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GFCI trips when dimming incandescent C7 bulbs


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I have several strings of incandescent lights on my house, and was testing them out with the LOR Hardware Utility (v3.11.2 basic plus) before installing all of my lights, just to make sure things are working ok so far.


The controller is a CTB16PCg3, and I can use the HW utility to turn all of the incandescent (not LED) bulbs on without a problem.  The following works:

- Steady ON at 100% is ok

- Shimmer ON at 100% is ok

- Twinkle ON at 100% is ok


My problem is that when I use Fade 0% to 100%, my GFCI will trip every time.  I tested this channel by channel, and found it only happens for one specific channel, the lights on my roof.  And only if they are dimmed (steady on, shimmer, and twinkle are all Ok.)  None of the other strings of lights on the other channels trip the GFCI.


On the advanced configuration tab, the Dimming curve configuration is set to LOR Standard, since they are not LED bulbs.


I have left all of the lights ON at 100% for several hours without a trip, and only have a problem when dimming.  The problem also occurs when I try to use a sequence that dims the channel with the lights on the roof.  Will have an electrician out tomorrow to help troubleshoot the GFCI, but wanted to check here for suggestions since the issue is only specific to dimming and not flashing or leaving the lights ON.


I also tried using a different controller box (also a CTB16PCg3), since I have 3 controllers but so far am only trying to test out 4 channels.  I had the same issue with the 2nd controller - GFCI trips when dimming the lights.


It has not rained, and nothing is wet.  Nothing other than the LOR box is plugged into the GFCI circuit.  The bulbs are C7 size, and new - just installed by the local fire department today, so I doubt the lights are defective. However it is possible, I'm not ruling that out.  I just want to rule out everything on the controller and s/w side, since the controller is easily accessible without climbing up a 24' ladder.  :)


Not sure if that's enough information to make suggestions, but I hope so.  I'm new to LOR this year, so have little experience troubleshooting issues.  I'm definitely worried though, because I only have a few strings of lights up and no LEDs yet, and am already experiencing some flaky behavior.  I'm hoping this won't balloon into a nightmare when I get 48 channels up and running...!

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Shouldn't be tripping GFCI receptacles just because you are dimming or ramping, unless you have too many plugged together. Assuming you don't, here we go:

GFCI's do go bad, especially if it's very old. The newer ones are much better quality. We even sell some designed for outdoor use now. Make sure your electrician uses a GFCI tester to manually trip it. My guess is it won't pass the test. The outdoor rated GFCI's are only a few bucks more than the old style ones. I installed 9 new ones before last year's show and had the best year ever of no nuisance tripping.

Also, if the GFCI checks out, the next thing is most likely your lights. My guess is you have them base down. This looks great but can hold moisture in the socket. Almost impossible to find the one or ones that are not draining properly. They get bugs and dirt clogging the drain holes. I know you said no rain, but even humidity can trip them. Even if the GFCI tests good, since paying for service call, still would be cheap enough to just change it out anyway.

Good luck & hope you can get it fixed.

Edited by Mega Arch
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Hi everyone,

First of all, I'd like to thank you all for the suggestions! I have been very impressed with the LOR community, and the willingness to help with troubleshooting issues. I also heard back from the LOR help desk with some ideas to test just to make sure the controller unit isn't feeding current back during the dim cycle.

Ok, on to the results. Did the troubleshooting the help desk suggested. Basically, unplugging everything but the problem circuit and moving it to other channels on both sides of the controller, and so on. Haven't had a chance to follow-up with them yet, but am currently assuming all is well with the controller (which is brand new, so you would tend to assume it would be ok.)

