Pool light issue, what am I missing?

[Flex]

Pool guy I know calls and asks me to look at some 120v pool lighting. 2 lights in the pool. One is a larger niche light and the other is a smaller puck style light, but both 120v. Both lights meet at a common j box where the switches feed comes in. Gfci Breaker was tripping so pool guy changed out the lights. Gfci Breaker still trips so he calls me. I swap out for a new gfci Breaker, still trips. Do a ton of swapping around one light at time, no light, double check wirenuts, still trips. For the heck of it I put the feed on a spare 20a normal Breaker, now lights work. Now I'm confused. Put it back on gfci Breaker, as I have no intentions of using non gfci, was just a test. Take an LED light stand and a temp plug I have out of the truck and tie it to the switched feed with the pool lights disconnected. Light stand works. Gotta be at the pool. Pool guy is going to bring a niche light to hook up outside the pool but I think I already proved that. Anyone have an idea of what the gfci is seeing that the regular Breaker wouldn't?

 

[richie921]

Yeah, a ground fault. You're bleeding voltage somewhere. A GFI receptacle basically compares the current flow going out to the current flow returning. If they detect a difference of 5 milliamps or more it's going to trip. This can come from numerous things. If you had a bare ground in a pipe filled with water and a nick in the neutral insulation the voltage can bleed. Somewhere voltage is finding a parallel return path and the ungrounded and grounded conductors are out of balance. Can be anywhere downstream of the GFCI up to and including the lights.

Sent from my SM-G935P using Tapatalk