15 amp circuit trips when heater plugged into it. Nothing else on circuit. Ammeter reads 12.5 amps at breaker. Same heater runs fine on an other circuit drawing same 12.5 amps
OK, bad breaker you say. Swapped breaker with one beside it in panel. Still trips. Breaker is not hot. Takes about 5 minutes to trip. Remove breaker and inspected bus. Looks perfect as does breaker contact.
What to check next?
Breaker panel is only about 15 years old FPE. I installed it and I also installed the circuit so I know where the cable runs exactly.
Don't bitch about FPE panel. We still install them new here in Canada. Very popular brand.
By change the breaker that is tripping a gfci breaker? Another thing you can do is instead of clamping the load wire, clamp the main line. Does your meter have a max hold feature that changes only when the voltage increases?