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Thread: GFCIs
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06-19-2018, 05:44 AM #1
GFCIs
Hey folks,
My question is concerning GFCIs in pre-1970s ungrounded homes.
Does putting a GFCI outlet in that still tests ungrounded, provide any additional protection than a normal 2 prong ungrounded outlet?
Thanks
Rick
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06-19-2018, 05:45 AM #2
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06-19-2018, 07:35 AM #3
Re: GFCIs
Rick,
The short answer is "Yes, GFCI add a level of safety to receptacle outlets on ungrounded circuits."
The long answer is that if you to use a GFCI tester on an ungrounded GFCI - the tester will not trip the GFCI as the tester requires a ground to create the test fault current to and there is no ground; however, the circuit within the GFCI does not require a ground to trip the GFCI as the person (or item) creating the ground path for the ground fault serves as that grounding conductor - additionally, the GFCI test button itself does not need a ground to trip the GFCI as the test circuit itself creates a fault path within the GFCI test circuit and trips the GFCI.
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06-19-2018, 06:56 PM #4
Re: GFCIs
Robert Young's Montreal Home Inspection Services Inc.
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06-20-2018, 04:03 AM #5
Re: GFCIs
Thanks Jerry, I appreciate the exact and quick answer to my question.
I believed it did and I've not written it up as an issue on inspections. but sometimes your mind wanders.
Thanks again
Rick
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11-13-2019, 04:47 PM #6
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11-13-2019, 05:37 PM #7
Re: GFCIs
Yes.
Test the downstream receptacle outlets (test all receptacle outlets in the room) first, use the GFCI receptacles "test" button to trip the GFCI, then plug your tester into each of the other receptacles outlets again - if any of those other receptacles are still 'on', then they are not GFCI protected ... by that GFCI receptacle (a GFCI receptacle may protect some receptacle outlets in on room, and some in another room, which means testing can become repetitive as circuits in those older homes (ungrounded circuits indicates an older home) often supplied more than one room, or parts of more than one room.
The second test can be done quicker with a voltage sniffer - hold the voltage sniffer near each opening on the receptacle (hot, neutral, and ground) and if it goes off, there is still power that receptacle.
Or ... buy a bunch of cheap night lights, plug them into the different receptacle outlets so you can see the night lights are 'on', push the GFCI 'test' button, and any night light which did not go 'off' still has power - this saves some walking around as you can use your tester to test for polarity at a receptacle outlet, plug in a night light, then go to the next receptacle ... the only retracing of your path is to collect the night lights. Works good for vacant rooms, but furnishings can get in your line of sight to the night light.
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11-13-2019, 05:54 PM #8
Re: GFCIs
Basically, I did your first recommendation. Trip the GFCI at the top of the circuit and see if the receptacles downstream are dead. I was wondering if there is a device to trip the controlling GFCI from one of the downstream ungrounded receptacles to prove that the GFCI will definitely respond to a ground-fault at a downstream receptacle.
If you choose not to decide, you still have made a choice.
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11-13-2019, 06:58 PM #9
Re: GFCIs
That's what the 'test button on the GFCI receptacle does.
During a ground-fault condition (also under a no ground-fault condition), full amperage of whatever is plugged in goes through the ungrounded (hot) conductor from the circuit conductor upstream feeding the GFCI device receptacle, through the GFCI test circuit in the GFCI, and out through the downstream ungrounded conductor to the other receptacles.
During a no ground-fault condition, the same exact current goes through the grounded conductor at the other receptacle being used, back to the GFCI device receptacle and the GFCI test circuit, then out the GFCI device receptacle and upstream through the ungrounded conductor.
The GFCI device receptacle test circuit creates a 5 ma bypass around the GFCI test circuit when the 'test' button is pushed, that now creates a 5 ma imbalance between the grounded conductor and ungrounded conductor through the GFCI test circuit coil, that 5 ma imbalance creates a current in the coil which causes an internal switch to open, shutting down the GFCI and everything downstream of it.
During a ground-fault, that 5 ma imbalance is created by and through the person (appliance, etc) which is creating the ground-fault. That imbalance between the grounded conductor and ungrounded conductor is also through the GFCI test circuit coil in the GFCI device receptacle.
