I have a circuit protected by a GFI circuit breaker that has failed. So far,
I eliminated anything plugged in or switched. Also determined that the
circuit is fine with a standard breaker and draws no current. So, I left it
this way for now.
Its impossible to check the actual wire runs behind the sheetrock. Is there
anything else to check as a possible source of the trouble?
If there is really no current, on a meter that registers milliamps, go
get a new GFI breaker, as the old one is crap. Or plug in the old one
with the wires disconnected and see if it trips. In either of these
cases, the breaker is the problem.
If no current is in fact "not quite no current" on a sensitive meter,
and the difference in "not quite none" is greater than 5mA when
measuring the hot leg .vs. the neutral leg, then there is an actual
fault. If nothing is supposed to be drawing current and something is
drawing a little, then you'd need to start running down the circuit to
see where that's happening (which section of wiring) by disconnecting
the wires at each device, moving away from the breaker, until you find a
place where no current is being drawn - then the suspects become the
device just disconnected, the device before it, and the wire directly
between. If things have recently been nailed or screwed in the that
section of wall, there's a suspect. If you have rodents, there's a
suspect. Etcetera. If you have a bad section of wire, the sheetrock
needs to get ripped open - but at least you can find out where it is, if
Not being a gung-ho electrician type, I do a lot of running back and
forth to the breaker box when trying to sort out something like this,
and suggest you do the same.
Is it possible there is another GFI on the same line? Like a GFI
protected outlet? My old shop had 2 GFI outlets on a single 120
circuit plus a GFI breaker on the 220 volt hot tub circuit. If I
tripped any of the three, all were tripped! Very frustrating until I
discovered the need to reset all of them when one tripped.
I had a GFCI that tripped intermittently, nor related to load or
anything plugged in or turned on. I spent a full day tracing wires,
un doing junctions etc.
What I found was that the NEUTRAL had hit the GROUND in a light
permanent fixture, even with the switch off, it would still trip the
That's a ground fault.
Keep in mind the trip is 4-5 ma. It doesn't take much to trip a properly
My list of the trouble makers (in order)
-GFI breaker getting fussy in it's old age.
-Moisture or fuzz growing in one of the outlets
-Moisture in the wire
Pull the wire off the breaker, see if it still trips. While it's off,
pull the neutral wire off, run an ohm check on black to ground. Anything
less than several hundred K ohms is suspect, 25,000 ohms will pop the
GFI. Disconnect everything on the circuit, same readings.
Karl Townsend wrote:
The one obvious thing that comes to mind is a short between
neutral and safety ground somewhere in the wire run. The GFCI
requires all current flowing on the hot must be exactly matched
by an equal current flowing oppositely on the neutral. If these
currents don't match to within a couple mA, the breaker trips.
You can pull the neutral off at the breaker end and use an
Ohmmeter to check for continuity between N and gnd. If it still
shows connected, pull all outlets and switches along the run and
look for a pinched wire. Only a GFCI would complain about such
a connection. If nothing shows up in the boxes, then you likely
have a romex staple through the cable somewhere! That rates a
On Mon, 3 Mar 2008 19:23:12 -0600, "Karl Townsend"
What's on the circuit? Is it something that is better protected by
a GFCI receptacle?
The long wire run adds a lot of inductance that can give you false
trips with big load changes, where it won't if the GFCI is at the
receptacle closest to the load.
I have a batch of pedestals on a dock we have to rework - 50 to 250
foot wire run with a photocell and magnetic ballast with a 7W PL lamp.
When the PCell /opens/ the inductive kick trips the GFCI breaker.
We're going to try a PF Correction (run) capacitor across the
ballast, as soon as someone at Advance figures out what size. If that
doesn't work, it's either electronic ballasts or LED lights.
--<< Bruce >>--
Thanks, everybody, for all the tips.
My plan: Buy new GFI breaker, new receptacles, and new light switches.
(Everything is 17 years old) I'll replace one at a time and test. Plus
inspect each box as I replace components.
I really hope this works. Tearing out sheetrock is not an option I'll
entertain. If it comes to this, I'll do as Bruce suggested and go with GFI
receptacles and a standard circuit breaker.
Quite true - but the problem usually lies in a fussy inductive or
capacitive load plugged in at the far end of a lot of wire. Or you
have an underground segment that has damaged insulation and water in
the conduit, and that should be changed out anyway.
When you are working in the Gardening Shed in the backyard and you
trip the GFCI receptacle you can reset it right there. You don't have
to stop what you are doing, troop a quarter mile back to the house to
the breaker panel and reset a GFCI Breaker or a master receptacle,
then troop all the way back out to the back fence again.
And the loads that don't need to be on the GFCI like the Malibu
Lights transformer (big inductive kick when that turns on and off) or
the Sprinkler Controller (transformer isolated too) can be wired in
No GFCI on the sprinkler clock, you hard-wire it ahead of any GFCI.
If it trips just as you leave for your vacation, you come back to a
lawn and shrubs and flowers and garden beds that have been bone dry
for three weeks, and everything is either dead or dying.
And you REALLY do NOT want a Refrigerator or Freezer on a GFCI
circuit EVER, no matter how much the fools at the NFPA want you to
make all kitchen convenience receptacles in new houses or major
remodels GFCI protected - make it a separate "Dedicated Appliance
Circuit" with a single receptacle and hold your ground with vigor if
they want it changed...
(Or you install a separate GFCI there to make him happy till after
the Final Inspection and/or Certificate Of Occupancy is signed. And
the minute the inspector is driving away you yank it back out...)
Logic: Not only do you lose the contents of the fridge or freezer if
the GFCI false trips, if the power has been off for weeks and you open
the door without knowing it's been off ahead of time and take radical
protective measures (like stuffing Vicks Vapo-Rub ointment up each
nostril) I can guarantee that you WILL lose your lunch.
The term "gag a maggot" is rather accurate. You'll end up buying a
new fridge, because that stink will NEVER come out, no matter what.
--<< Bruce >>--
You are correct. I assumed receptacles. If it's a 15-amp or 20-amp
115-volt circuit, then the run can be wired so the first receptacle is
a GFCI receptacle that also protects everything downstream of it -- or
not, depending on how it's wired.
GFI outlets actually work better than using the GFI breaker. If you have
any residual leakage upstream from the outlet, it doesn't add to the
trip current that the outlet protects against. Should be a big deal in a
residence, it can be a real pain in a barn or other similar place with
damp conditions and long runs.
Don Foreman wrote:
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