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Is spray foam inside electrical outlet like this a fire hazard or not?

Is spray foam inside electrical outlet like this a fire hazard or not?

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  #1  
Old 10-29-18, 10:29 AM
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Is spray foam inside electrical outlet like this a fire hazard or not?

Hello,

The goal is to air seal outlets and light switches on exterior walls. A lot of cold air comes through the knockout holes and through the outlet itself.

I did a few outlets with Great Stuff, the blue can that doesn't expand so drastically, and this is the result.

I managed to place the tip of the straw even inside the knockout holes for the wires and sprayed there and allowed a little to expand inside in order to seal the hole.

The foam is not touching anything but the white sleeve that wraps the wires.
Also, there were unused knockout tabs on the bottom that had holes to make it easier to punch out, so I sprayed a little there to cover them too.
I was able to compress the foam with my fingers as it was curing and was pliable.

What do you think?
I got a little paranoid after the fact and hope the way I did it, only filling the back of the outlet where the wires come in and around the sleeves, is not a fire hazard.

All outlets have new outlets installed.
Thanks
 
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  #2  
Old 10-29-18, 11:11 AM
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I'm not a huge fan of how much foam there is inside the box. I would probably take a knife and trim it from around the outside, and try to get most of it out of the box.

The issue is that expanding foam is pretty flammable, and one of the main purposes of the electrical box is to contain any unexpected heat or sparks in the box. By adding foam in the box, you're adding burnable material. It's of course highly unlikely to be an issue... but I wouldn't want to risk it.

No issue with the foam against the cables outside the box.
 
  #3  
Old 10-29-18, 11:22 AM
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Thank you for replying.

Before I go through the monumental job of removing the foam from these outlets and switches.

I'd like to understand how the specific way I applied this is a fire hazard.

I understand that maybe someone who completely fills up the inside of the box with this foam and then sticks the outlet back in may be asking for trouble, but if you just put foam around the outer sleeves of the wires "in the back" like this, how is that dangerous?

I see many applying the foam around electrical wires around the white sleeve as I did here, however I understand this box is enclosed, etc. Just trying to make sense of this and learn.

Also, the foam around the edges of the box between the drywall and the box, is actually closer to the outlets' bare wire connectors, so how can that be "recommended" by the manufacturer to seal gaps if the product is this flammable?

Thanks

By the way, I can't reach from around the outside of the box or how do you mean? I could try to remove what I can from the knockout holes, but want to be sure this is really necessary as this is a pain to remove and if I do it I will be leaving those holes exposed again to air. Of course, I will have to do it if this really is a fire hazard and I am in danger. Thanks for the insight.
 
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Old 10-29-18, 11:22 AM
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The boxes are UL approved, the foam is not.

It's a sure fire way to piss off an electrician. They make fire rated foam that should be used for fireblocking / near combustibles. Even then, electricians wont like it.
 
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Old 10-29-18, 01:23 PM
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Ok, I removed as much as I could from the knockouts inside at the back and trimmed the outside edges where it meets the drywall.

I guess the very little foam material now inside the box will not be a realistic issue even if there is s spark or other problem right?

I was thinking that since I removed most of it from the knockouts at the back, maybe I should seal and cover the little foam that remains there with a little silicone to seal it well and also, since silicone is not flammable according to DAP customer service, then it will also serve as a coating for the minimal foam inside? THoughts?
The goal was to prevent air from coming in on this poorly insulated home.

thanks for you patience and input.
 
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Old 10-29-18, 02:15 PM
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I think as long as the foam is not inside the electrical box, it's within the listed use of the product. It's used all the time in various types of construction, and while perhaps a theoretical risk is clearly not a major problem.
 
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Old 10-29-18, 03:19 PM
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Why didn't you use those outlet and light switch insulation pads? That's what their made for. I try to avoid using spray foam for exactly the reasons you ran into.
 
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Old 10-29-18, 07:56 PM
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Those foam covers only cover the outer edges of the box. You have knockout holes in the back that let air inside and through the outlet connections where you put the prongs.

