My GFI is tripping overnight for some unknown reason. After work, I can manually turn on the tub for however long I want with whatever features I want, and it will be just fine. I then go to bed, come back in the morning, and the GFI is *always* tripped.

The only thing that happens during the night is that an auto filter cycle runs from 2am - 4am. The filter cycle includes one pump at low speed, and maybe the heater, if necessary.

Is it possible that the spa pack and the auto filter cycle is somehow tripping the GFI? Are there some specific "auto cycle" relays or something that may have gone bad?

Tub is late 90's Jacuzzi, platinum series - Balboa F106 spa pack. Heater is brand new Balboa. Blower is disconnected and removed. GFI is 50A made by GE.

Just for kicks and experiments, remove both of the buss bars going to the heater element and see if it stays running overnight. I am suspecting a defective heater.

I have the same problem with a 2000 Sundance Optima Spa; every night the circuit breaker was tripping. I changed the filter cycle start time, and the GFCI tripped as soon as the filter cycle started. This was very repeatable as I kept changing the time and starting the filter cycle again and again. I tried removing the connections for different components and found that the problem went away when the ozonator was not connected, but it did not go away when I disconnected pump1 or the heater (pump2 is permanently disconnected). I put in a new ozonator, but the GFCI still trips whenever ithe ozonator is connected and the filter cycle starts. Any advice?