Troubleshooting GFCI Outlet Tripping

Question

Recently, the GFCI outlet that "powers" our back patio has started tripping. Initially, I thought the outlet was old since this only started recently (and we use our patio regularly), so I replaced it with a new one, but it still trips -- sometimes within seconds, sometimes after 10 minutes or so.

Downstream from the GFCI are two outdoor ceiling fans and three standard outlets. I've unplugged everything from the outlets and switched the fans and lights on the ceiling fans off. However, the GFCI still trips.

All three outlets + GFCI outlet have bubble covers on them.

Wiring runs like this:

Breaker --> light switch (inside) --> GFCI outlet (outside) --> 3 outlets / 2 fans

(All outdoor wires are run through PVC or metal conduit.)

At this point, my guess is that I have a short somewhere. Question is: is there a best way to troubleshoot this? I'd rather not have to take down the fans to determine if they're the cause, but if that's what I have to do, so be it. Also, is there an obvious reason why the trip sometimes happens immediately but sometimes after a few minutes?

My plan is to disconnect the load lines from the GFCI and see if it still trips. My assumption, however, is that it won't and I'll have to work down the line to see where the fault is.

Answer 1

First, a GFCI is designed to warn not of short circuits, but of leakage (a "small", but potentially fatal, current flowing from the hot wire to the metal shell of an appliance). By tripping, it is warning you that an appliance, either directly wired into the downstream circuit or plugged into that outlet or an outlet downstream, has a ground fault, i.e. leakage.

It may take longer for a small ground fault to trip the GFCI. Another reason for the delay may be that a motor is turned on or off, since that can cause an inductive surge, erroneously tripping the GFCI.

The easiest way to find where that leakage occurs is to disconnect one item at a time, starting at the distal end, i.e. the fans. First switch them off, reset the GFCI, and wait to see if that fixes the issue. If that does not stop the tripping then shut the mains circuit breaker, open the fan junction boxes and disconnect them (put a wire nut on the dangling hot wire), close the mains breaker and retest the GFCI.

If removing everything after the GFCI does not prevent tripping, then water may be getting into the outdoor outlet or junction box, causing the issue.

Once you find the item tripping the GFCI, check if water is getting into it, rather than assuming the appliance is defective.

Answer 2

Breaker --> light switch (inside) --> GFCI outlet (outside) --> 3 outlets / 2 fans

It is either the GFCI outlet itself (doubtful, because you replaced it) or one of the 3 outlets or 2 fans. "10 minutes or so" isn't the greatest for troubleshooting, but not too bad. Your choices for troubleshooting are "one at a time" or "binary". I would go for "binary" if you can. This is also "divide and conquer".

• Find an (approximate) midpoint if there is a chain from GFCI to the 3 outlets and 2 fans, and disconnect the wires there and see if the problem still occurs. If it does, then you know which 1/2 has the problem (unless there is more than one problem!) and can divide further.

or

• Disconnect (and cap for safety with wire nuts) wires going to 1/2 the devices and see if the problem still occurs. If it does, then you know which 1/2 has the problem (unless there is more than one problem!) and can divide further.

Which method will be easier depends on whether the devices are in more of a "chain" or a "star" configuration.

Answer 3

I came across this question when troubleshooting my own intermittent GFCI tripping issue with similar symptoms, and ended up having a novel solution; hopefully this answer saves someone else some frustration.

The GFCI detection mechanism is incredibly sensitive, and it turns out that RF signals from a "smart" water meter that reports usage over wireless can cause enough of an imbalance to make a GFCI outlet trip, as shown in this paper from the IEEE. In my case, the antenna on a recently replaced water meter was mounted on a shared wall between the garage and utility room, directly behind a GFCI outlet that then started intermittently tripping. After repositioning the antenna to be as far as possible from the outlet, the intermittent tripping stopped.

Answer 4

GFCIs can trip if they do not see ground or the load or the supply lines are reversed in polarity. Remember,GFCI stands for Ground Fault Circuit Interruptor. There may be a poor ground or no ground at the fans or outlets.in my experience with GFCIs, they can be very sensitive to ground issues.