Just want to be sure I have Amperacity right...

[Toller]

NMC is rated for its 140 degree amperacity, regardless that it is actually

190 degrees insulation; so #8 copper used to feed a subpanel needs a 40a breaker. #6 can have a 60a breaker because it is 55a and rounded up to the nearest size.

I want 50a capacity, so I need #6.

Is this correct? Just want to be sure.

[Doug Miller]

For the benefit of those who may not know... wire and cable are temperature-rated in degrees CELSIUS. NM is rated at 60 degrees C. Toller is referring to the Fahrenheit equivalent.

BTW, it's "ampacity".

You sure about that? (90 C = 194 F, BTW)

Correct.

Correct.

Yes, it is. Make sure you use a 4-wire cable, and keep the neutral and ground

*separated* in the subpanel.

[zxcvbob]

Yes, but from memory, you also could use #6 aluminum SE (SER) cable, or #8 THHN wire in conduit (also depends on the temperature rating of the terminals)

Best regards, Bob