ECN Forum Forums General Topics of the Trade General Discussion Area tripping gfci receptacle

this one is new to me. i have a situation where there is a GFCI receptacle protecting an underground feed to a flood light. Light is a simple 500W quartz.

Installation was done about 1.5 yrs ago, no problems. Now in the past month, the following as begun to occur.

when the light gets turned on, it will work for about 30-45 mins then trip the gfi.

the line from the gfi to the light is fine. i'm guessing a bad fixture. But why will it work for 30-45 mins?

anyone seen this before?

Possible ground fault as the fixture heats up and something expands. If the fixture is deenergized for 20 minutes, does it run for another 30 minutes or so, and then trip again?

LarryC

I have run into this before.

Aboveground NM, the box behind the luminaire had a little water in the splices. Dried it out, sealed the back of the fixture to the building, problem solved.
In another case, the UG feed had a little slice on one conductor in the UG part. Only tripped when the tide came in.

If your run is totally dry, try to isolate the problem by bypassing the UG feed with a temporary aboveground feed.

What type insulation is on the wire you used to feed the UG to the luminaire? THHN or THWN? or did you use UF?

Do you have a hi-pot? Some part of the circuit has a "slow leak".