ECN Forum Forums Code Related Discussion NEC & other Code issues derating

I'm not 100 per cent convinced Don, I read the words in 210.19(A)(1) and they say "the branch circuit conductors shall have an ampacity not less than the load to be served." It goes on to say the rule applies before the application of any adjustment or correction factors"and this rule applies to everything in Chapter 1-4
How about this example:
8000va water heater
1.25 x 8000 = 10000va
10000va ÷ 240 = 41.5 (42a)
Assume 75° terminations and THHN wire
45a overcurrent protection
# 8 awg conductor
Raceway has 6 conductors in ambient of 86°F
Adjusted ampacity 55 x .8 = 44a
44a conductor will carry the load of 33.3 a. and we are allowed to round up to 45a overcurrent device.
Rating of circuit is still 45a. per 210.3

Okay Don, I've got my kevlar vest on and my PPE gear, so let the sparks fly

George,
The rounding of of the overcurrent protection does not change the ampacity of the conductor. Any place that the code calls for a conductor of a minimum ampacity, that must be the ampacity of the conductor under the conditons where that conductor is installed. Remember that 310.15(B) tells us that a conductors ampacity shall be as specified in the ampacity tables as modified by (1) through (6). The temperature correction factors are part of the ampacity tables and the adjustment factor for more than 3 conductors in a raceway or cable is 310.15(B)(2).
This is an ongoing problem with the use of the code. In the 2005 code they changed the wording to say that you cannot use the provisions of 240.4(B) for tap conductors. This was not a rule change, but so many code users were missing the fact that 240.4(B) does not change the conductor ampacity. The tap rules are like the rule that I cited in 440.32. They require a minimum conductor ampacity. Some additional sections that require a minimum conductor ampacity are 424.3(B), 424.82, 426.4, 427.4, 430.22, 645.5, 669.5, 680.9. In all of these cases the rule requires a branch circuit conductor ampacity of 125% of the nameplate current. In all of these cases that conductor would have to have that minimum ampacity after the application of the adjustment and/or correction factors.
If the code section that covers a installation does not require a minimum conductor ampacity, then you are correct and the provisions of 210.19(A)(1) apply. The don't apply where other code sections set a minimum conductor ampacity.
Don