Device tripping gfci

[arfrcchic]

I'm trouble shooting a gfci circuit for a friend. I followed the wiring around, isolating each receptacle. I got to the last receptacle and it seemed to just go away. It was holding with no load (previously it wouldn't hold at all). When I plugged all the appliances back in, that they had originally plugged in, their water cooler tripped the gfci. The water cooler has a grounded plug but all the other devices do not. It holds with everything else but the water cooler. So I tried a different appliance (steam cleaner) that had a ground plug to see if it's the device or if its the gfci circuit wiring. It held with the cleaner running. It's still holding.

So...two questions:

#1- the fact that originally I had the circuit tripping and I had a resistance reading between hot and neutral...then that just went away by the time I got to the last outlet. Was puzzling but now it's holding. Could it just be a fluke?

#2- The water cooler doesn't trip any other non-gfci circuit. The friend wants to just keep it plugged into that non-gfci circuit. I'm not 100% confident that the water cooler is the issue since there was definitely a resistance between hot and neutral and then the problem just disappeared....but if it is, would it be safe to plug into a nongfci circuit if it's causing a gfci circuit to trip? It's holding on the circuit but is it safe?

Thanks for the help!

 

[Saturn_Europa]

What do you mean resistance between hot and neutral? Can you please clarify?

When you took your reading is the breaker in the open position? (Never ohm out a hot circuit). Are you reading through the "load" i.e. the water cooler? There should be some continuity there. To test the water cooler, ohm it out to ground.

To test the circuit. Unplug everything. Lock the breaker in the open position or unwire it and then ohm from the ungrounded conductor to the grounding conductor then to the grounded conductor.

 

[GoldDigger]

A resistance between hot and neutral just means that there is a load connected somewhere. If you are sure that you have unplugged or turned off all loads, including the hidden ones, then a resistance from hot to neutral with the breaker open probably indicates a wiring fault.

An appliance or device with only a two wire cord can still have leakage to ground, depending on what it is touching. And a "real" leakage of 5ma might not trip a GFCI unless something else is leaking 1 or 2 ma.

 

[arfrcchic]

What do you mean resistance between hot and neutral? Can you please clarify?

When you took your reading is the breaker in the open position? (Never ohm out a hot circuit). Are you reading through the "load" i.e. the water cooler? There should be some continuity there. To test the water cooler, ohm it out to ground.

To test the circuit. Unplug everything. Lock the breaker in the open position or unwire it and then ohm from the ungrounded conductor to the grounding conductor then to the grounded conductor.

The circuit was off while trouble shooting but I turned it on each time to verify whether the resistance reading cleared or not with each device. I was not reading through a load but now that you mention it I was reading through the outlet. Nothing was plugged in so no true "load" but I would have been reading through the next load side receptacle. I know from previous troubleshooting that that can give you a resistance reading (which has always confused me because why would the hot and neutral terminals have any contact?).

 

[GoldDigger]

The circuit was off while trouble shooting but I turned it on each time to verify whether the resistance reading cleared or not with each device. I was not reading through a load but now that you mention it I was reading through the outlet. Nothing was plugged in so no true "load" but I would have been reading through the next load side receptacle. I know from previous troubleshooting that that can give you a resistance reading (which has always confused me because why would the hot and neutral terminals have any contact?).

Although we may refer to multiple receptacles as "chained" rather than having individual home runs, the simple fact is that they are all wired in parallel.
Measure from hot to neutral at any point in the parallel circuit and you are measuring the resistance of all loads (that are connected and turned on) in parallel.

A load from hot to neutral is normal and will not by itself trip a GFCI.

Experience aside, I would guess that your five year apprenticeship has been weak on electrical theory.

 

[arfrcchic]

So with the gfci open (no power onload side) I don't get any ohm reading on the ungrounded (hot) to ground or grounded (neutral).

I also ckd a resistance of the plug on the water cooler. Got a reading between hot and neutral but to ground on either.

 

[Saturn_Europa]

The circuit was off while trouble shooting but I turned it on each time to verify whether the resistance reading cleared or not with each device. I was not reading through a load but now that you mention it I was reading through the outlet. Nothing was plugged in so no true "load" but I would have been reading through the next load side receptacle. I know from previous troubleshooting that that can give you a resistance reading (which has always confused me because why would the hot and neutral terminals have any contact?).

