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NatalieEGH
join:2013-05-18
East Saint Louis, IL

NatalieEGH

Member

Derating of electrical wiring due to house insulation

I am rewiring my home both to upgrade the service and to bring up to current code. After I rewire, I will be fully insulating the house with foam insulation in the exterior walls and around duct work, 18 inches of dense pack insulation in the attic area, and if possible 1" thick vacuum insulated foam behind electrical boxes on exterior walls (2x4 construction so may not have room behind the boxes).

This will result in the wiring not being able to efficiently cool by transfer heat from the wires. I will mostly be using 12-2 and 12-3 (20 amp circuits) romex with one circuit using 10-2 (30 amp circuit).

Should I de-rate the wiring? If so, how much? Should I use 10-2 and 10-3 even though they will be on 20 amp circuits, and the 8-2 for the one 30 amp circuit?

John Galt6
Forward, March
Premium Member
join:2004-09-30
Happy Camp

John Galt6

Premium Member

Are you going to use NM-B?
NatalieEGH
join:2013-05-18
East Saint Louis, IL

NatalieEGH

Member

Yes, I am planning to use NM-B. I believe its rating is to 194 degrees Farenheit (90 degrees Celcius).

John Galt6
Forward, March
Premium Member
join:2004-09-30
Happy Camp

John Galt6

Premium Member

This document might answer your question:

»www.nema.org/Technical/D ··· tion.pdf
NatalieEGH
join:2013-05-18
East Saint Louis, IL

1 recommendation

NatalieEGH

Member

Thank you very much.

I expect to have no wall wires running in bundles. I will have to be more careful above the ceiling, but that should more be remembering not to let the wires be too close than any other problem.
54067323 (banned)
join:2012-09-25
Tuscaloosa, AL

1 edit

54067323 (banned) to NatalieEGH

Member

to NatalieEGH
?

John Galt6
Forward, March
Premium Member
join:2004-09-30
Happy Camp

John Galt6 to NatalieEGH

Premium Member

to NatalieEGH
said by NatalieEGH:

Thank you very much.

Certainly...glad I could help.

Oh, by the way, welcome to DSLReports and the Home Improvement forum.