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