Try this.Any idea why the gfci would trip when the spa motor is turned off? Will start and run. Trips when motor is turned off. Can anyone think this one further than me?
Shouldn't the motor capacitor absorb this spike?Try this.
The collapsing magnetic field of the motor is sending a spike down the line.
This spike (with a high frequency edge) is capacitively coupled into the electronic circuitry of the GFCI,
causing a mis-read of the 'balanced' state of the hot/neutral current picked up by the sensing toroid.
Try putting a light-bulb on the circuit to maintain an alternate path for the spike.
Just a thought.
Possibly, but if it is a capacitor start, then the cap will be switched out of the circuit.Shouldn't the motor capacitor absorb this spike?
If you used a Electric Fast Transient generator to test you get very repeatable results at tripping GFCI's.101214-0756 EST
I have tested a Leviton 7899 GFCI with a crude transient generator, an AB #2 motor starter, rapidly and randomly actuated, and been able to trip the GFCI. It does not easily trip, meaning the probability is low, but possible.
In general I consider the 7899 relatively immune to transient tripping. However, looking at their circuit board layout I can see an easy change that might further improve its immunity.
Have you tested your theory or is it all speculation?101214-1100 EST
The problem area I see on the Leviton board is a somewhat long trace from pin 1 of the LM1851 to the SCR gate. No resistor in the trace path and the shunt capacitor is at the 1851.
The capacitor C2 should be moved to a spot immediately adjacent to the gate and cathode terminals of the SCR. Then a small resistor, maybe 1000 ohms, should be in the trace from the 1851 to the SCR gate, and adjacent to the SCR gate. This would reduce stray capacitive coupling to the SCR gate.
This particular problem area has nothing to do with the inverse trip time characteristic of the 1851.