Frodo- Didn't mean anything personal, just stating facts.
Plumbers size things according to the load. We do not- we size according to the fuse/ circuit breaker, as the cited NEC says. This is because of the possibility of a short circuit; we want the wire to not be damaged before the fuse blows. If, on the other hand, a water pipe breaks, the leak will in no way damage the remaining pipe!
Just because a lot of people do things wrong does not make them right. Just because you can 'get away' doing something does not change that error into wisdom.
A large role is played in the NEC by science, engineering, and loss data. While, for any "rule" there may be some circumstance that justifies "bending" it, these are "exceptions," usually specified by the code, and the rule is still a rule.
I believe that the use of #14, even with 15 amp protection, is foolish in today's home. The second paragraph (90-1b) of the code admits that simply complying with the NEC may not be adequate for good service or future expansion." The next paragraph (90-1c) notes that the code is neither a design specification or instruction manual. In other words, it is very possible to do something that is foolish, but still "legal."
Now, if a man cannot be bothered to learn, and insists that his "feeling" is somehow wiser than the sum of everyone else's experiences, then there is no hope for him.
Putting #14 wire anywhere on a 20 amp circuit is simply wrong. Do it, and you're a fool. Undersize your circuits for reasonably expected loads, and you're possibly a legal fool.
Now, it is possible that I'm mis-informed. Perhaps someone could explain to me the virtues of undersized wired, and over-fused circuits?
