GFCI Breaker Tripping Spa Light
I have a problem with GFCI breaker tripping on a Spa (hot tub) light. Here's the details.
This is a built-in spa (not premanufactured) built 20 years ago. There is a underwater Sta Rite (Pentair) enclosure built into the gunite wall. Installed in that niche is a Sta Rite 120 volt 250 watt fixture. The fixture is fed by a 16/3 captive cable that runs in a conduit from the niche to the equipment room on the other side of the wall. The 16/3 cable is connected via wire nuts in a jbox to 3 14 gauge stranded cables (black, white, green) in a conduit from the subpanel. The fixture is alone on a 20 amp GFCI breaker in the spa subpanel. The GFCI breaker trips as soon as it is set. Until recently, the light had been working fine. I swapped in a new breaker with the same results. Given that the fixture is 20 years old, I installed a new Sta Rite fixture. It also trips the breaker immediately.
I have tried a number of things to try and locate the problem but with no success. I took the new fixture and captive cable out of the spa and conduit and connected it directly to the breaker. That worked fine. With the fixture and cable back in place, I disconnected the ground wire in the jbox. The strange thing is that, with the ground wire disconnected, the breaker did not trip as long as the fixture was out of the water and not in its niche. As soon as the metal housing of the fixture touches the water, even slightly, the breaker trips. With the light fully installed back in the niche, one by one I disconnected the 3 wires in the jbox. With the ground wire and hot lead connected but the neutral disconnected, the breaker did not trip. The neutral connected by itself or the neutral and the ground connected caused the breaker to trip even without the light on. That tells me the fault is coming from the neutral. The problem is I can't imagine how the fault is occuring. It's a new fixture. The captive cable is new. There is nothing else on the circuit.