GFCI failure -- mystery...? - Page 2

beepbeep · 02:18 PM

I have one GFCI breaker feeding the whole house (3-phase 380/220V feed rated at 25 amps) ...GFCI is rated at 30mA which is "life injury protection"-class...what they calculate is highest current still giving you chance of survival.

It started tripping once. My first knee-jerk reaction was "#@!! GFCI is broken! I'll buy a new one". Which I did....same problem. Then it was "damn !@@@# GFCI, it's just a nuisance, I should bridge it". Fortunately, I came to my senses and took some time troubleshooting the leads with Ohm-meter. Of course, it wasn't the GFCI's fault...an 220V outlet was incorrectly installed during the kitchen remodel (wire too long) . Once plug was inserted, it shorted the pins between earth and neutral. Some of current went through earth and GFCI tripped. As it should. Without GFCI, I would never know this.
Outlet fixed = no more problems.

If GFCI trips, there is current flowing through protective earth lead. Alas, something is wrong. Find out what is wrong. Don't shoot the messenger.

The Youtube clip with guy drowning the radio into the sink is pure nonsense. He obviously doesn't understand how it works. As long as water in the sink is isolated from earth, it won't trip the GFCI no matter what he drowns in it as there will be no current flowing through earth.

But the moment he puts his hand in the water he better pray GFCI works and is rated low enough not to kill him.

imcarthur · imcarthur's Garage

Quote:

Originally Posted by beepbeep

If GFCI trips, there is current flowing through protective earth lead: something is wrong. Find out what it's wrong.

^^^^ this. Especially since it has been replaced. There is some fault. Possibly intermittent - just to drive you crazy.

Ian

Rusty Heap · Rusty Heap's Garage

GFI's are needed?

Depends on year of home build, or permitted re-build, and codes at the time.

Codes get more and More anall all the time.

I believe present UBC and NEC NFPA79 code is any outlet, within 3 feet of in-house water source or sink/shower, or anything outdoor, or even in a garage/shop/out-building, needs a GFI

YMMV, IMHO, interpetation of code may apply.

Electricity is not to be messed with, nobody wants to be injured, burned, or house fire.

look 171 · 03-01-2013, 08:43 PM

around here, all kitchen outlets now. it use to be 3'. arc fault through out (at least on my current job)

djmcmath · 03-02-2013, 09:26 AM

Quote:

Originally Posted by imcarthur

Possibly intermittent - just to drive you crazy.

Ian

Yup. I had time to play with it this morning, so I went down to check the breaker. It reset just fine, and I've been using it with power tools all morning. If it works, I can't troubleshoot. Grr!

djmcmath · 03-02-2013, 09:28 AM

Quote:

Originally Posted by Rusty Heap

Electricity is not to be messed with, nobody wants to be injured, burned, or house fire.

Yup, this is an outlet in a bathroom that'll be right next to the sink. It's a small bathroom, so it's pretty much within 3 feet of the shower and toilet, too. :-/ So it kind of has to work right, imho.

djmcmath · 03-18-2013, 04:27 PM

Ok, it finally tripped again, and wouldn't reset. I waited until Saturday morning (home during daylight) to swap the GFCI breaker for a normal breaker. Then I swapped the receptacle in the bathroom for a GFCI receptacle.

It's been working great for a couple of days now. I'll report back in a month. If it's still working, the big question is "why?"

Thanks,
Dan

1990C4S · 03-18-2013, 04:57 PM

If you have leakage between the breaker and the outlet then what you are seeing is expected. The ground fault receptacle won't see leakage upstream and it will be fine.

I would check from the panel with an ohmeter and a megger if necessary.

djmcmath · 03-18-2013, 05:15 PM

Quote:

Originally Posted by 1990C4S

...what you are seeing is expected....

