Originally Posted by BobSmitt
The wiring is already handling 30A, or at least that's how it's been set up since the 1960's without any apparent incident.
Being running that way for years without incident doesn't mean it was ever right.
If it was 12 AWG wires on a 30 amp breaker, it might run 100 years that way without apparent incident. It also might eventually (after many years) cook the insulation and make it more brittle than it would be otherwise.
It's about having a safety margin built in.