Gfi circuit breaker defective
I have a 15 amp 240 volt, ground fault circuit breaker (special order and pricey). I have this connected via 14/2 wire to a deep well pump submersed into the lake, and a 500 watt baseboard heater. This has been connected for 16 months with no problems. This weekend I could not get the circuit breaker to work without it tripping. I tried disconnecting the wires to the circuit breaker (no load) and it still tripped, I tried moving it to another location on the panel box still tripped. As a last resort I took out the gfi circuit breaker and connected a (on hand) 20 amp 240 volt circuit breaker. It did trip once but worked fine for the rest of the weekend (Saturday and Sunday). There has been record rainfall at the cottage the last couple of weeks and there have always been what appears to be voltage drops on the service as the lights will dim with no other loads (no motors or heavy voltage draws starting up when the lights dim.
Any ideas? I have checked the line at all locations looking for animal damage or obvious shorts (electrical boxes, box connectors, etc. no obvious shorts.