Testing an ungrounded GFCI

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alfal

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Hi All -

I am replacing an outlet that is only fed by ungrounded wire. As read all over this site and the web, I am attempting to replace it with a GFCI outlet. The test button on the GFCI works correctly, but I have a tester that is supposed to simulate a fault and trip the GFCI, but it is not doing so. Is this to be expected without the ground connected? Is it possible my tester is not simulating the fault properly? I have tried this with another GFCI outlet to verify the outlet is not at fault.

Thanks -

Al
 
The test button is the only test that needs to be done. Your tester will not trip a GFCI connected to a two wire circuit without bringing an outside EGC or alternate fault current path in to the picture, this does not indicate an unsafe situation.

Roger
 
Roger,

Thanks for the quick reply. So, I am assuming these cheap testers use the ground as the alternate path to trip the GFCI?

Al
 
Al, cheap or expensive testers make no difference, without the third path for current to flow (split in a parallel path if you will) the GFCI will see zero current through it's sensor and will not trip. Even though an external tester will not trip a GFCI due to this fact, a current imbalance in a real world fault / situation will.

Check out this short article on the subject.

http://www.codecheck.com/gfci_testing.htm

Roger
 
If it gives you some peace of mind, you can use a wiggy to trip the GFCI by another path (metallic water piping, dirt, whatever).

69115.jpg


It will not prove that the GFCI will trip at the required current (4mA - 6mA), but it is another means outside the integral test button to use.
 
Ok I am slightly confused, please forgive my ignorance..

Are you telling me you can install a GFCI receptacle on a 2 wire circuit, where there is no ground available?? It will function properly except when testing it with a plug in tester?

Roger
 
Yes and yes

Roger
 
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RAM460 said:
Are you telling me you can install a GFCI receptacle on a 2 wire circuit, where there is no ground available?? It will function properly except when testing it with a plug in tester?
Click to expand...
This is probably one of the best reasons to a three prong to two prong cheater available in the tool kit. Plug the GFCI testor into the cheater. Plug the cheater into the GFCI. Clip a wire on the cheater EGC tab and run the other end to a known ground. . .then the plugin GFCI tester will accurately test the GFCI sensor circuit.
 
RAM460 said:
Are you telling me you can install a GFCI receptacle on a 2 wire circuit, where there is no ground available?? It will function properly except when testing it with a plug in tester?
Click to expand...

Correctamundo. Remember, to trip a GFCI, some current has to flow through the sensor ring, on the hot wire, that returns to the neutral/ground/earth without going through the ring.

The reason a GFCI's built-in test button works is because the test circuit has access to the neutral before it passes through the ring; the plug-in tester does not, and has to use the EGC.
 
Okay folks, gotta ask a stupid question. Do none of you guys connect a pigtail from the ground screw to the grounded conductor on a two wire GFCI? I do this so that the ground prong on the appliance is connected to ground through the neutral. It is my opinion that if you connect a GFCI to a grounded (or neutral) conductor, you will enable the grounding conductor for the appliance to actually be grounded. Also, should anything go wrong with the appliance you will be just as protected with this wiring arrangement as you would be with no ground connection at all. AND your tester would work!!!!!
 
Johnmcca
Thanks for the heads up. Now I gotta go disconnect 'em all. Still think from an operational standpoint, it would be better to bond at this location. But a rule is a rule. This forum keeps me on my toes! That's why I spend so much time reading and participating.
Thanks again!
 
Hey Ram... I've thought about my answer. It is sorta right but not fully. You don't really have a ground so it isn't really a ground neutral bond. I don't know what code # covers this, but IMO it still isn't right. I'm not really a residential electrician so I don't play with GFCIs too often. I know that the ground isn't needed so I just mark the outlets with the sticker that there is no grounding conductor.
 
alfal said:
Hi All -
Click to expand...
alfal said:

I am replacing an outlet that is only fed by ungrounded wire. As read all over this site and the web, I am attempting to replace it with a GFCI outlet. The test button on the GFCI works correctly, but I have a tester that is supposed to simulate a fault and trip the GFCI, but it is not doing so. Is this to be expected without the ground connected? Is it possible my tester is not simulating the fault properly? I have tried this with another GFCI outlet to verify the outlet is not at fault.

Thanks -

Al
Click to expand...


Al, I have a 25 question test that I give a GFCI or an Arc-Fault device for testing. One is approved as much as the other when using those testing devices. Do as the manufacture of the device advises in their instructions and use the test button on the device and nothing else is needed.

