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I am looking at a residential (all kinds of ugly electrical) job in Ft. Worth Texas. Where the ambient temp in the summer is very hot in the attic ( any links to ambient temp in different parts of the country? I know I've seen them before). Someone has moved the service to the other side of the house to avoid the service drop over the pool. They used a old 125 amp zinsco MLO panel with 125 amp circuit breaker with 3- 1/0 feeders and # 6 solid GRN. approximately 60 '. to the sub panel ( branch circuits from existing panel). My question is about the sub feeders run through the attic with schedule 40 electrical PVC. What is the NEC code on the max temp and thermal expansion or any other problems dealing with PVC in a residential attic. Most electrical contractors, as I , will use EMT or what are the most efficient types of romex style cables SEU, USE, M/C , cable tray. Does the excessive heat with conductors in PVC cause toxic fumes also? Toxic fumes in a residential fire? Thanks for your support.


Senior Member
Kent, WA
NEC 352.12(D) would most likely prohibit this (assuming the ambient temperature gets over 122F for sustained periods, and the conduit isn't listed for high ambient temps).

PVC when it burns can give off toxic fumes. But I don't see why that matters in an attic (attic should not be vented into the living space).

I'd think this would be a good application for SER cable or flex metal conduit. With the high ambient, may actually be a decent use for SER since you are limited to the 60C rating for ampacity, yet the thermal derating is going to force most any conductor there anyway.

EMT would be fine too, but dealing with 10' sticks of conduit in an attic may be a challenge. As long as it isn't very accessible up there so physical damage isn't a concern, cable or flex conduit seems easier.

The #6 solid in a raceway is a violation too.
Thanks for the Support

Thanks for the Support

Also there is no main or dead front cover at the main panel protecting the other breakers along with the 125amp. Its on the west side of the house . The ledgend has burnt off inside. There are countless other violations. THANKS FOR THE REPLY and your support .Its great to talk to other electricians who have expertise. THE SELLER OF THIS HOUSE SAYS EVERYTHING WAS DONE PRIOR TO HIS KNOWLEDGE. I 'am trying to get this written up before this afternoon when I have to meet with the buyer. We'll see if the list will be too much. Thanks again for being a sound board :cool:
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