Expected? Ok, that's good. Or bad. Translating this to non-electrician: if there's a small ground between two phases somewhere in the line, it'll force a breaker to trip, but the outlet will be fine. ? Better question: if I have a ground on the line small enough that it doesn't trip anything, is that safe? Or is the fact that it trips a GFCI breaker an indication that the wiring is unsafe?

Quote:

I would check from the panel with an ohmeter and a megger if necessary.

Ohmeter checked fine. I don't own a megger. :-/

1990C4S · 03-18-2013, 05:25 PM

I think you have leakage between the breaker box and the outlet.

If it were mine I would ignore it, unless it was practical to replace the wire.

djmcmath · 03-18-2013, 05:35 PM

Quote:

Originally Posted by 1990C4S

If it were mine I would ignore it, unless it was practical to replace the wire.

Haha, it was practical to replace the wire about 3 months ago, before I hung the drywall. Murphy says that wiring problems don't happen until it's hard to replace the wires.

Thanks for the wisdom; I'll quietly ignore the problem.

john70t · 03-18-2013, 06:06 PM

Quote:

Originally Posted by beepbeep

It's quite easy to troubleshoot. Break the circuit, remove the breaker and measure leads going FROM GFCI with ohm-meter. Resistance between earth, phase and null should be very high, almost infinite.

Excellent post.

However, one thing to remember is:
An OHM meter (AKA handheld DVOM) has very delicate internal circuitry, and uses micro-amps through a wire to test resistance.
All powered by a small 3-9V battery power supply.

If there is a partial screw puncture (with 110V arcing), this may not "close" the short using a low voltage test, and may return a false negative of a short.

wdfifteen · wdfifteen's Garage

This reminds me of this thread

http://forums.pelicanparts.com/off-topic-discussions/625195-what-chances.html

billybek · billybek's Garage

A good quality meter will do 6 meg ohms and should be enough to give you an idea if you have a leak to ground. A decent megger will put 500 vdc on the circuit looking for leaks to ground or neutral.
Maybe to be safe try an arc fault breaker on that circuit and leave your gfi receptacle in play.
Just thinking that if you did have a small shunt to ground or neutral an arc fault breaker may keep your house from burning down.

john70t · 03-19-2013, 06:58 AM

Quote:

Originally Posted by djmcmath

Ok, it finally tripped again, and wouldn't reset. I waited until Saturday morning (home during daylight) to swap the GFCI breaker for a normal breaker. Then I swapped the receptacle in the bathroom for a GFCI receptacle.

It's been working great for a couple of days now. I'll report back in a month. If it's still working, the big question is "why?"

Thanks,
Dan

An outlet GFCI is at the end of the chain. Local protection.
A breaker GFCI at the beginning and looks at the whole circuit.

Still not ruling out there could have been a fault with the outlet or the breaker, but it sounds like a wire has been punctured.
A normal circuit breaker may not be sensitive enough to trip the whole circuit, given a partial short.

Although this tool is expensive, it is cheaper then the alternative:
Amazon.com: Short / Open Circuit Finder and Circuit Tracer - Supersedes SHFFF300: Everything Else

djmcmath · 03-19-2013, 01:50 PM

Actually, it would be cheaper to re-route the wire, I think. It'll be some holes in the drywall, but I can do that. If there's a real risk of eventual house fire here, I don't think there's much option.

imcarthur · imcarthur's Garage

Quote:

Originally Posted by djmcmath

Actually, it would be cheaper to re-route the wire, I think. It'll be some holes in the drywall, but I can do that. If there's a real risk of eventual house fire here, I don't think there's much option.

A very good plan. You know there is a problem & we ALL know that you don't mess with electricity. Replace the line.

Ian

911SauCy · 911SauCy's Garage

Knowing this is looking through a different glass all...

But. I wish I had a GFCI that was more sensitive or just worked in college. My dorm room went up in flames at UConn my Junior year bc of a faulty GFCI.

I woke up at 2am in a lofted bunk choking down black smoke...not kuhl!