I'm not following you a 100 % so please forgive me if I misinterpret your statement. All loads must be unplugged from the circuit to test for a fault between hot and neutral. If you do not do this, you will see resistance between the two. This resistance allows current flow and the device to function. You cant really test for a fault on a circuit unless all loads are disconnected and the breaker is open.

 

[GoldDigger]

So with the gfci open (no power onload side) I don't get any ohm reading on the ungrounded (hot) to ground or grounded (neutral).

I also ckd a resistance of the plug on the water cooler. Got a reading between hot and neutral but to ground on either.

The leakage to ground in the water cooler is probably capacitive, which will not show up on a DC ohmmeter.
You could put an AC milliammeter in series with the ground lead of the cooler to directly measure leakage.

 

[arfrcchic]

A resistance between hot and neutral just means that there is a load connected somewhere. If you are sure that you have unplugged or turned off all loads, including the hidden ones, then a resistance from hot to neutral with the breaker open probably indicates a wiring fault.

An appliance or device with only a two wire cord can still have leakage to ground, depending on what it is touching. And a "real" leakage of 5ma might not trip a GFCI unless something else is leaking 1 or 2 ma.

So the gfci circuit is holding with all two wire appliances. It's only the water cooler, which has a ground plug, that trips it....now anyway. But while I was troubleshooting I got a resistance reading between hot and neutral with no load. However I did have the next load side receptacle still wired down the line as I was troubleshooting....which could have been the resistance reading I was getting. The water cooler has an ohm reading between hot and cold. That shouldn't be right?

 

[Saturn_Europa]

So with the gfci open (no power onload side) I don't get any ohm reading on the ungrounded (hot) to ground or grounded (neutral).

This is what you would expect to see on a good circuit. Are you using a "megger" or the ohm function on your multimeter? A megger will pick up faults that a multimeter wont see.

Regardless, it sounds like your problem is in the water chiller. I would want to meg that out to ground. How old is it?

 

[Saturn_Europa]

The leakage to ground in the water cooler is probably capacitive, which will not show up on a DC ohmmeter.
You could put an AC milliammeter in series with the ground lead of the cooler to directly measure leakage.

I am unfamiliar with a capacitive fault. Can you please explain?

 

[ceb58]

#2- The water cooler doesn't trip any other non-gfci circuit. The friend wants to just keep it plugged into that non-gfci circuit. I'm not 100% confident that the water cooler is the issue since there was definitely a resistance between hot and neutral and then the problem just disappeared....but if it is, would it be safe to plug into a nongfci circuit if it's causing a gfci circuit to trip? It's holding on the circuit but is it safe?

If nothing else trips the GFCI then it reasons that the cooler is the problem. Appliances with compressors can leak current that are low enough to trip GFCI's but not regular breakers. But once the insulation starts breaking down in the compressor it will gradually get worse and leak more current causing a dangerous situation. Therefor the code 422.52 requiring GFCI protection for drinking fountains.

 

[arfrcchic]

Although we may refer to multiple receptacles as "chained" rather than having individual home runs, the simple fact is that they are all wired in parallel.
Measure from hot to neutral at any point in the parallel circuit and you are measuring the resistance of all loads (that are connected and turned on) in parallel.

A load from hot to neutral is normal and will not by itself trip a GFCI.

Experience aside, I would guess that your five year apprenticeship has been weak on electrical theory.

Are you seriously that insecure that you have to puff your feathers and criticize someone just trying to get a little guidance...

Everything you have said has been obvious information and has not been helpful to my question so I'd thank you for not bothering with anymore "help."

It's pretty sad that someone can't get on here and ask a legitimate question to learn something without being criticized. I'll consider this an isolated incident, and that your just a jerk. If I can't get on hear to legitimately try to learn and figure something out without negativity then what good is this site?

 

[arfrcchic]

I'm not following you a 100 % so please forgive me if I misinterpret your statement. All loads must be unplugged from the circuit to test for a fault between hot and neutral. If you do not do this, you will see resistance between the two. This resistance allows current flow and the device to function. You cant really test for a fault on a circuit unless all loads are disconnected and the breaker is open.

I know this. And I'm sorry if I didn't give enough info before. There are three receptacles on this circuit. That's it. The first is a gfci and then two more load side receptacles. I did not have anything plugged in. There was no load when I was getting the resistance reading.

