> Had to do it on one local resi home theatre job. Passed inspection just fine, the foam doesn't eat away at the plastic.



A few years back I had that foam ins. burn thru some bell/phone cables.
What a PITA replacing that. Now I use the good cable.


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## jza (Oct 31, 2009)

How about when some jerk off fills a receptacle box with spray foam on an exterior wall, those are always fun.


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## wildleg (Apr 12, 2009)

I've only used the spray foam a few times on the odd resi job I did. I never had the issue with eating the sheath or with the inspector saying it wasn't suitable, as were indicated above. It seems ludicrous that the foam can't be used for draft stopping (AFAIK they allow anything and everything around here for draft stopping) - of course, I'm not talking about firestopping, which requires a rated material. And draftstopping in a wood wall that requires fire blocking, would of course require fire rated material. So I'm a little suprised that foam is not allowed - I'm gonna check that out next time I have a job like that. Anybody have an idea where that might be in any of the codes ? (IRC ?)


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## Stab&Shoot (Aug 23, 2011)

Exactly my thoughts wildleg. Which is why I challenged AHJ. You will not find a code that is against the foam. It only goes against manufactures specs of foam. And if you contact manufacturer of foam, you will also find that it has no use as a fire stop either. I was shocked. But it can be used to say- seal around a whole cut in 3/4" floor board- as that does not violate the 1" thickness rule. Yeah I know sounds like Bullsh*t right?! Was a big shocker to me. The whole situation ended with me apologising to AHJ for doubting their profound wisdom and cussing out the manufacturer of the spray foam. The job I'm referring to was a single family 1300 sqr ft house. Which only requires draft stop-not fire stop.


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## McClary’s Electrical (Feb 21, 2009)

Stab&Shoot said:


> Exactly my thoughts wildleg. Which is why I challenged AHJ. You will not find a code that is against the foam. It only goes against manufactures specs of foam. And if you contact manufacturer of foam, you will also find that it has no use as a fire stop either. I was shocked. But it can be used to say- seal around a whole cut in 3/4" floor board- as that does not violate the 1" thickness rule. Yeah I know sounds like Bullsh*t right?! Was a big shocker to me. The whole situation ended with me apologising to AHJ for doubting their profound wisdom and cussing out the manufacturer of the spray foam. The job I'm referring to was a single family 1300 sqr ft house. Which only requires draft stop-not fire stop.


I think the ahj is wrong. There is nothing that says the full 3.5 inched of a bottom plate be filled completely. Spray it in the hole to the specd thickness,.and that is all that is needed. I can normally take one can and do a whole house full of penetrations. You will not find any code, anywhere, that requires the entire depth of penetration to be filled


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## Sparky J (May 17, 2011)

jza said:


> How about when some jerk off fills a receptacle box with spray foam on an exterior wall, those are always fun.


Yep had some jackwagon do that to some kitchen counter outlets in a rental town home I had to work in last week . I'd love to get a can or two and shove them in his tailpipe.


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## green light (Oct 12, 2011)

When I was an apprentice we wired an Albertsons grocery store. We fed our MDP underground with 4" PVC's. The inspector made us foam in the bell ends where the wire left the pipe, but he said we had to use a foam product that wouldnt degrade the insulation. I dont know what "brand" we ended up using, but he ok'd it whatever it was:thumbup: I see that there are bio based foams, polyurethane, ?. Any one know if one type of foam is more likely to degrade insulation than another?


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## leland (Dec 28, 2007)

green light said:


> When I was an apprentice we wired an Albertsons grocery store. We fed our MDP underground with 4" PVC's. The inspector made us foam in the bell ends where the wire left the pipe, but he said we had to use a foam product that wouldnt degrade the insulation. I dont know what "brand" we ended up using, but he ok'd it whatever it was:thumbup: I see that there are bio based foams, polyurethane, ?. Any one know if one type of foam is more likely to degrade insulation than another?



Stay away from petroleum based.

This situation,duct seal would be the correct method.


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## NJWVUGrad (May 12, 2011)

jza said:


> How about when some jerk off fills a receptacle box with spray foam on an exterior wall, those are always fun.


Ha!...I thought I was the only person that had ever happened too. Only in my case it was not just exterior boxes, it was every box in the damn house.

God how I hate those damn DIY shows.


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## jza (Oct 31, 2009)

Spray foam... I put that **** on everything.


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## manchestersparky (Mar 25, 2007)

chicken steve said:


> you wouldn't happen to have the HB commentary following that?
> 
> ~CS~


 Here it is, I did not copy the calculation examples or the commentary for the examples

 Section 334.80 references, 310.15 for determining the ampacities of Types NM, NMC, and NMS cable. As stated in 310.15(B)(3)(a);”…where single conductors or multiconductor cables are installed without maintaining spacing for a continuous length longer than 600mm (24 in) and are not installed in raceways, the allowable ampacity of each conductor shall be reduced as shown in Table 310.15(B)(3)(a).” 
Failure to apply the appropriate ampacity adjustment factor called for by this table, where nonmetallic-sheathed cables are stacked or bundled without maintaining spacing, can lead to overheating of conductors. The ampacity adjustment requirements prevent overheating of type NM conductors where passing through wood-framed draft- and fire-stopping material. The ampacity adjustment requirement for installations of more than two cables that are in direct contact with thermal insulation is intended to prevent overheating of type NM conductors. Not only is thermal insulation provided within structures to reduce heat loss or heat gain, but the same thermal insulation material may be used to control sound within a structure as well.


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