Nordic Spa keeps tripping GFI

I just installed a Spa and it keeps tripping the 50A GFI. I had a competent, licensed master electrician do the wiring, and I've used him before. He's very much by the book, constantly quoting the NEC, so I feel sure the wiring is all correct and by the book.
Just not sure why (on a daily basis) I'll walk out to it, lift the lid, and see the panel dark. I'll go and reset the breaker, and it's fine. Never happens while I'm around, so I don't quite know what's going on?
Any responses will be greatly appreciated.
John
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John Gordon
jrgordon (at) knology (dot) net
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It sounds like moisture is getting to something where it should not. Since it seems to be happening overnight, I would guess the cool temperatures are causing condensation somewhere that is causing a ground fault.
Sorry I can't pin it down any closer, but it could be almost anywhere. Is there any way of disconnecting parts of the system at a time (like turn off the heater for one day, the pump the next etc.) it might help you pin it down. BTW just turning it off dose not guarantee that it will not GF.
Your electrician should be able to help, but it may take him a few tries to find it himself. I doubt if it was his fault, although I can think of a couple of ways it may have been.
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Joseph E. Meehan

26 + 6 = 1 It's Irish Math
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