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GFCI testers - hot to ground question

Posted by grandmum (My Page) on
Sat, Nov 2, 13 at 10:41

I bought a handy GFCI tester the otherday. My son said I wasted my money since he can test the same function with his voltage multitester.

He proceeded to test from hot to ground of a GFCI outlet and it tripped.

Is that the same thing as my GFCI tester or better yet, is that the same thing that happens when someone drops a radio plugged into a GFCI into a bathtub?


Follow-Up Postings:

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RE: GFCI testers - hot to ground question

The questions are slightly ambiguous but the basic answer is "yes".


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RE: GFCI testers - hot to ground question

The GFCI trips on a fault of 30 ma. All you need is a resister of ~4K Ohm to test it which is almost certainly what your testers both do. Of course, in some cases (i.e. that there is no ground) the testers will not trip a properly working GFCI. There's good reason they put a TEST button on the GFCI itself.

The one thing I don't often see these testers doing is testing the ground-neutral fault either.

As to a waste of money, your three neon light tester probably cost less than his multi tester. If you have no use for the multi tester you've saved money.


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RE: GFCI testers - hot to ground question

Im more confused now.

His multimeter was set to checking for voltage.So inserting probes neutral to hot showed 120. But hot to ground tripped the gfci outlet.

So did he have the multimeter on the wrong setting perhaps for it to actually trip? I assumed it would test just like a normal outlet.... is something miswired?


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RE: GFCI testers - hot to ground question

A little further on this ....

My son told me tonight that his multitester has some sort of function on it that adds voltage (I think this was how he put it) to a circuit for certain testing.

I assume its the same function that makes my handy gfci tester trip the outlet.

I apreciate the discussion, I recently took a class at my community center on electricity and electronic basics and its been fun testing and learning. I recomended this forum to the instructor too.


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RE: GFCI testers - hot to ground question

The GFCI reads both the hot and the neutral, if they are the same there is no problem. Testing the hot and neutral shows the same to the GFCI, testing hot to ground only the hot shows voltage and nothing on the neutral, hence, it trips.


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RE: GFCI testers - hot to ground question

Your son is full of crap. I have never seen any tester that "adds voltage" (other than meters set to measure resistance which you would be a damned fool to connect to a live circuit). As pointed out, if the meter will pass more than 30ma to a ground, it will trip the GFCI. Most digital meters are designed with **WAY** higher impendence over 10 Kohms. Some other testers (mechanical wig wags, lights, or meters with a Low-impedence setting) will be enough to trip the GFCI when connected between HOT and some connection (other than the other wire being measured by the GFCI).


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RE: GFCI testers - hot to ground question

My son told me tonight that his multitester has some sort of function on it that adds voltage (I think this was how he put it) to a circuit for certain testing.

Your son is full of crap.
Some other testers (...meters with a Low-impedence setting) will be enough to trip the GFCI

Perhaps her son has a meter with at "low impedance setting"?


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RE: GFCI testers - hot to ground question

That's almost certainly the case (if the thin is even a meter, he just said "multi tester" which could be one of those mechanical voltage sensors).

Still it's not "adding voltage" to anything. That's not how you test a GFCI anyhow. Adding voltage in itself won't trip a GFCI.

Still his son is also full of crap, a Fluke 117 or some other Low Z meter will cost 100 times what the little cheesy outlet GFCI tester will.


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RE: GFCI testers - hot to ground question

Posting from my moms (grandmum) acount this sunday.

My fluke 113 is a LO-Z 3kq meter and triped the GFCI hot to ground immediately.

Brad - Grandmums full of crap son.


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RE: GFCI testers - hot to ground question

I regret that I once again responded to grandmum since my response was not accepted. Had planned to avoid these threads.
I disagree with the stated 30 ma trip level. It is actually in the range of 6 ma.
If a voltmeter requiring that much current (or more) is connected from ungrounded conductor to the equipment grounding conductor, the GFCI will trip. If by chance there is already some leakage creating a lesser ground fault the additional draw of the meter could be enough to carry the draw to over 6 ma.


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RE: GFCI testers - hot to ground question

30ma is the maximum it is allowed to pass.


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RE: GFCI testers - hot to ground question

The link is to a UL website. They are one of the standards organizations and are the source that I used for the information I posted. The GFCIs (Class A) used in residences are for protection of personnel.
It is true that GFCI (GFPE) is used for protection of equipment. The trip level of that type is 30 ma. But that type GFCI is not the type used in the typical single family residence.

http://www.geindustrial.com/Newsletter/Spring05Ground.pdf

This is where GFPE is required.

