GFCI receptacle with hot,neutral reversed

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electricman2

electricman2

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North Carolina
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Retired Electrical Contractor
Just curious, would having hot and neutral reversed on a GFCI receptacle affect its operation? Reason for asking is I had one that would sometimes trip and would not reset. Corrected wiring and now seems OK. It still may be bad but the fact that it was miswired got me thinking.
 
For at least the past decade reverse wired GFCI receptacles have been designed to not power on.
 
Do you know how this is done? I've seen drawings on how the test button is wired in and how it works, but have not caught how a reverse wired device is stopped from coming on.
 
oldsparky52 said:
Do you know how this is done? I've seen drawings on how the test button is wired in and how it works, but have not caught how a reverse wired device is stopped from coming on.
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I've seen and dealt with GFCI's that were reversed (Line on load, load on line) that would not work properly.
 
electricman2 said:
Just curious, would having hot and neutral reversed on a GFCI receptacle affect its operation? Reason for asking is I had one that would sometimes trip and would not reset. Corrected wiring and now seems OK. It still may be bad but the fact that it was miswired got me thinking.
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My Opinion: Your question is a lot more complicated than you would think. There have been so many different types of GFCI protected receptacles manufactured over the years that it would be impossible to say what they would do.

I went to a house one time where a home inspector had written up all the GFCI protected receptacles not tripping when he used his plug in tester.I used the test button and they tripped and then I used my plug in tester and they worked so I started to wonder what was going on. I called the guy and he and I had a talk about this to see if we could figure it out. It turned out that I was using an Ideal tester and they tripped and he was using a Sperry tester and they wouldn't trip. I even went to they local HD and bought a new Sperry tester and it would not cause the receptacles to trip.

I'm pretty sure that the difference was a different resistance to ground used by the different testers. I suggested he buy a different tester or to rely on the test button.

Back to the original question: I have actually seen GFCI receptacles that had revered line and load that would work but naturally the test button wouldn't function properly and there was no feed through to down steam receptacles.

When I have any kind of a problem with a GFCI receptacle I just replace it with a new one of good quality ( at least a good brand name).

Edit: When installing even a new GFCI receptacle use the test button a couple of times because I have seen a couple that were not working properly right out of the box.
 
On a two wire (No EGC) circuit, how does the GFCI know which is hot and which is neutral? I'll bet they will work fine with hot and neutral reversed on a two wire circuit.

The same GFCI on a three wire circuit may not work with the hot and neutral reversed. Which makes total sense to me.
 
K8MHZ said:
On a two wire (No EGC) circuit, how does the GFCI know which is hot and which is neutral? I'll bet they will work fine with hot and neutral reversed on a two wire circuit.

The same GFCI on a three wire circuit may not work with the hot and neutral reversed. Which makes total sense to me.
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The GFCI does not need to "know" which wire is grounded, only that there is a difference in current between the two wires. The test button also does not use the EGC like a plug-in tester does, so again polarity should not matter. A GFCI that will not reset with reversed polarity must be using the EGC as a reference.
 
Some difference or asymmetry in the GFCI circuitry between the hot and neutral sides is necessary because of the need to detect and trip on neutral-to-ground faults as specified in UL 943. For example the neutral is the ground reference for the IC and peripheral circuitry of the GFCI implementation shown in Fig. 3 of the following document for the RV4141A integrated circuit. The hot is not connected except through the resistor used for emulating a ground fault using the test button.

https://www.onsemi.com/pub/Collateral/RV4141A-D.pdf#page=7
 
LarryFine said:
The GFCI does not need to "know" which wire is grounded, only that there is a difference in current between the two wires. The test button also does not use the EGC like a plug-in tester does, so again polarity should not matter. A GFCI that will not reset with reversed polarity must be using the EGC as a reference.
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My observation primarily with P&S GFCI's is hot/neutral reversal will not impact operation, and shouldn't if they are just using a CT to detect current imbalance to initiate a trip.

Line/load reversal however they will not reset once they have tripped unless they are receiving voltage input on the line terminals. If you have it in "reset state" and then reverse line and load wires, it will continue to operate and will even still trip, but will not reset because there is no voltage on the line terminals. If it is not powered and you press the reset button it will seem to latch, but will unlatch once power is applied. They must somehow be designed that you must have power on line terminals during the reset operation or it won't actually "set".

New ones out of the box almost always trip even if the reset button is in the "set position" I believe they likely are made or finished with any testing in a tripped condition and then the reset button may very well be pressed but with no power on the line terminals - and it is shipped in this condition - hence they almost always trip the first time you energize them.
 
:thumbsup:

The only effect of a hot/neutral reversal would be that it would try to detect a grounded hot instead of a grounded neutral. This will not result in a false trip but will render that extra feature inoperative. And that feature would not work on a ground free branch circuit in any case.
 
GoldDigger said:
:thumbsup:

The only effect of a hot/neutral reversal would be that it would try to detect a grounded hot instead of a grounded neutral. This will not result in a false trip but will render that extra feature inoperative. And that feature would not work on a ground free branch circuit in any case.
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I could see it not working on an ungrounded system but still working on grounded system with a branch circuit that doesn't include an EGC.

Be sort of rare to have ungrounded 120 volts. One case that would be somewhat normal is a portable generator that has no neutral to frame bond but if you are properly connecting it to any premises wiring the premises wiring should still have a ground connection.
 
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