GFCI breaker trips on separate circuit

Aug 1, 2013
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New member here with an interesting GFCI situation. I have a shop with new fluorescent lights installed. The shop is fed from a 100 amp breaker located at one of the house 225 amp panels. the shop panel (four wire feed from the house panel) has four circuits one of which is a stand alone circuit for the lights only. lights are three wire 120vac wired correctly and everything is connected via emt--all surface wiring. No gfci circuits in the shop and the 100 amp breaker feeding the shop is not gfci.

At the house panel where the shop power originates there are several GFCI breakers one of which supplies a garage door opener circuit. Two openers (Wayne Dalton I-drive with feedback to turn on lights on a pair of outlets on the door opener circuit). So the I-drive units obviously 'talk' to the circuit they are on. I stress here that the opener circuit is entirely separate from the breaker that feeds the shop except of course they have a common main bus--they are in the same panel.

When I turn the shop lights on the GFCI breaker that feeds the opener circuit trips. this happens every time. I have checked the resistance of the opener circuit (wires disconnected from the breaker) and with both openers plugged in the meter reads 202 ohms. As I said the gfci will trip everytime the lights in the shop are turned on 50' away. None of the other 7 GFCI breakers in the panel trip--only the breaker with the I-Drive openers on it. I disconnect either of the openers and get a reading of 101 ohms on the open circuit resistance test and in this condition the gfci will not trip. Makes no difference which opener I drop off the circuit--having only one opener on the circuit works fine. plugging them both in at the same time and things go to pot.

I understand ground trickle associated with the lighting in the shop. there are 12 lights so I assume there is a fair amount of leakage to ground via the ballasts. my assumption here is that the combination of the ground trickle, inductive load at startup, power fluctuation at startup and the internal electronics of the openers is impacting what the GFCI on that entirely separate circuit is seeing. the I-drive opener circuit is the only circuit that has the 'feedback' component.

It is interesting to note I have read matter of fact comments here and there that say such a condition is impossible (GFCI trips on an entirely separate circuit). Well, that is not entirely the case since it is happening in my situation. It goes to prove that under certain conditions some pretty weird things can happen and do happen.

I have gone a bit nuts working on this one and have decided to just replace the GFCI breaker with a standard breaker and be done with it. I do nee BOTH doors working at the house.

Thanks, Catseye


Mar 2, 2014
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B.C. Canada
I will give you my best guess without heading over and taking readings. The GFCI is intended to trip it there is a sudden variation in current. Even though the GFCI is in the house and the lights are on a completely different circuit, they are effectively connected together in the breaker box. I am guessing 12 lights, 12 ballasts? All would draw a fair amount of current as you turn on the switch. You might notice that the lights in your home dim briefly when the shop lights go on. Because a GFCI is sensitive to this, I think this may be the reason - one short current surge. Options would be to install a surge suppressor between the house and the shop (which might make it take a little longer to turn on the lights). Alternatively to could control the lights with two or more switches - turning on one bank at a time - to reduce the surge.

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