NM Insulation Temperature Rating

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stevee

Member
Ok, I understand that NM cable has 90'C conductors inside an outer jacket. And I understand that the 90'C rating is used for derating purposes and that the final ampacity of the conductors cannot be higher than the ampacity based on the 60'C rating.

Here's my question.

Can the conductors be connected to a 75'C Circuit Breaker?

Example: #12 NM Cable, no correction factor or adjustment factor needed based on installation. Ampacity in 60'C Column is 20A. Can this cable be connected to a 75'C 20A Circuit Breakers or must I use a 60/75'C Circuit Breaker?

I realize that most of my residential CB's will be 60/75'C I just want to know if it's acceptable or not..

Thanks,
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
Over current devices, outlets, terminal blocks, etc that have a rating of at least 60? can be connected to the NM as long as the 60? amapcity rating of the cable is not exceeded.
 

JDBrown

Senior Member
Location
California
Occupation
Electrical Engineer
This now begs the question, what's the purpose of 60/75 deg terminals, if they're no different from 75 deg terminals?
 
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