GFCI Trips

[Hotwheels44]

I am hoping to find some help with an annoying problem. I am a lanscape contractor not an electrician. An electrician installed GFCI direct from panel and to transformers. I simply installed the landscape lighting from that point forward as I have done many times before. The boxes are hard wired and I took my 10ga low voltage wire from there. I have been called back to the job twice after heavy rains for breaker tripping. I did not think that low volt wiring could trip gfci. Could it be water in the light fixtures as some are pointing straight up into trees? The home owner bought his own lights from Home Depot. GFCI only trips if it rans heavily or for extended periods of time. I am inclined to believe it is the lights not the wiring. All my connections are always done with waterproof wire nut connectors (overkill) AND the end of my run also is covered again with waterproof connectors. Why is this breaker tripping? Could I just replace the GFCI with a normal breaker? If it was my wiring, I would imagine it would blow every time it turned on not only after heavy rains. Any suggestions would be greatly appreciated. Thanks.

[sitelights]

I direct your attention to two related threads on this topic: "Trouble shooting breaker" and "GFCI & Covers"; these appear directly below your post on the "Control Systems" forum.

The "search" at the upper right of your screen is a link the the site's search function; the word "GFCI" will take you to all of the citations on the site.

[Hotwheels44]

I am sorry if I am coming off as an amature but I did in fact check these threads prior to posting. They all direct their problem to plug in points. My application has a gfci directly on the panel running to the hadco transformer direct. No outdoor plugs nor are their any other items on the GFCI, it is a dedicated line just for the transformers, 3 to be exact. No one mentions the actual low voltage portion of wiring being able to cause an interrupt. Low voltage wiring isn't even required to have waterproof connections, which I did use anyway. I am trying to reach a decision that the problem is not mine. All I installed was from transformer out. No one seems to discuss problems with that area of the application rather problems prior to transformers. Thanks.

[sitelights]

Bad lamps, bare wires, dead shorts, etc. on the secondary (12v) side will not trip a GFCI breaker or receptacle. If your Hadco transformer has circuit breakers on the secondary side these will trip first; if there are no secondary breakers, there is normally a thermal, auto-reset internal breaker on the primary (120v) side. A fault in the low voltage system stops at the transformer. In the worst case scenario, when the transformer has NO built-in protection (such as buck and boost transformer), a dead short on the 12v side can burn the insulation off of the low voltage cable resulting in arcs, sparks and fire.

You did not state the total load on the three transformers; if the total load exceeds 12 amps (15 amp circuit derated) you are in harm's way. Watts divided by volts equals amps therefore if your total load is above 1400w you will have to add a second dedicated circuit to split the load.

I do not advise hardwiring a low voltage lighting transformer on the exterior since it could not be turned off to service (changing a defective photocontrol for instance) without going to the panel. If you cannot power down the device (by pulling a plug for example) your installation is not NEC-compliant. It is worth the few extra dollars to mount an outdoor receptacle with a raintight-in-use cover so that you can safely service the system

What I would do would be to unplug my transformer and, using an extension cord, plug it into a different circuit. If it does not blow the alternate circuit, the problem is in the original circuit. In your case, you should disconnect the panel GFCI circuit at the transformer and wire in a plug which could then connect the transformer via an extension cord to an alternate circuit. If the alternate circuit trips the problem is in the transformer; if it holds, the problem is in the original GFCI circuit or the hardwired point of connection to the transformer. Moisture or a loose or nicked neutral at that point could cause nuisance tripping in wet weather.