ce2two said:
#6 THHN relative to romex (nm) is good for 75 amps max. section 310-16 ,90c/194 f.............used this for the longest time ........correct me if i'm wrong?????????? #8 ,55amps, #10 ,30 amps.....
You gotta build your circuit according to the
weakest link.
Here's your links:
1] lug
2] wire
3] raceway
1] Your breaker
lug with a #6 is rated for 60?C.
110.14(C)(1)(a) is telling you that certain
lug sizes should be assumed to be 60?C unless marked otherwise. . 110.14(C)(1), "..... Unless the equipment is listed and marked otherwise, .....". . If marked otherwise, you can use it as marked. . 75?C is very very common marking for smaller lug sizes. . And all common SquareD, Siemens, CutlerHammer, + GE
breakers are listed for
75?C.
The lug on your
load equipment is also most likely rated for
75?C.
So your lug amps with the #6 attached is
65a.
2] With Romex your
wire is THHN rated at 90?C.
#6 THHN is 75a.
Apply all
correction factors such as ambient correction from the bottom of T310.16 and over 3 conductors from T310.15(B)(2)(a).
I think it's safe to say that this installation doesn't have any correction factors so the #6 wire is
75a.
3] The
raceway is Romex.
334.80 limits Romex to 60?C.
So your #6 Romex amps are
55a.
1] lug is 65a.
2] wire is 75a.
3] raceway is 55a.
You gotta build your circuit according to the
weakest link and that's
55a.
For choice of breaker, you can "one-up" [240.4(B)].
"One-up" for 55a gives you a
60a breaker [240.6(A)].
Is the connected load 55a or less ? . If your load is continuous it can not be greater than 44a [44 x 1.25 = 55, 210.19(A)(1)]. . If the connected load is larger, then the wire is too small to remain. . It has to be replaced with larger conductors.