Ampacity of NMC

[brichter]

Currently having disagreements about the ampacity of NM cable. I say maximum of 40 amps on #8 and 55 amps on #6. Others say 50 amps is acceptable for #8 and 60 amps for #6. Comments Please.

 

[iwire]

334.80 Ampacity.
The ampacity of Types NM, NMC, and NMS cable shall be determined in accordance with 310.15. The ampacity shall be in accordance with the 60?C (140?F) conductor temperature rating. The 90?C (194?F) rating shall be permitted to be used for ampacity derating purposes, provided the final derated ampacity does not exceed that for a 60?C (140?F) rated conductor. The ampacity of Types NM, NMC, and NMS cable installed in cable tray shall be determined in accordance with 392.11.

 

[scwirenut]

however, if your #8 is for a range, and your #6 is for a HVAC, 50amp and 60amp breakers ok

 

[paul32]

however, if your #8 is for a range, and your #6 is for a HVAC, 50amp and 60amp breakers ok

Based on what?

8 AWG NM for a range is 40A. The HVAC depends on the nameplate.

 

[scwirenut]

i stand corrected, forgot that with nm you have to use 60 degree table even though you have 75 degree terminals.