GFCI Receptacle with GFCI pigtail

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iwire said:
If we are going to continue this discussion we should all be talking the same language.

Ungrounded conductor (AKA the hot, the black etc.)

Grounded conductor (AKA the neutral, the white etc.)

Grounding conductor (AKA the ground, the green, bare etc.


"PE" has no meaning in the NEC
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What the heck is a PE??
 
With the extra coils, they trip as soon as power is applied.
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The same think will happen without the extra coils as long as there is current flowing on the line side grounded conductor, assuming a grounded to grounding fault on the load side of the GFCI. If there is no current flowing on the line side grounded conductor, then it won't trip on a grounded to grounding fault without the extra coils.
Don
 
don_resqcapt19 said:
The same think will happen without the extra coils as long as there is current flowing on the line side grounded conductor, assuming a grounded to grounding fault on the load side of the GFCI. If there is no current flowing on the line side grounded conductor, then it won't trip on a grounded to grounding fault without the extra coils.
Don
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Thank you! That's what I was trying to say in my long-winded post (#35). You said it better than I. e/m.
 
wptski said:
Just to double check, my Leviton, P&S and Cooper all work the same way, maybe not required but they do!
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That may be but I know of at least one major brand of GFCI breaker does not therefore you should not infer that all GFCI devices work in this manner.

This sounds like a nice feature to have, so I wonder why aren't the manufacturers talking this up in their marketing literature?
 
It was strange to me that manufacturers to not highlight the N-PE (or EGC)
checking feature. When I went looking for a unit to purchase for test I did not see it advertized on the packages. I bought a Leviton SmartlockPro because it stated that it met the 2006 UL Requirements and looked to be more advanced.

The first time I tested it it did not appear to trip (I was testing incorrectly).
I called Leviton technical support and when I explained that I was wanting a unit that performed the neutral-ground fault detection, the tech told me it did not exist. After he talked with an engineer the engineer told him that feature existed in all GFCIs.

I think the second core was added at some point in history , probably to meet changing UL standards (perhaps in 2006)?

I then went back and tested the 7599-I unit I bought once again using progressively smaller resistors (connected from load Neutral-EGC) and at about 30 ohms the unit would trip with no load on the hot lead.
I thought it was a pretty nice feature.
 
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jim dungar said:
That may be but I know of at least one major brand of GFCI breaker does not therefore you should not infer that all GFCI devices work in this manner.

This sounds like a nice feature to have, so I wonder why aren't the manufacturers talking this up in their marketing literature?
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I did say "newer" but wonder when this added change started to take place? That's because nobody told marketing yet!
 
ELA said:
I then went back and tested the 7599-I unit I bought once again using progressively smaller resistors (connected from load Neutral-EGC) and at about 30 ohms the unit would trip with no load on the hot lead.
I thought it was a pretty nice feature.
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This a bit confusing, to me, anyway! The GFCI is checking to make sure that N-G aren't shorted at the receptacle but they are at the service enterance. If you pull the power and measured the resistance from N-G, it's going to be far less than 30 ohms as that's lots of copper.

I've actually measured this on a few circuits in my home and the most I read was 1 ohm or so.

BTW: Leviton GFCIs that I've checked have a much long trip time than P&S but not the Cooper which was a bit longer.
 
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wptski said:
This a bit confusing, to me, anyway! The GFCI is checking to make sure that N-G aren't shorted at the receptacle but they are at the service enterance. If you pull the power and measured the resistance from N-G, it's going to be far less than 30 ohms as that's lots of copper.

I've actually measured this on a few circuits in my home and the most I read was 1 ohm or so.

BTW: Leviton GFCIs that I've checked have a much long trip time than P&S and Cooper.
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True that the copper resistance is fairly small, specially for larger cross sections and short runs. But even at 1 ohm, if your N is carrying say 3 amps, that is a three volt drop on the length of the N, based on the ohm's law. Now imaging this end of the N (the load end) touching the ground (which is at zero volts). Some of the three amps that was going through the N, is now going to go through the ground connections. The GFCI will sense this drop in the current in the N (remember that the H is still carrying the full 3 amps), and will trip. For the no load scenario, you will need that second torroid for it to trip, else the GFCI cannot detect a N-G short.
 
Energy-Miser said:
True that the copper resistance is fairly small, specially for larger cross sections and short runs. But even at 1 ohm, if your N is carrying say 3 amps, that is a three volt drop on the length of the N, based on the ohm's law. Now imaging this end of the N (the load end) touching the ground (which is at zero volts). Some of the three amps that was going through the N, is now going to go through the ground connections. The GFCI will sense this drop in the current in the N (remember that the H is still carrying the full 3 amps), and will trip. For the no load scenario, you will need that second torroid for it to trip, else the GFCI cannot detect a N-G short.
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I understand if it has a load but ELA test was with no load which confuses me.

