GFI keeps tripping

[whytes]

My home is 6 years old. The garage has a GFI outlet and two other outlets tied into it. In addition, there are three outdoor outlets tied into the same GFI. I have my irrigation controller plugged into the GFI. I have low voltage lighting plugged into two of the outdoor outlets (44 W transformer and 200 W transformer - using 70 Watts). In August, I installed two post lamps (200W with a photoeye) at the end of my driveway. I ran a approx 130 feet of 14/2 direct burial cable, partially direct burial, partially through plastic conduit to one of the outdoor recepticals for power. I installed a switch between the power and the post lamps at the outdoor receptical.

I had no issues until about 2 weeks ago, the GFI began tripping. Sometimes I can reset it and it will be fine for 2 days, other times it will trip every 10 seconds, other times it will be 10 minutes - random. The load is not changing during this time (ie two post lamps, low voltage lighting, landscape controller). I believe it has something to do with the post lamp run since when I turn them off with the switch, the GFI will not trip. I have checked all connections and they are good.

Any ideas? Could it just be a bad GFI? Could there be a break somewhere in the line that randomly goes to ground?

[HayZee518]

gfi

the purpose of the gfci is to interrupt power so there is a no hazard condition. it is an electronic circuit that detects current flow greater than 5 milli-amps and trips its circuit.
it measures the current in the black wire going through a load to the white and back to the source.
any imbalance as to ground [bare wire] will trip the receptacle protection.
if you had a drill motor that had an abraded field winding, chances are that the metal case could get charged to 120 volts - a dangerous condition. a gfci will trip if this condition is present.
look for abrasion where the cable makes a turn in a metal conduit. plastic conduit will not affect it. water or condensate in your fixtures will trip a gfci.
for the sake of argument, your run of 130 ft is electrically actually 260 feet - a black going out 130 feet and a whit returning at 130 feet equalling 260 feet. this is used in determining voltage drop.

[whytes]

gfi

Thanks for the info on the purpose and use of a GFI. Like I said, I checked all the connections and they are good (and dry). I used plastic conduit and only straight runs. Nothing else is on the circuit, other than what I described. And if I isolate the post lamp run of wire, using the switch I installed, the circuit does not trip. If it tripped immediately each time I reset it, I would know I had a short somewhere in the post lamp run of wire but like I said, sometimes it is fine for days before it trips. Could this be the GFI itself, could the long wire run be the cause? Or is there a break in the line somewhere that moisture is effecting? Do I need a heavier guage wire than 14/2? The photoeye? I would pull all new wire but based on the length and that it is buried, it would be a lot of work, so I'm looking for other ideas' first. Thanks.

[HayZee518]

gfi

since the load for the lights is the ONLY load on that circuit and not accessible by personnel, why not use a dedicated regular breaker circuit on that one line. the code definition for using a gfci is "protection of personnel"
if there was an outlet at the light pole(s) then I could see a gfci in either or both outlets there.
another thing is a photo-eye needs a constant supply of line voltage to run, otherwise, with the interruption of power each time you need the lights, the photocell goes through an internal "self check." if you wanted it switched then the switch should be between the load and the red wire, not the black.

[dfitz3390]

can you temporarily remove the photo eye from the circuit and try it for a few days ?

[HayZee518]

photocell

in the thread I was referring to a wired in photocell. a screw in photocell, I'm sure is what dfitz was talking about.