Just like the 5 ma imbalance created by the GFCI test circuit, that actual 5 ma ground-fault trips the internal switch and shuts off the GFCI device receptacle and everything downstream of it.
Thus the GFCI test button on the GFCI receptacle is the same as if you could actually create a ground fault at a downstream receptacle outlet.
The above said, though (which should be enough to answer your question), I recall that, at some point in time, I saw an advertisement for a device which could create a false 5 ma ground-fault downstream of the GFCI device receptacle ... which is, I think, your specific question.
I haven't seen or heard anything about that tester in quite some time - likely because there was no real market for it (there is no need for it).
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11-13-2019, 07:09 PM #10
Re: GFCIs
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11-14-2019, 07:36 AM #11
Re: GFCIs
Thanks. Great answer by the way.
So the conclusion that I'll make is; No test device is needed to confirm that the downstream receptacles from a GFCI are wired correctly, because IF the test button on the GFCI receptacle near the top of the circuit, kills the receptacles downstream, then the circuit is wired correctly.
As a side note on this inspection, I found one ungrounded, unprotected receptacle in the attic, and several receptacles missing the required labels (most were appropriately labeled). This was one of the better rehabs that I've seen even if not perfect.
If you choose not to decide, you still have made a choice.
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11-14-2019, 07:55 AM #12
Re: GFCIs
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11-14-2019, 10:59 AM #13
Re: GFCIs
Correct.
The GFCI test device I saw for testing ungrounded receptacle outlets was a box with a cord and grounding type plug coming out so it so it could be plugged into a receptacle, then a 15-25 foot ground wire coming out of it so that ground could be attached to a grounded point.
As I recall there was an optional 25 foot ground wire too. Okie dokie, that would let you go find a ground within 50 feet ... yeah, right ... and they you have that 50 foot ground wire to roll back up.
The box had a built-in GFCI test button built into it.
Two things wrong with the device: a) it was not needed, the GFCI test button on the protecting GFCI receptacle device did the same test; b) dealing with finding a ground on an ungrounded wired house - water pipe someplace? (what if the water pipe was not bonded to ground, failed the test? what if the ground clamp didn't make a good connection to the ground, failed the test?).
Lon,
If you want to try testing ungrounded receptacles for GFCI protection, here is a simple test device you can make (but has the same drawbacks as described above):
Get a plastic box, put a grounded receptacle outlet in it, connect a grounded cord and plug to it so you can plug it in, connect a ground wire coming out of it to be connected to a ground ... and there is your test device.
The GFCI test is performed how? By plugging in your SureTest (or any other GFCI tester) into the receptacle outlet.
Plug the test device into a receptacle outlet to be tested, plug the SureTest into the device's receptacle outlet, connect the ground wire to a ground (verify that it is actually grounded), then use the SureTest GFCI test function to test the GFCI tripping (the advantage of the SureTest is that it tells you at what ma the GFCI being tested trips at, and - as I recall - the ms it took to trip).
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11-14-2019, 11:21 AM #14
Re: GFCIs
I like it.
Now that we have discussed this at length and for newbies reading all this, I think for home inspectors, testing the controlling GFCI and determining that ungrounded receptacles are protected is sufficient. I did use a circuit tester, but as expected, it didn't "see" anything more significant than the 3-light tester.IMG_8091.JPG
If you choose not to decide, you still have made a choice.
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11-14-2019, 12:11 PM #15
Re: GFCIs
While we are on GFCIs ... but a slight thread drift is below ...
Mike Holt will be updating my GFCI and AFCI pages from the 2014 pages I stopped at.
He will likely do the 2017 update sometime after the first of next year, I suspect that his update will include 2017 and 2020 at the same time as there is no need for a separate 2017 page, only to be replaced with a 2020 page.
Currently, Mike is working on his 2020 Changes to the NEC videos and other things he puts out, so I would not expect the updates 'immediately after' the beginning of next year (I don't know what his schedule is, but Mike has agreed to update the pages - a big Thank You to Mike Holt for continuing those pages).
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