Please be aware of possible danger!

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Old 02-16-19, 04:43 AM
J
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Exclamation Please be aware of possible danger!

Here is a helpful warning for all of you. The electrical problem I was having was in the wall. The wires shorted to the point the neutral wire was burned clean away.
This is the second time this happened to me once before with thermostat wire. Both times the wires were had that spray can foam insulation touching the wires.

That foam seems to have some kind of chemical reaction with wiring that eats at the wire to the point they become bare and short themselves out. I spayed that insulation where the problem outlet was years ago because the mice were chewing through the wall where the outlet was.

In the case of the thermostat wire that foam insulation was there when I bought the house and the thermostat wire was encased right through the middle of the insulation. That wire was eaten completely away when I pulled it from the foam to run a new line.

This is scary to me when I think of how many people us that spray foam around their receptacles. Please be aware of this!
 
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Old 02-16-19, 05:10 AM
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Is your breaker working as it should?
Wire should not burn off from a short if the breaker is working.

Maybe you had loose connection and caused wire to overheat ?

What kind of wire was there? Modern PVC insulated wire and very chemical resistant and is not reactive to spray foam as far as I know.
 
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Old 02-16-19, 05:21 AM
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I'm sorry but I do not believe this. More likely the mice ate the wires.

Can you post some pictures.
 
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Old 02-16-19, 05:33 AM
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I too would be concerned that you have a problem that is totally unrelated to spray foam insulation.
I have never heard of any problems like you describe and spent some time looking to see if any others experienced the same as you......... without success.

If you look for any type of controversy regarding spray foam around electrical wiring it has to do with potential heat build up around encased wiring but this appears to be unfounded.
This idea appears to only be a theory as no evidence of overheating caused by foam insulation has been documented.

Spray foam insulation has been around for many years, is subject to testing and approvals and there are no warnings or cautions that would be related to what you experienced.

I would suggest that you take a serious look and other wiring in your home as you may have more problems.
As far as I am concerned there are no known issue as you describe and think people should not be concerned about it.

Can you post clear photos of what you describe so that maybe someone can help you.
 
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Old 02-16-19, 12:04 PM
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I'm sorry but I do not believe this. More likely the mice ate the wires.
Agree! Mice (and squirrels) love chewing on NM cable sheathing and wire plastic insulation.
 
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Old 02-17-19, 06:46 PM
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Ass you can see there are no chew marks on the wire. Like I said this happened to me also with thermostat wire. It was dissolved right inside a large mass of foam insulation.
 
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Old 02-17-19, 07:24 PM
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If you look at the cable..... 1" from your fingers..... that looks chewed.

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Last edited by PJmax; 02-17-19 at 07:48 PM.
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Old 02-17-19, 08:20 PM
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I wish I still had the wire to send you. That part you see was melted. There was not one tooth mark on that wire.
 
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Old 02-17-19, 09:16 PM
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I do not see any foam on that cable. It looks like a nice new cable with chewed insulation.

It also looks like an extension cord not NMB cable.
 
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Old 02-18-19, 06:27 AM
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Polyurethane foam doesn't really dissolve much of anything. The propellants (isobutane, propane) can cause some short-term chemical reactions with certain types of foam, but will only last until the foam dries, and in construction terms, is irrelevant. Once dried, the foam is chemically inert and doesn't pose any issue for people or materials.

In addition, modern wiring is made of PVC and different types of thermoplastics that are pretty much impervious to everything. Even older wiring materials like fabric insulation really shouldn't interact with any building materials (though fabric insulation tends to degrade over time)

I find it VERY hard to believe that was done by the foam. It's not that I don't believe you, but maybe it's caused by other effects. Maybe there was a defect in the wire (mouse) and caused some heating which prompted the melting?
 
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Old 02-18-19, 10:53 AM
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Joed That would be the first extension cord I have ever seen with solid wire
 
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Old 02-18-19, 11:17 AM
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I would be curious to know if this was some sort of oddball cable -- perhaps even some type not rated for in wall use. Or a very old cable with natural rubber insulation, although it looks thermoplastic to me. Perhaps in that case the foam could have caused a problem. Is it possible the cable in question contacted some other sort of damage inside the wall cavity like a stray drywall nail? Or more extensive rodent damage than was first evident?

Even if the foam did damage the insulation, the foam itself is a strong electrical insulator so I don't know how electrical damage could develop given that the conductors would still be electrically isolated unless there was also some mechanical damage. For example, motor & transformer windings are dipped in urethane resins (same material as the spray foam) specifically for the purpose of insulating and protecting the wires.

But like the other guys, I have worked on many buildings that are fully sprayed with commercial two-part urethane foam insulations and have seen no adverse effect on the cabling. Likewise I use tons of one-part urethane canned foam (great stuff, etc) and never seen any adverse effect on the cable with that type either, nor am I aware of any reports in the trade magazines.
 
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