Max-Paul asked if the lights were perhaps on the gutter. This is something I was slightly concerned about, but like the controller the lights are new, so I was hoping they were not the real culprit. That being said, yes, about half are attached to gutters and the other half are on the roofline shingles. So, there is a possibility for the gutter to be electrified and trip the GFCI, for sure. But, it hasn't rained since the lights were put out, so I was hoping they were fine. Also the bulbs are installed basically perpendicular to the house (sort of sticking straight out), parallel to the ground, so if it does rain, I assume the sockets can drain sufficiently to dry out.

So, the electrician...it was a long day! All day was spent examining wiring. No issues found at the breaker panel. Two outlets found improperly wired, with one wire simply resting on the terminal completely loose and not attached/screwed down. One of these was on a GFCI test/reset plug, but that plug was deemed ok, just the wiring needed to be properly attached. One outlet was physically broken in half - no idea how that would happen, but has likely been that way since the house was built! And, another GFCI plug (with the test/reset button) was faulty. The two outlets with bad wiring were fixed, the broken one replaced, and the last GFCI outlet was replaced.

Oh, and I found a faulty extension cord too (frayed, possibly gnawed by squirrel or rabbit). Cord was replaced.

After all that, the lights dim fine without tripping the plug. I'll post another update in a few days once I get a few thousand lights out there and put a little load on the new / repaired plugs. I'm optimistic that things will be ok now, and hopefully I won't have any more issues, at least not with the plugs.

Again thanks for the help. An emotional roller coaster for me - excitement to dismay - to not wanting to even try for fear things would never work because of the plugs tripping all the time - back to excitement again. :)

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Glad to hear that this lead to fixing of many problems that could have caused more problems down the time line. As for me asking about the lights and the gutter. There is always a chance for the metal to act as a plate on a capacitor. Thus a leakage current could have been the problem. Sorry dont want to be a wet rag on your parade. But you HAVE TO UNDERSTAND that GFI though are wonderful for saving lives. ARE a pain in the arse. Now if you have any wires on the ground and if you have any of those tomato case mini trees. I predict you will have more issues with the GFI tripping if it rains and you have either standing water or just very soggy ground. Will tell you this now so you are prepared with knowledge of how to fix it. Tomato cages, do not use wood, but .5" PVC pipe cut about 8" long and one end at a angle to help with hammering into the ground. At the flat end drill a hole or two for wire ties. Hammer 3 or  4 of these into the ground and place tomato cage on top. Zip Tie cage to stakes. What happens is that the wire tomato cage is touching the ground. The hot wire of your lights are capacity coupling a leakage current to ground through the cage. One mini tree might be enough. But several will add up the leakage current to trip the GFI. Same would be for wires on the ground. Back several years ago. One guy had it so bad he had to put stakes in the ground to raise all of his wires up and out of the standing water. Again do not use wood. Wood is only good if it is going to stay dry. Use cheap PVC piping.

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Just a quick update: Happy Thanksgiving everyone, by the way. I've been out stringing lights the last two days, and no mystery trips on the GFCI. I'm not sure on the light count, but I probably have half my lights out now. Going to keep loading things up and see how it goes. So far only have a couple of cords on the ground, and no plugs on the ground, and everything here is still dry. My props will have cords on the ground, but the ends will be at least a foot off the ground so they won't be lying in water, even if it rains.

Haven't made any mini-trees for my first LOR show, even though they seem to be a staple. I've read too many posts about ground fault trips and those things. Not sure if I'll attempt them next year, probably depends on how things go this year. Just want to get a successful show season under my belt. All my props are built with plastic or PVC with lights wrapped around them, so hopefully that will help.

I may try to run my cords in a PVC pipe to keep off the ground, and perhaps more importantly to keep the neighborhood rabbits from chewing them up. I had plenty of experience with that last year, and let me tell you, a chewed up cord will trip the GFCI all the time, especially if the ground is wet! I'm wondering if they are run in a medium sized PVC pipe, if the rabbits won't bother trying to chew thru it to get to the cords...anyone try this in the past? I don't care if the pipe isn't very attractive. I just want to avoid giving the rabbits more cords to snack on this year.

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