Thread: Double GFCI's still not right

Double GFCI's in the bathroom, should be double protection, right? Except the right receptacle stays hot after it is tripped.
And the left one can't trip because the right one snaps off first every time.

I guess you have already figured out they were not installed correctly.

The right one has line and load wired backwards.

The left one is wired as feed-through off the right one instead of wired as by-pass off the right one.

Yeppers, someone did not know what they were doing.

Sometimes I wish I could do a pre-inspection tour through the house, and fix this small stuff so I wouldn't have to write them all up, and then explain what I wrote and why it is wrong.
PS the other bathroom has no GFCI.

Originally Posted by John Kogel

PS the other bathroom has no GFCI.

And was not protected by one of the other GFCIs?

The receptacle is not required to 'be' a GFCI receptacle, only that it 'be' GFCI protected.

Originally Posted by Jerry Peck

And was not protected by one of the other GFCIs?

The receptacle is not required to 'be' a GFCI receptacle, only that it 'be' GFCI protected.

No, the downstairs receptacle is not protected by either of those 2 upstairs. Incredible as it may seem.
Older house with bathroom outlets on different lighting circuits.

I also find more and more receptacles in bathrooms being downstream from the GF located in the garage.

Clearly not right. As to why? Since I have never wired one incorrectly (as in backwards...lineside to load and vice versa) I am not sure how it would behave; but obviously it would not work correctly. I think what Jerry said is correct.

Seems like I find problems with GFCI's on just about every home. And that is not counting homes that do not have GFCI protection because of when they were built. All kinds of weird abnormalities.
These abnormalities seem to depend on the year that the home was built, or when upgrades to GFCI's were done [and by whom].

And thank you Jerry Peck for the GFCI and AFCI documents [reference sheets] that you made up showing where and in what year, according to code they were to be used or required. I use these as attachments and make reference to them on many of my reports!
I always attach these to the reports of older homes and recommend they be installed [by an electrician]

Yes ! Thanks Jerry, I use those documents as well

Jim

I have no solid thought to bring truth to this but an electrician's told me that more than one GFI on a circuit may cause them to oppose each other and can cause dead repository.


Thanks
epackpolymers.com

Originally Posted by jakson

I have no solid thought to bring truth to this but an electrician's told me that more than one GFI on a circuit may cause them to oppose each other and can cause dead repository.

Not quite sure of some of your terms, but from what I think you are saying (that one GFCI will interfere with another GFCI and cause one or the other to trip off) that electrician would be incorrect.

However, if GFCI #2 is wired as fed-through GFCI #1, when GFCI #2 has something plugged into it which may cause its GFCI to trip, GFCI #1 may trip instead or GFCI #2 tripping, may trip at the same time as GFCI #2, or may not trip at all.

That is not caused by one GFCI interfering with the other, that is cause by whichever GFCI is the most sensitive will trip first. If both are exactly the same in tripping sensitivity then both will trip at the same time. If one trips at 5.0 ma and one trips at 5.1 ma, the GFCI which trips at 5.0 ma will trip first, whether that is GFCI #1 or GFCI #2.

Where can I find the GFCI and AFCI notes prepared by Jerry?

Originally Posted by michael Rodney

Where can I find the GFCI and AFCI notes prepared by Jerry?

Cool Looky... what I found on Jerry's Page, go to this link...you can thank me later

Construction and Litigation Consultants

Originally Posted by Jerry Peck

Not quite sure of some of your terms, but from what I think you are saying (that one GFCI will interfere with another GFCI and cause one or the other to trip off) that electrician would be incorrect.

However, if GFCI #2 is wired as fed-through GFCI #1, when GFCI #2 has something plugged into it which may cause its GFCI to trip, GFCI #1 may trip instead or GFCI #2 tripping, may trip at the same time as GFCI #2, or may not trip at all.

That is not caused by one GFCI interfering with the other, that is cause by whichever GFCI is the most sensitive will trip first. If both are exactly the same in tripping sensitivity then both will trip at the same time. If one trips at 5.0 ma and one trips at 5.1 ma, the GFCI which trips at 5.0 ma will trip first, whether that is GFCI #1 or GFCI #2.

One way to really screw up the workings of 2 GFCI's would be to wire them in parallel with a receptacle downstream. Then a 5 milliamp fault at the downstream outlet would be divided and neither device would trip until the amperage of the fault reached about 10 mA.
We would not likely ever encounter a house circuit wired that way, but it is possible when Billy Bob puts 2 GFCI's are in the same box.

Originally Posted by John Kogel

One way to really screw up the workings of 2 GFCI's would be to wire them in parallel with a receptacle downstream. Then a 5 milliamp fault at the downstream outlet would be divided and neither device would trip until the amperage of the fault reached about 10 mA.
...

