I have just installed a new outdoor sauna. The new sauna heater trips the GFI breaker when the thermostat shuts the heater off after reaching the specified temperature.

I have a 50 amp GFI breaker in the house 200amp load box. From there I ran #6 wire for 120 feet to an external weather proof sub load box. In the sub load box I have two standard breakers, a 20 amp breaker which feeds the light circuits in and outside the sauna via #12 wire, and a 30 amp breaker which feeds the sauna header via #10 wire. These breakers are not tripping.

The heater is 1 phase 240, 6,000 kw. It’s drawing 25 amps on one leg and 26 amps on the second leg of the 240 circuit.

The manufacturer suggested burning the heater in on a standard breaker to burn of any condensation that may have entered the element tubes. I ran the heater continuously for four hours and that did not cure the problem.

Any suggestions would be appreciated.

Thank you

Bill

I suspect the long wire distance, due to high capacitance of the long feeder, along with the normal arcing that occurs at the contactor is causing the nuisance tripping.

I would suggest relocating the GFI breaker closer to the tub, using a standard breaker at the panel.

Thank you for you quick response and advice.

The main panel and the sub panel are different manufacturers and to move the GFI to the sub panel I will have to invest money in new GFCI breakers (One 20 amp and one 30 amp) at the sub panel and standard 50-amp breaker at the main panel. Before I do that I want to eliminate any other possible cause.

This morning I ran the sauna heater and has it heated up I could turn the thermostat down and shut the heater off without tripping the GFCI breaker. After about 10 minutes when the heater reached maximum heat output turning the thermostat down to shut off the heater caused the GFCI to trip. I repeated this same scenario three times with the same results.

Just after the GFCI breaker tripped I tested for any leakage to ground on either leg of the 240 circuit and found non.

Does the capacitance on the long run from the main panel to the sub panel increase with time as the elements of the heater heat up causing increasin resistance?

Moisture in the cable can increase the capacitance of the cable.

Thanks again


I'm going to try your suggestion. Will let you know the outcome.

Bill

OK It also increase the leakage milli-amp current on such a long run, so moving the breaker should work.