Spray foam over wiring

[6768rogues]

My son has a large barn and he plans to wire it. One thought was to attach Romex to the sidewall girts then insulate and finish the inside of the walls. He might have the sidewalls insulated with spray foam. That would leave the Romex embedded in the spray foam. Will that cause the wiring to overheat?

 

[jbberns]

That is the same as any other insulation in walls. Be fine. Just hard to add anything later.

 

[6768rogues]

My concern is due to other insulations that are fibrous allowing for some cooling for the wires. Because wires in a bundle are a concern, I thought that perhaps there would also be a concern about having a substantial length of wire encased in a tight cocoon of foam insulation. Thanks for your response.

 

[allinon72]

I'm no electrical expert but romex doesn't get hot?

 

[green.bubbly]

I'm no electrical expert but romex doesn't get hot?

From what I understand, you are semi-correct. A properly sized Romex out in the open should not get "hot".

However, there is a concern if several runs are bundled together and surrounded by something like a conduit.

That said, I have not read anything concerning spray foam around Romex.

 

[jbberns]

I wouldn't tie wrap ten together and then spray foam it. But a few of them will be fine.

 

[kbs2244]

Go for it.
It has been done more times than be counted.
If bad things have happened because of it the regulations would be in place to stop it.

In general, construction codes are very conservative and very reactive.
If you are lucky there is some property rights concern thrown in.

If it is not specifically prohibited, the best guess id that it hasn’t caused any problem in the past.

 

[cowboyjosh]

It'll be fine.

In the highly unlikely event a fire starts from overheated wiring covered in spray foam, insurance will build you a spiffy new barn, and you'll know better next time.

 

[pattenp]

Actually it will get hot. That's why there's a code section for proper installation and the requirement to size NM cable from the 60C degree column of the wiring sizing tables.

I'm no electrical expert but romex doesn't get hot?

 

[Td_20]

You will be fine as long as you don't over load the circuit.
May be installed in locations with temperatures up to 90°C but with the ampacity limited to that of 60°C conductors

In general, wire should carry current continuously at no more than 80% of its rating.
i.e. 20 amp wire should be loaded to no more then 16 amp continuously.
If your running muitple circuits in a pathway or conduit you you can only run so many of certain size together i.e. 6 of #8awg in 3/4 inch emt conduit.