Sorry, but I don't think that's how it works.
Can you explain?

Originally Posted by John Kogel

One way to really screw up the workings of 2 GFCI's would be to wire them in parallel with a receptacle downstream. Then a 5 milliamp fault at the downstream outlet would be divided and neither device would trip until the amperage of the fault reached about 10 mA.
We would not likely ever encounter a house circuit wired that way, but it is possible when Billy Bob puts 2 GFCI's are in the same box.

Nope.

Whatever was the cause of the ground fault and was plugged into one of the GFCIs would trip the GFCI it was plugged into.

Originally Posted by John Kogel

One way to really screw up the workings of 2 GFCI's would be to wire them in parallel with a receptacle downstream. Then a 5 milliamp fault at the downstream outlet would be divided and neither device would trip until the amperage of the fault reached about 10 mA.
We would not likely ever encounter a house circuit wired that way, but it is possible when Billy Bob puts 2 GFCI's are in the same box.

Originally Posted by Rick Cantrell

Sorry, but I don't think that's how it works.
Can you explain?

Originally Posted by Jerry Peck

Nope.

Whatever was the cause of the ground fault and was plugged into one of the GFCIs would trip the GFCI it was plugged into.

Plug the faulty appliance into a 3rd receptacle downstream from 2 GFCI's wired in parallel. The fault current is divided in half through each GFCI. That is the only way I can think of 2 units interfering with each other.

Originally Posted by John Kogel

Plug the faulty appliance into a 3rd receptacle downstream from 2 GFCI's wired in parallel. The fault current is divided in half through each GFCI. That is the only way I can think of 2 units interfering with each other.

Nope.

Doesn't work that way.

The GFCI receptacles are already in parallel - that is how circuits are wired.

If they were wired in series than nothing down stream of the first would work until you stuck a paperclip into both slots of the first GFCI to act like turning a switch on.

Anything downstream of the first GFCI wired in feed-through has the first GFCI reading the current through both the hot and the neutral.

Anything downstream of the second GFCI wired in feed-through from the first GFCI and feed-through to downstream has both the first GFCI AND the second GFCI BOTH reading the full current on the full current from downstream.

All the GFCI is doing is reading the hot and neutral current at the same time, when there is an imbalance between the two then there is a ground fault somewhere down stream, when that imbalance is between 4 ma and 6 ma the GFCI is supposed to trip off.

Picture this, JP. They would not be daisy-chained in the normal fashion because this is someone doing it wrong.
The black goes to both GFCI's, jumpered together.
The white neutrals, the same. Now jumper the load terminals together.
Now put another receptacle on a pigtail from those paired leads from the two load terminals. Any current to that receptacle goes through both GFCI's.
Ohm's law, the current will be split.

John,

If it is wired exactly as you describe then the current would split just as you say. However, in the real world homes or circuits are not wired like that.

The reality is, both GFCI's can be tied together on the hot or line side. However, the loads sides are never tied together. They would in fact go to different receptacles down stream. So Jerry is right. Only one GFCI would see the imbalance, and trip.

Thanks,

Originally Posted by John Kogel

Picture this, JP. They would not be daisy-chained in the normal fashion because this is someone doing it wrong.
The black goes to both GFCI's, jumpered together.

That is how they are usually wired when wired in by-pass, not feed-through.

The white neutrals, the same.

That is the same as the above, the normal way when wired by-pass.

Now jumper the load terminals together.

That is where you are losing me - jumper the hot load to hot load and neutral load to neutral load?

Now put another receptacle on a pigtail from those paired leads from the two load terminals.

How could you do that in an installation where the GFCI receptacles were not side-by-side but were separate from one another?

How could you do that with the GFCI receptacles were side-by-side as shown? How would you get your third receptacle there?

You are talking about more than just "someone doing it wrong", you are talking about a strange setup almost like someone was doing it on purpose - that is not "doing it wrong" that is "experimenting to see what happens".

Any current to that receptacle goes through both GFCI's.
Ohm's law, the current will be split.

If you could manage to do it as you describe, which I am not following the 'how it would accidentally be done that way' part, then, yes, half of the current on the hot would be through each GFCI, as would half of the current on the neutral would be through each GFCI, and thus the ground fault current would indicate as being half in each GFCI receptacle too. But I'm trying to figure out the initial layout which would allow for such a wiring of them ...

Thanks, Jerry. The electrician says that 2 GFCI's would interfere with each other. I says yes, but only if you wired them in that way, not gonna happen.

(I think his meaning may have been daisy-chained GFCI's can be a PITA, having to restore power to one before you can reset the other, yep we see that all the time. But they work just fine that way and if one's faulty, the other one is there to protect you.)