Re: Nuisance tripping of 80 amp CB?
Mustang am I correct that you have a 3 phase 40 HP motor running 460 volts?
Table 430.150 shows that size motor as a 52 amp load.
The 80 amp breaker may be (probably is) too small for this motor.
430.52 allows a breaker 250% of the load current and you can move up to the next standard size.
52 x 2.5 = 130 amps.
The next standard size is a 150 amp.
You could safely, code compliantly move up to a 125 amp or a 150 amp breaker leaving the 6 AWG in place and still not worry about 'smoke'.
The feeder breaker has nothing to do with overload protection of the conductors.
By the way, the 8 AWGs you said where originally installed where not code compliant for a 52 amp motor.
[ June 15, 2005, 04:12 PM: Message edited by: iwire ]