I removed most of it and covered the knockout holes and whatever remnants of foam around that area with Dap silicone. It is not flammable and is water based so that should do it.

I will do the remaining outlets and switches only with silicone caulk.

what a pain!
 
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Old 10-29-18, 08:04 PM
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Dap silicone. It is not flammable and is water based
I hope you are talking about Dap Alex Plus (acrylic latex caulk plus silicone, which is a paintable latex product) and not "Dap silicone". (Which is a completely different product and is 100% silicone).
only with silicone caulk.
for the benefit of other readers, you do not use 100% silicone on surfaces you intend on painting.
 
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Old 10-29-18, 08:11 PM
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It is Dap 230 which is like silicone and cleans with water. Not water based, sorry I mixed that up.
This one dries clear and is super flexible and tough like silicone. DAP stated I could use latex or silicone or this one if I was looking for non flammable.

I guess any caulk would work for sealing the back of an electrical box.

Picture of another outlet with foam trimmed and removed the most I could from inside and then caulked with DAP 230. It will dry clear.
 
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Old 10-29-18, 08:20 PM
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I don't know why you would call Dap Dynaflex 230 "Dap silicone", but that clears that up. Thank you.

And yes, most latex products are water based, cleanup with water and should not be stored below 32F.
 
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Old 10-29-18, 08:24 PM
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With so many caulks I have bought it is easy to mix them up. Especially since the back of DAP 230 states silicone like toughness or something like that. Sorry for the mix up. Hope I am in the clear with the use of this product for sealing around the wires in the box.
 
  #13  
Old 10-30-18, 09:08 PM
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What you had on post #5 would been perfectly fine. I don't know why you went extra step to clean foams and caulk it.

I see wire nut or crimp is missing on ground wires in your caulked junction box. There bundle of ground wires should have a wire nut on it.


By the way, Dynaflex is a great caulk. Stays flexible and almost no shrinkage.
When it dries, it is soft and stretches like a rubber.

I use it in place of painter's caulk when there is a large gap or some movement is expected.
 
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Old 10-31-18, 10:55 AM
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I agree, I think the pic you have in #5 is perfect No excess foam inside the box and well air sealed.

Caulk addition is fine, but I don't think was necessary. Again, if you picture a spark or overheating in the box, there's nothing left to start burning - which is a good thing!
 
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Old 11-01-18, 09:40 AM
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Originally Posted by Zorfdt View Post
I agree, I think the pic you have in #5 is perfect No excess foam inside the box and well air sealed.

Caulk addition is fine, but I don't think was necessary. Again, if you picture a spark or overheating in the box, there's nothing left to start burning - which is a good thing!

I would have left it as shown on #5 if I was sure that the gaps were completely filled with foam, but the thing is that when you push the wires back into the box so you can screw the outlet to the box, all those wires push the foam back and gaps open up a bit. Since I did so much work, I just didn't want to find out later that there is still air coming through so I went ahead and caulked it while I had them open. It is a pain to do this and wanted to be sure.

Also, I bought some fire caulk by 3m (intumecent) to do the other outlets I plan on doing. This time no foam will be used Only red fiery expensive caulk!
 
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Old 11-01-18, 10:28 AM
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I know you're going above code for energy-efficiency reasons, but for the benefit of other readers; the expensive fire blocking caulk or foam is only required to seal penetrations through rated fire walls. Examples in typical residential construction include holes bored from one floor to another; the wall and/or ceiling that separates an attached garage from a living space; the underside of stairwells; or in some jurisdictions the walls and ceiling around a gas-burning appliance like a furnace or boiler.
 
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Old 12-31-18, 07:01 AM
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I'm starting to do this same job. Why couldn't you use a fireblock expandable foam? Then you wouldn't need to do a major cleanup.
 
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Old 12-31-18, 08:50 AM
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You can, it's just much more expensive than other sealing products. As a contractor we'd only use it where required by code.
 
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