I recently installed a couple of receptacles on a fence for a customer. I extended an existing circuit. Being an old house, the circuit is ungrounded(does not have an equipment grounding conductor). The brand new GFCI is tripping. The following is the circuit…
Out of the house into a box with the GFCI. One pipe (EMT) up to the receptacle for the heat tape. (not protected by GFCI). One pipe (PVC) into the ground and across a path to the fence to the first fence outlet. Pipe underground from first fence outlet to second fence outlet. Pipe up from second fence outlet to timer.
THHN conductors , all new equipment, all new pipe, aluminum WP boxes with in use covers, wooden fence, brick house, two strings of new Christmas lights plugged into each recep on the fence. Lights are wrapped onto trellises made of copper pipe.
The tripping is apparently random, I’m not getting much help from the homeowner as far a description of the problem. We first thought it only tripped when it rained, but now that doesn’t seem to matter. It was tripping before I replaced a switch with the timer that is currently in the circuit, so it isn’t the timer.
So… got any ideas? I’m trying to make the call back(s) as short as possible.
If you haven’t drawn blood today, you haven’t done anything.
Replies
I'd ask the homeowner how often and what time of day the GFI trips (or rather, when do they notice that the GFI has tripped). Maybe at night, when the dew forms, there's enough leakage in the light strings to trip the GFI?
Maybe it's an overly sensitive GFI. I test the GFIs I install using a Sure-Test, a unit that tells me the trip current and time-to-trip. There's a good bit of variation among GFIs; some trip at 5 mA in 40 mS, and others at 7 mA and 170mS. There will be random variablility in the component values that influence trip current and time. I believe also that some manufacturers bias the trip point to the tight side (acceptable value is 6 mA +/- 1mA).
Anyway, to troubleshoot, if you remove the light strings and the heat tape from the circuit, and replace the GFI, and it still trips, it's time to megger out the legs of the circuit. Or, it may be simpler to pull new wire. Maybe there's a spot on one of the wires where the insulation was shaved bare during the pull. The wire may move close enough to part of the EMT to leak enough when things cool off (or heat up), causing the wire and pipe to move.
Or, it could be gremlins. The high voltage from the megger will usually drive the little suckers away...
Good luck,
Cliff
..where is the neutral of the heat tape receptacle connected in the box?
Quick question
Do you have a ground at the GFCI receptacle?
If not; I believe that your neutral would probably be floating, since you mentioned that the circuit had no ground coming from the panel.
Then the imbalance could be caused by anything else in the house turning off or on. (I call it "backlash")
If this is the case; you may have to ground the "feed" neutral. (not to be confused with the "load" neutral)
I did a service call on an MCC one time where the thing refused to work. It turned out that the neutral/ground bond had been disconnected, and the phase voltages were at 170/50.
It's a good thing that all the solenoids were on the 50V phase, or the company would have had to pay for replacing all the controls in this thing. And at 2am, I don't know where you could get replacements from. (If the MCC wasn't working, the place would have flooded, and since it was a phone company switching center, shutting down would have cost millions).
locolobo; Edmonton, AB
I was thinking the heat tape was going to be the culprit,
I have no idea what the setpoint on those resi tapes is and the thing may be cycling, since the weather has cooled !perhaps bosn should check the panel for a bond on the N instead of trying to ground it at the j-box,....
"
been a few years since I did this
trying to remember if GFCI requires a ground reference
in 15 yrs of wiring, the only time I had a problem with spurious tripping was when the panel was mounted so loose, the GFCI breaker popped every time the kid upstairs jumped off his bed. No other breaker.. just the GFCI. Hammerdrilled the backboard to the concrete, fixed that problem.
locolobo; Edmonton, AB
HAHAHAH, that will sure take care of it.
.I had to think before I wrote my post
I got used to everything BUT residential....and NO romex, I pull Grounds to everything anymore, so its a no brainer .
but the Neut. is what the GFI looks at and trips on a 2nd ground !"
Install those clear plastic covers over the outlets. That'll eliminate at least half the problem.
No electrons were harmed in the making of this post.
The heat tape is not GFCI protected. That part of the circuit comes off the joint ahead of the GFCI. The recep for the heat tape is not readily accessible and the 2005 code gives us this leeway now.
I was working with another journeyman today and posed this problem to him. He suggested that the Christmas lights may be leaking to the copper trellis and to ground. He said that since they are made so cheaply, and they are wrapped around the copper trellises, there could be enough path for leakage, especially with a little moisture.
I'm leaning toward the bad GFCI option. I want to go change it and have the customer keep a little closer track of the circumstances after I do that.If you haven't drawn blood today, you haven't done anything.
that's the nice thing about intermittent problems.......
....you end up tearing out everything, and if you try to megger those little lights....pooof....hehehehe, wasn't sure about the neut., just a guess after all ?"