GFI keeps tripping even with nothing plugged in

[davewill]

The 120v garage circuit I've been using to charge my wife's Plug-in Prius is giving me problems. My wife came to me and complained that her car hadn't charged the last couple of nights. I investigated and found the GFI had tripped. After unplugging everything on the circuit, I found that the GFI would still trip, usually within 30s or so. I figured the GFI receptacle had gone bad and bought a new one. The new one is acting the exact same way. I'm not sure how to troubleshoot this further. I don't believe I've missed any outlets on the circuit. The breaker is clearly labeled "Garage GFI" and all of the bathrooms and outdoor receptacles seem to have their own GFIs and I haven't found any outlets that are dead.

The house is three years old, so the wiring is pretty new. I hate to have to call an electrician out to fix this. Any ideas?

 

[kennybobby]

What charger are you using? The Elcon/TCCH chargers are not isolated chargers and there may be some leakage current internally.

 

[Bangor Bob]

A damp garage (even just condensing levels of high humidity can do it), can cause nicked insulation to fail by saturating the paper inside the romex forming a bridge to the ground wire.

If it's tripping with nothing plugged in, something in the wiring needs checking out!

 

[davewill]

It's a pretty dry climate here. We did get some "high" (60%) humidity a week ago, but there certainly wasn't any condensation.

I guess I need to isolate wire runs and disconnect them one by one from the circuit until I find the one that's causing the trip? Luckily there are only three receptacles on the circuit and the other two seem to branch directly from the GFI receptacle. Any measurements to make to test or other possible causes to look for?

 

[dhrivnak]

Or you can just replace the GFI. I have had 4 fail in various places at home and have yet to have an issue with a normal plug. Not sure if I got a bad batch or is they are just buggy.

 

[MorrisonHiker]

Are you sure you checked all of the outlets? I had a similar problem years ago and replaced the GFI outlet. After hours of troubleshooting, I found that the GFI outlet in the bathroom (which I replaced) also served an outlet on the outside of the house. That outlet had gotten weathered and broken and was causing the issue. Once I replaced that outlet, the GFI wouldn't trip anymore.

It sounds like you've done troubleshooting but haven't tracked it down yet. I recently redid all of my outlets at my current house (upgrading to Decora/rocker style) and it was fun (NOT) trying to figure out why some of the living room outlets were hooked up through the garage...and upstairs outlets were on the "basement" circuits. Don't always believe the labels! I can't tell you how many dozens of trips I made to the main panel to turn off breakers!

Have you used a tester to confirm all of the outlets are wired correctly? Does the light on the GFI outlet illuminate correctly? Really old GFIs didn't have any lights. Older ones had red lights that showed when it tripped. All of the new ones I installed have green lights to show they are working and the light won't even light up if it isn't wired correctly.

 

[Chris TX]

It sounds like ground and neutral could be swapped on that outlet or another outlet with something plugged into it on the same breaker. If an appliance is plugged into a different outlet on the same circuit, it's going to put 120VAC neutral back through the ground wire and possibly trip the GFCI. Is this GFCI outlet daisy chained to another outlet?

 

[FlasherZ]

The GFI protects everything downstream of it and doesn't care about upstream. Does this GFCI have anything connected to the load terminals? Or just the line terminals?

If you have downstream connections on the "load" terminals, then you should disconnect them and try with only the car charger plugged into the receptacle. If it doesn't trip, then you need to look at the downstream wiring connected to the "load" terminals. It could be a number of things - nicked insulation on the neutral sending current back via ground through a metal box or water, someone "borrowing" the neutral on that circuit for another circuit or device (like lighted switches, occupancy sensors, etc.), someone "borrowing" the ground to operate an occupancy sensor or lit switch, etc.

If it does trip with only the line terminals connected and the charger plugged in, it's either the receptacle or the charger that's bad. Try swapping one or the other.

 

[Mike Ark]

Is the circuit breaker that feeds the garage also GFCI? If you house is that new it might be. I believe that I read somewhere that putting a GFCI outlet downstream from a GFCI breaker can cause problems like this.

 

[davewill]

Or you can just replace the GFI. I have had 4 fail in various places at home and have yet to have an issue with a normal plug. Not sure if I got a bad batch or is they are just buggy.

Already did.

Are you sure you checked all of the outlets? I had a similar problem years ago and replaced the GFI outlet. After hours of troubleshooting, I found that the GFI outlet in the bathroom (which I replaced) also served an outlet on the outside of the house. That outlet had gotten weathered and broken and was causing the issue. Once I replaced that outlet, the GFI wouldn't trip anymore.

It sounds like you've done troubleshooting but haven't tracked it down yet. I recently redid all of my outlets at my current house (upgrading to Decora/rocker style) and it was fun (NOT) trying to figure out why some of the living room outlets were hooked up through the garage...and upstairs outlets were on the "basement" circuits. Don't always believe the labels! I can't tell you how many dozens of trips I made to the main panel to turn off breakers!

Have you used a tester to confirm all of the outlets are wired correctly? Does the light on the GFI outlet illuminate correctly? Really old GFIs didn't have any lights. Older ones had red lights that showed when it tripped. All of the new ones I installed have green lights to show they are working and the light won't even light up if it isn't wired correctly.

Yes, I had the fun of having outdoor outlets daisy-chained off the GFI in my master bath at my last house. My wife used to occasionally lean her knuckle on the "test" button for leverage to pull the plug out on her hair dryer. I'd find out when my weed whacker wouldn't work outside. Pain the butt, since the master was on the second floor. OK, I'll add turning the breaker off and checking the whole property to see if there are any outlets dead that I didn't expect. I had only checked places I expected to be GFI. We did add a new person to the household and he might be using an outlet that didn't see much use before.

