Expandable Foam as Duct Seal

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Sparky555

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I've recently run into two jobs (200A residential service and feeder J-box for an outbuilding subpanel) where the installation appears professional with the exception of the use of yellow expandable spray foam used to seal the conduit. I assumed this is a violation and the client said he knew electricians using expandable foam on all their installations.

Is there a product I'm not aware of that's suitable as duct seal? I'm assuming this is Great Stuff or similar.
 
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arossi

Member
I've been instructed by and personally witnessed several poco guys use sprayfoam to seal main feeders. They say it gets around the wire good to make a good seal. Only done it a couple of times myself.
 
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Sparky555

Senior Member
If this is a case where there is no NEC requirement to seal, is it then OK to use latex caulk, silicone caulk, construction adhesive, mortar, hydraulic cement, or whatever?
 
TwinCitySparky

TwinCitySparky

Senior Member
Location
Minnesota
I know its not an NEC thing but I've seen plenty evidence of mice chewing thru expanding foam in other applications... I dont think they do that with duct seal.

JMHSO
 
don_resqcapt19

don_resqcapt19

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Location
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Occupation
retired electrician
Some inspectors will cite a 110.12(B) violation for this unless you have a foam that has been tested and found not to damage the conductor insulation.
 
iwire

iwire

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don_resqcapt19 said:
Some inspectors will cite a 110.12(B) violation for this unless you have a foam that has been tested and found not to damage the conductor insulation.
Click to expand...

I know, but to me this is fairly ridiculous considering that the insulation contractors will use expanding form around all NM cables in a home due to building code requirements.

Has duct seal actually been tested or is it OK 'cause we have always used it?
 
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charlietuna

Senior Member
Expandible foam does not have a U.L. rating like "duct seal". Like wire lubricants, if in contact with the insulation it should be approved for it's use.. Duct seal can be easily removed--expandible foam can be impossible...
 
don_resqcapt19

don_resqcapt19

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retired electrician
iwire said:
I know, but to me this is fairly ridiculous considering that the insulation contractors will use expanding form around all NM cables in a home due to building code requirements.
Click to expand...
Maybe another reason to adopt the Chicago code.:grin:
Has duct seal actually been tested or is it OK 'cause we have always used it?
Click to expand...
I don't know if it has been tested, but the manufacturer's spec sheets say it won't damage the conductor insulation. I doubt that the expanding foams will either, but they might. I know it didn't cause any problems with my house service entrance where I filled the nipple between the outside meter and the panel with an expanding foam product and that has been in place for about 25 years.
 
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cadpoint

cadpoint

Senior Member
Location
Durham, NC
Here's a link to the UL for Through-penetration Firestop Systems, this is a broader test application as I skimmed it, it not to say what material to use but cross references ANSI aspects of type of conduit and what is listed for that application. I've only ever use a RED fire caulk, with Rate stopping and silicone for Hole sealing... where fire is not a concern, and or Specifications stated a requirement.

Is what I'm posting about
http://database.ul.com/cgi-bin/XYV/template/LISEXT/1FRAME/xhez_search.html

A broader "seal off" page of other things in construction
http://database.ul.com/cgi-bin/XYV/template/LISEXT/1FRAME/fireressrch.html

and the home UL database page:
http://database.ul.com/cgi-bin/XYV/template/LISEXT/1FRAME/index.htm

You can Use the "Specific Searches" for quick results!

Enjoy
 
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nakulak

Senior Member
charlietuna said:
Expandible foam does not have a U.L. rating like "duct seal". Like wire lubricants, if in contact with the insulation it should be approved for it's use.. Duct seal can be easily removed--expandible foam can be impossible...
Click to expand...

hire the mice in the other post to remove it
 
GUNNING

GUNNING

Senior Member
Location
Gainesville, Florida
how many seals does it take to seal a duct?

how many seals does it take to seal a duct?

There is a red fire caulk foam. Phone co people have been foaming there underground bores with cyanic foam for a long time till they took it away from them. Foam products are now latex based. It might not do what a good duct seal product might do, depends on environment, I would think. :cool:
 
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