Here is a link that might be useful: UL

This post was edited by bus_driver on Mon, Nov 4, 13 at 14:21


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RE: GFCI testers - hot to ground question

You're quite right, it's 6ma...actually I had arc faults on the brain.


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RE: GFCI testers - hot to ground question

The tester fondly called a "Wiggy" probably draws enough power to trip a GFCI or an AFCI. My Wigginton is rarely used but is as valid for testing as it ever was. It gives an audible indication as well as visual.
My favorite tester consisting of two 15 watt incandescents in series also trips GFCI and AFCI if the leads are placed Hot to Ground. The tripping is not always convenient if testing for the presence of voltage. But it is a quick way to identify the circuit if the GFCI or AFCI is in the panel.- look for the tripped device.


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RE: GFCI testers - hot to ground question

woa nelly, hold the bus.. Correction.
First of all, a residential type gfi receptacle installed for personal protection has a 3 to 6 milli amp trip rating. 30 ma is a gfi for equipment protection. That 30 ma is high enough to kill you across your heart. A GFCI functions by comparing the difference between the current traveling on the hot conductor as compared to the current traveling on the neutral conductor. Any difference is assumed to be going to ground, regardless of how. That can be established under a safer de-energized condition. The GFI's job is to CYA in the event of a failure by de-energizing the affected circuit. When your son used his meter to trip the GFI, he essentially took the hot conductor to ground, bypassing the Neutral and creating an imbalance on the circuit of greater than 6ma resulting in the opening of the internal switch in the GFI. Can't be to good for the life expectancy of the meter as it is creating a dead short.


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RE: GFCI testers - hot to ground question

dudley, your correction is quite out of order. If the correction is directed to me, nothing I posted is different from your "correction".
The part about tripping range of 3 ma to 6 ma is also wrong. 250 feet of NM-B cable will typically have a leakage to ground of 2 ma or fractionally more. Set at 3 ma , the nuisance tripping in some installations would be intolerable. And that would result in widespread tampering to defeat or disable the GFCI.
Given that volunteers are few for determining the current level required to kill humans, it is generally believed that the level at which the sickliest and most vulnerable among us would be killed by electric current is ABOUT 10 ma and that even the hardiest specimens would be dead at 30 ma.3 ma is felt by most individuals and 6 ma is perceived by most as a very unpleasant shock.
An additional hazard of electric shock is the possible injury that might occur from trying to reflexively escape the situation. I know one man who is partially paralyzed as a result of falling from a ladder when he received a shock while messing with something he knew nothing about-- but somehow thought that he did.
I now I offer a correction. "Can't be to good for the life expectancy of the meter as it is creating a dead short." The described use of the meter is exactly how one would measure voltage. If the meter is set for the correct function, how would that damage the meter?

This post was edited by bus_driver on Tue, Nov 12, 13 at 14:09


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RE: GFCI testers - hot to ground question

As pointed out I've already corrected myself on the 30MA vs. 6MA issue. I had 30MA in my head as that is the leakage an AFCI would trip at.

I agree (for this thread) with everything Bus_Driver has said.


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RE: GFCI testers - hot to ground question

I have one of the three prong testers. When I use the test button on the gfci, the outlet trips. When I use the tester it doesn't. I replaced the gfci outlet and nothing changed.

Its unlikely that the ground isn't working since the outlet is attached directly to the circuit box via a receptacle. I want that outlet to provide gfci protection for the rest of the circuit.

Is there something else that can cause this problem or should I write if off to something about how the tester

Shouldn't a simple bulb tester trip the gfci if you put the wires between hot and ground? Or is that not enough current?


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RE: GFCI testers - hot to ground question

Sounds very much like the ground is, in fact, not connected despite your non-sensical second paragraph.

You should start your own thread rather than tacking on to someone else's problem.


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RE: GFCI testers - hot to ground question

"Its unlikely that the ground isn't working since the outlet is attached directly to the circuit box via a receptacle."
I am highly suspicious of this post. Poster registered today and posted nonsense on another post. But just in case this is a serious request, there is confusion about "outlet" and "receptacle" which can be cleared by some online research. The indicated operation of the tester is typical when used on a nongrounded circuit. The GFCI protects the same on nongrounded circuits. GFCI protection is not dependent on grounding.


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RE: GFCI testers - hot to ground question

I will post separately. I didn't realize that was the protocol.


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