NM-B termination temperature limitations

[electrician09]

I understand according to article 334.112 NM-B conductor insulation shall be rated 90c , but the ampacity must be sized according to the 60c Column. And only use 90 for correction purposes.

However is NM-B allowed to be terminated to a straight 75c breaker or must it only be terminated to a 60/75c breaker?

Example: two pole 30 amp breaker with a 75c only wire rating, allowed to have 10 awg NM-B terminated to it since the conductor insulation is rated for 90c but the cable assembly ampacity must be rated from the 60c column.

 

[augie47]

The 60 deg NM is the limiting factor. It can be terminated on any device/connector rated at 60 or above.

 

[electrician09]

Thank you for the response Augie, as I read and understand it NM-B shall be permitted to be terminated to a 75c wire only breaker correct?

 

[electrician09]

The 60 deg NM is the limiting factor. It can be terminated on any device/connector rated at 60 or above.

Thank you for the response Augie, as I read and understand it NM-B shall be permitted to be terminated to a 75c wire only breaker correct?

 

[augie47]

That is correct. The ampacity of the NM cable would still be 60 deg so the breaker ampacity would should not exceed the 60 deg rating unless it qualifies under one of the 240.4(G) categories.
For example, a #10 could terminate on any device/connector rated 60 deg or higher but the ampacity would still be 30 amps.