 

[arfrcchic]

If nothing else trips the GFCI then it reasons that the cooler is the problem. Appliances with compressors can leak current that are low enough to trip GFCI's but not regular breakers. But once the insulation starts breaking down in the compressor it will gradually get worse and leak more current causing a dangerous situation. Therefor the code 422.52 requiring GFCI protection for drinking fountains.

That makes sense. Thank you!

 

[Saturn_Europa]

Are you seriously that insecure that you have to puff your feathers and criticize someone just trying to get a little guidance...

Everything you have said has been obvious information and has not been helpful to my question so I'd thank you for not bothering with anymore "help."

It's pretty sad that someone can't get on here and ask a legitimate question to learn something with being criticized. I'll consider this an isolated incident, and that your just a jerk. If I can't get on hear to legitimately try to learn and figure something out without negativity then what good is this site?

I wouldn't take it so personal. You've got to take the good with the bad. I've been on this forum for a bit now and people tend to be very frank. This is a site for professionals and most expect to see well thought out and researched questions.

 

[arfrcchic]

I wouldn't take it so personal. You've got to take the good with the bad. I've been on this forum for a bit now and people tend to be very frank. This is a site for professionals and most expect to see well thought out and researched questions.

Another dig...the question was more about the device than how a gfci circuit works and the theory behind it. It's hard not to take it personal when someone assumes that a question that was clearly not understood, or maybe wasn't portrayed correctly, is indictative of a person's experience.....or professionalism. Thanks for the help...sorry I asked a question that was beneath this forum.

 

[GoldDigger]

I am unfamiliar with a capacitive fault. Can you please explain?

Any two wires near each other will form a (very small) capacitor. If the insulation is very thin and the wires are close together, like in a motor, thàt capacitor will pass a small but measurable current when you apply an AC voltage to it.
That by itself will usually not trip a GFCI, nor will it get worse with time. But if you add to that some resistive current going through deteriorating insulation you might cross the 5-6 ma threshold of the GFCI. The voltage applied by the ohmmeter in a normal multimeter may not apply enough voltage to cause this insulation breakdown to show up.
For that you need a Megger, which can also measure very high resistances more accurately.
If you had nothing plugged into the receptacles and there were no hard wired loads on the same circuit, it is hard to explain your resistance reading except as the result of damaged wiring or hot wires in a receptacle box touching something. Did you remove the downstream receptacles from the box to inspect them? That might have cleared the problem.

 

[JFletcher]

I'm trouble shooting a gfci circuit for a friend. I followed the wiring around, isolating each receptacle. I got to the last receptacle and it seemed to just go away. It was holding with no load (previously it wouldn't hold at all). When I plugged all the appliances back in, that they had originally plugged in, their water cooler tripped the gfci. The water cooler has a grounded plug but all the other devices do not. It holds with everything else but the water cooler. So I tried a different appliance (steam cleaner) that had a ground plug to see if it's the device or if its the gfci circuit wiring. It held with the cleaner running. It's still holding.

So...two questions:

#1- the fact that originally I had the circuit tripping and I had a resistance reading between hot and neutral...then that just went away by the time I got to the last outlet. Was puzzling but now it's holding. Could it just be a fluke?

#2- The water cooler doesn't trip any other non-gfci circuit. The friend wants to just keep it plugged into that non-gfci circuit. I'm not 100% confident that the water cooler is the issue since there was definitely a resistance between hot and neutral and then the problem just disappeared....but if it is, would it be safe to plug into a nongfci circuit if it's causing a gfci circuit to trip? It's holding on the circuit but is it safe?

Thanks for the help!

1) You may have had a load side fault on the GFCI, like the bare grounding conductor touching the grounded conductor, which fixed itself when you removed the receptacles. Could have been a nick in the wire insulation. What was the exact resistance reading?

2) Test the water cooler on another GFCI receptacle. They do fail over time. If the one is more than 15 years old, Id replace it. They arent that expensive, but if cost is an issue, temporarily wire up a new one off the truck.

If it trips another GFCI circuit/receptacle, it has a ground fault and shouldnt be used.

 

[ptonsparky]

I am unfamiliar with a capacitive fault. Can you please explain?[/QUOTE

Think of how a capacitor is built. Two plates separated by an insulator. Size of the plates and thickness of the insulator determine the value IIRC. Apply AC power and you have current flow.

Now think of the hundreds of feet of motor windings as one plate and the grounded motor case as the other, separated by the varnish on the wire.