Unfortunately, the tester I have doesn't work if the power is off because the GFI tripped. I'll have to get a helper to reset the GFI while I have the tester plugged in.

The GFI protects everything downstream of it and doesn't care about upstream. Does this GFCI have anything connected to the load terminals? Or just the line terminals?

If you have downstream connections on the "load" terminals, then you should disconnect them and try with only the car charger plugged into the receptacle. If it doesn't trip, then you need to look at the downstream wiring connected to the "load" terminals. It could be a number of things - nicked insulation on the neutral sending current back via ground through a metal box or water, someone "borrowing" the neutral on that circuit for another circuit or device (like lighted switches, occupancy sensors, etc.), someone "borrowing" the ground to operate an occupancy sensor or lit switch, etc.

If it does trip with only the line terminals connected and the charger plugged in, it's either the receptacle or the charger that's bad. Try swapping one or the other.

Yes there are two outlets downstream of the GFI. Best I can tell they are each wired directly from the GFI box and not daisy-chained. Since it's tripping without the car plugged in, and the car is charging successfully plugged into another circuit that was luckily within reach, I've assumed that the EVSE and car are not the problem. The GFI itself isn't close to the car, but I could use an extension cord for a test.

Is the circuit breaker that feeds the garage also GFCI? If you house is that new it might be. I believe that I read somewhere that putting a GFCI outlet downstream from a GFCI breaker can cause problems like this.

Nope. I checked for that.

OK, troubleshooting steps as I have them now:

1. Make double dog sure I've identified all of the outlets that are daisy chained off the GFI.
2. Disconnect the load terminals to test the GFI receptacle itself.
3. Reconnect one leg at a time and try to isolate the problem.
4. Re-check the wiring of each outlet.

I really hope it's not a bad wire in the wall. That'll mean an electrician and money.

 

[FlasherZ]

Is the circuit breaker that feeds the garage also GFCI? If you house is that new it might be. I believe that I read somewhere that putting a GFCI outlet downstream from a GFCI breaker can cause problems like this.

That hasn't been the case for a while now, old GFCI outlets would do this but randomly.

- - - Updated - - -

Yes there are two outlets downstream of the GFI. Best I can tell they are each wired directly from the GFI box and not daisy-chained. Since it's tripping without the car plugged in, and the car is charging successfully plugged into another circuit that was luckily within reach, I've assumed that the EVSE and car are not the problem. The GFI itself isn't close to the car, but I could use an extension cord for a test.

OK, troubleshooting steps as I have them now:

1. Make double dog sure I've identified all of the outlets that are daisy chained off the GFI.
2. Disconnect the load terminals to test the GFI receptacle itself.
3. Reconnect one leg at a time and try to isolate the problem.
4. Re-check the wiring of each outlet.

I really hope it's not a bad wire in the wall. That'll mean an electrician and money.

You have a good plan.

I'm assuming those downstream receptacles are non-GFCI receptacles? If the downstream receptacles are also GFCI, then pigtail/splice them into the LINE side instead of the LOAD side.

ckt----LINE (GFCI-R) LOAD----------(non-GFCI-R)----------(non-GFCI-R)

or

ckt
|
LINE (GFCI-R)
|
LINE (GFCI-R)
|
LINE (GFCI-R)

Sometimes I find garages that have all GFCI's, yet the #2 GFCI is on the LOAD side of the #1 GFCI.

 

[davewill]

... I'm assuming those downstream receptacles are non-GFCI receptacles? ...

Correct, there's only the one GFCI receptacle.

 

[davewill]

Thanks for all the help. As it turned out, there were two outside receptacles that were also on that circuit. One of them ran a pump for a fountain that I allowed to go dry because of the drought. I thought I had unplugged it, but it was trying to run for a couple of hours each day. I assume the pump overheated and damaged itself. Anyway, it was tripping the GFCI.

 

[FlasherZ]

Thanks for all the help. As it turned out, there were two outside receptacles that were also on that circuit. One of them ran a pump for a fountain that I allowed to go dry because of the drought. I thought I had unplugged it, but it was trying to run for a couple of hours each day. I assume the pump overheated and damaged itself. Anyway, it was tripping the GFCI.

Great that you found it!

 

[Cottonwood]

Thanks for all the help. As it turned out, there were two outside receptacles that were also on that circuit. One of them ran a pump for a fountain that I allowed to go dry because of the drought. I thought I had unplugged it, but it was trying to run for a couple of hours each day. I assume the pump overheated and damaged itself. Anyway, it was tripping the GFCI.

Yours is a common GFCI annoyance. Whenever I have construction or remodeling done, one of my requirements is to never put slave GFCI outlets in another room from the master GFCI outlet. It costs a few more dollars for a few more GFCI master outlets, but saves frustrating mysteries like yours from happening.

 

[FlasherZ]

Yours is a common GFCI annoyance. Whenever I have construction or remodeling done, one of my requirements is to never put slave GFCI outlets in another room from the master GFCI outlet. It costs a few more dollars for a few more GFCI master outlets, but saves frustrating mysteries like yours from happening.

My home in California was the same way, although slightly different circumstances. They had taken GFCI receptacles in the bathroom and attached them to the LOAD side of a GFCI that was outside (which should never be installed that way). When I stacked firewood, I had thrown one a bit too far and it tripped the GFCI via the test button. It took me forever to find that receptacle that had disabled my bathroom.