I have a Ideal Suretest and use of a Fluke 1653 loop tester, UK styled tester. The Suretest will trip a GFCI during G impedance test but will still register a value before it trips. It and the 1653 which doesn't trip a GFCI both read much higher through a GFCI. What this means, I don't know!
 
wptski said:
I understand if it has a load but ELA test was with no load which confuses me.

I have a Ideal Suretest and use of a Fluke 1653 loop tester, UK styled tester. The Suretest will trip a GFCI during G impedance test but will still register a value before it trips. It and the 1653 which doesn't trip a GFCI both read much higher through a GFCI. What this means, I don't know!
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hm... not sure. Have not used any of those, just the garden variety outlet tester, with a button for the GFI test. e/m
 
These GFCIs, with the second core, are designed in such a way that they will only sense a short on the (load side neutral to PE (Protective Earth) or EGC ).

The cores are arranged in a way that will not sense, or trip, on the bond at the service directly. Yet as explained below the service bond is essential for this to work.

When I first tested the GFCI I shorted from the line side neutral to PE and the breaker does not trip. When shorting from the load side neutral to PE (at less than 30 ohms) it does trip. This is with no load on the hot lead.

As the linked site explained:

"If there is a N-G short downstream, a current will flow through the N wire, to the G wire via the short, and back to the N wire via the normal connection at the service panel. Since there will be NO similar current in the H wire, this represents a current unbalance and will trip the GFCI in the same manner as the usual H-G short."
 
ELA:

I understand that but it just seems like 30 ohms is pretty high to me but it may make sense if we knew what was signal level injected by the second coil.
 
What first interested me in investigating this was how they could accomplish this neutral -ground checking without introducing a new hazard. If the voltage on the load conductors was high enough that would be an issue.

I measured the voltage on the neutral to ground and it was only approx. 0.2 volts. That is consistent with (.006)Amps x (30) ohms.

Heres how I interpret its operation:
This second core is basically an open seconday transformer. Lots of turns on the primary and only one turn on each secondary (one for neutral and one for hot).

Until the load side earth-ground connection is made (completes the secondary circuit) there is no path for current to flow.
I believe that 30 ohms causes the 6ma to flow and thus the trip time is probably slower at 30 ohms. One ohm would cause much more current to flow and the device would trip faster.
 
ELA:

Using a Leviton GFCI. I used a Fluke 87V, 400ma input in Peak or Fast min/max mode which capture events as short as 250us. The min/max which captures events as short as 100ms wouldn't catch the events. A week or so ago I blew the 400ma input fuse due to these quick events on a GFCI while using the Ideal Suretest!:mad:

Connected between N-G.

Resistor/Current
none/285ma
10 ohm/49ma
25 ohm/22ma

Not even sure if this helps or just adds more confusion? Our testings methods are different for sure but there a peak, sort-of like a inrush going on here and I don't know if it's better to look at a peak or average. Later this week I "hope" to have a way to capture and post a scope waveform of the complete event.
 
wptski,


I am not sure I followed your post and how you tested? In particular did not understand.

"none/285 ma "

I do not have access to any of the GFCI testers.

My test was very crude. I took a 30 ohm resistor and connected it from the load neutral to the EGC and noted the trip of the GFCI. I did not attemp to measure the current.

It would be interesting to capture an event on a scope.
 
ELA:

The DMM was connected between neutral and the ground wiper on the receptacle. The first value is with no resistor at all. Also noticed that if you didn't wait enough between tests, the current increases. Using no resistor, the current went 285ma>800ma>1.3A.
 
wptski said:
ELA:

The DMM was connected between neutral and the ground wiper on the receptacle. The first value is with no resistor at all. Also noticed that if you didn't wait enough between tests, the current increases. Using no resistor, the current went 285ma>800ma>1.3A.
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I am not familiar with the meters you were using. It sounds like you are putting a resistor in series with the ammeter section of the meter? Such that no resistor is actually zero ohms? Ok I think I am on track. That makes sense to me now.

so 0.2v / 0.285A = 0.7 ohms (resistance of meter and leads)
and 0.2V / 30 ohms = 0.006A ( the max reistance that will trip the GFCI)

as far as the peak or inrush... don' know - the average is good enough for me.
 
ELA:

I tried to find the value of the shunt resistor used in the DMM but its specs don't list it! The "general" value most often used is .001ohm. I do have a purchased .001 ohm shunt resistor mounted in a block-like unit. I may try to insert that but the voltage drop would be pretty low to measure with a DMM.





edited per posters request to remove waveform
 
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