I have a customer for whom I installed four Kichler 15732 LED uplights in his yard August 2010. He is happy with the lights except that (coincidentally I think), his GFI trips intermittently. I checked the system for shorts and couldn't find any. It's a 10 year old Unique transformer with a fuse, and the fuse does not blow. It's just the GFI tripping. I concluded that the had to be either the GFI itself, the line voltage side of the transformer, or maybe some other device on the same circuit with a big power demand turning on at the same times as the lights. I think what I am going to do is take a spare transformer over and temporarily replace his (I have a Vista MT on hand I think.) What would you do? What about the notion of something else on the circuit that turns on at night? He doesn't seem to know what else is on it.