delayed trip on GFCI


Old 02-02-11, 12:37 PM
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delayed trip on GFCI

I have a GFCI protected outlet in the garage, and the only items "downstream" (load side) of the GFCI are the outdoor house/driveway lights that are controlled by a photocell. This system has been working fine for a couple of years.

A few days ago I noticed the outside lights off, saw that the GFCI was tripped, assumed a nuisance trip, and reset it. The lights came back on.

About 5 minutes later the lights went out again. Reset. 5 minutes later the GFCI trips again.

Assuming a bad GFCI, I replaced the unit. Same thing. 5 minute delay and the GFCI trips. So, unlikely to be a bad GFCI.

I thought that one either has a ground fault or not, and if there is a ground fault, the GFCI should trip immediately or not reset in the first place.

What can cause a delayed trip, and what do I do about it?

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Old 02-02-11, 02:13 PM
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Only 1 outlet in the garage and its unused or possibility of addtional ones with maybe a second fridge or another item that cycle on and off like a fridge's compressor or defrost circuit?

or maybe dampness in the photocell optics
Old 02-02-11, 04:42 PM
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Disconnect the load wires from the GFCI and see if it trips? If not reconnect and disconect the line in from the next device and see if it trips. If not reconnect line in and disconect load out. proceed that way for all fixtures and photocells till you have determined which section of cable or device or fixture causes the trip.
Old 02-02-11, 05:48 PM
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@Epicman: There ARE other outlets (including one that a freezer is plugged into and two garage door openers) UPSTREAM (before, closer to the panel) than the GFCI outlet. There's nothing plugged into the GFCI outlet, and there are no outlets of any kind DOWNSTREAM (after, on the load side) of the GFCI. The only thing on the load side of the GFCI are the outdoor lights operated by a photocell (6 lights controlled by one photocell).

@ray2047: Although I didn't physically disconnect the load wires, the load wires are "implicitly" disconnected during the day because the photocell doesn't energize. If I reset the GFCI in the morning, it does NOT trip all day. It trips shortly after the photocell energizes the lights.

I'm sorry if I'm being dense here, but I don't understand what you mean by "reconnect and disconect the line in from the next device and see if it trips". Obviously, if I disconnect the line in TO the GFCI, it can't trip. By "the line in from the next device" do you mean the next device AFTER the GFCI (that is, what's connected to the load side of the GFCI)? From the GFCI load side the next device is the photocell, and after than, 6 outdoor lights.

Question: before I installed the GFCI, the outdoor lights were NOT GFCI protected. I could still have the GFCI protected and connect the photocell and outdoor lights to the LINE side of the GFCI rather than the LOAD side. Then, I'd have the same situation as I had before installing the GFCI. It would certainly solve the tripping problem. Am I courting trouble this way?

Thanks to both for your responses. I appreciate it.
Old 02-02-11, 06:43 PM
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Ray was just trying to break the circuit down into sections to see where the problem was coming from. Since the GFI is the second to the last item on the circuit there is little need to do this.

Exterior lighting does not require GFI protection unless called for by the manufacturers instructions.
Old 02-02-11, 09:07 PM
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Thanks much. I think in the short run I'll just wire the outside lights to the line rather than load side of the GFCI receptacle. Sometime when I have more time I'll do the more time-consuming job of finding all the junction boxes downstream of the GFCI and take the various circuit legs apart so I can try to isolate where the intermittent ground fault is coming from.

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