I have a customer who has a sub-panel fed by a 6/3 piece of AC. It's overcurrent protection is a double-pole 60AMP Homeline Square 'D' circuit breaker. One phase is operating at 53AMPS, the other at 43. On Tuesday, the circuit breaker tripped. I went there today and the breaker was RED-HOT. My question is, without running new #4 feeders to the sub-panel, can I upgrade to a double-pole 70 according to 310.16 using the 90ยบ column?