Johnmcca said:
Hey Ram... I've thought about my answer. It is sorta right but not fully. You don't really have a ground so it isn't really a ground neutral bond. I don't know what code # covers this, but IMO it still isn't right. I'm not really a residential electrician so I don't play with GFCIs too often. I know that the ground isn't needed so I just mark the outlets with the sticker that there is no grounding conductor.
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250.142 Use of Grounded Circuit Conductor for Grounding Equipment.
(B) Load-Side Equipment. Except as permitted in 250.30(A)(1) and 250.32(B), a grounded circuit conductor shall not be used for grounding non?current-carrying metal parts of equipment on the load side of the service disconnecting means or on the load side of a separately derived system disconnecting means or the overcurrent devices for a separately derived system not having a main disconnecting means.
Exception No. 1: The frames of ranges, wall-mounted ovens, counter-mounted cooking units, and clothes dryers under the conditions permitted for existing installations by 250.140 shall be permitted to be grounded by a grounded circuit conductor.
Exception No. 2: It shall be permissible to ground meter enclosures by connection to the grounded circuit conductor on the load side of the service disconnect where all of the following conditions apply:
(1) No service ground-fault protection is installed.
(2) All meter socket enclosures are located immediately adjacent to the service disconnecting means.
(3) The size of the grounded circuit conductor is not smaller than the size specified in Table 250.122 for equipment grounding conductors.
Exception No. 3: Direct-current systems shall be permitted to be grounded on the load side of the disconnecting means or overcurrent device in accordance with 250.164.
Exception No. 4: Electrode-type boilers operating at over 600 volts shall be grounded as required in 490.72(E)(1) and 490.74.
 
Ram,

Also, take a look at 406.3(D)(3)(a), (b) & (c) for the language spelling out hooking up a grounding type receptacle and/or a GFCI in a location where the EGC doesn't exist.

From a practical standpoint, if I install a grounding type receptacle with no EGC and I add a jumper from the ground to the neutral on the receptacle and protect it with a GFCI, I set the circuit up for more GFCI nuisance trips, depending on the situation. Take a look again at the graphic that Tom Baker supplied over in post #5 of this thread. . .I'll repost it below:

GFCIOperationWeb.jpg


The graphic shows an "Improper Neutral-to-Case" connection in a switch box.

Imagine that this is the grounding type receptacle with a neutral to ground terminal jumper. I installed the jumper, everything was working when I left. . .and I thought the job was done.

A few weeks later the homeowner installs new wallpaper that has conductive properties. Now the yoke of my receptacle is in contact with the conductive wallpaper.

All that is necessary is for a connection between the wallpaper and. . .say, the heat register, or a water pipe, or some other incidental connection, and the second sensor in the GFCI, the "Grounded Neutral Transformer" primary winding will push enough current through the neutral to ground jumper at the receptacle, out the yoke, through the wallpaper, through the rest of the "ground" conductive path back to the main bonding jumper in the service center (and/or the PoCo transformer grounded conductor) and then return to the GFCI grounded neutral transformer primary winding on the "hot" causing an imbalance that the other transformer reacts to by tripping the GFCI.

I get a call from my customer swearing that the "new" GFCI protected gounded receptacle is "bad" 'cause the GFCI always trips.

Moral of the story: The neutral has to be isolated after the MBJ.
 
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ramdiesel3500 said:
Okay folks, gotta ask a stupid question. Do none of you guys connect a pigtail from the ground screw to the grounded conductor on a two wire GFCI? I do this so that the ground prong on the appliance is connected to ground through the neutral. It is my opinion that if you connect a GFCI to a grounded (or neutral) conductor, you will enable the grounding conductor for the appliance to actually be grounded. Also, should anything go wrong with the appliance you will be just as protected with this wiring arrangement as you would be with no ground connection at all. AND your tester would work!!!!!
Click to expand...
The problem here is that the grounded circuit conductor is just that: a circuit conductor. It should be treated as a hot wire in every sense. Your jumper, which would fool a receptacle tester, actually increases risk of shock.

Suppose a neutral connection upstream of this receptacle developed a resistance. The voltage rise that would occur on the white wire will now also be impressed on the conductive parts of whatever is plugged into this receptacle.

Bottom line: yes, remove the jumpers immediately, please! It's better to properly handle the no-available-EGC properly than to rig it this way that works for testing, but is harmful in real usage situations.
 
ramdiesel3500 said:
Johnmcca
Still think from an operational standpoint, it would be better to bond at this location. But a rule is a rule.
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No it is not 'better'.

The way you have set it up if a neutral is lost between the panel and your jumper the case of any down stream equipment will be at line voltage.

I highly recommend you stop installing these jumpers and remove any you can.
 
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