GFCI wired correctly, but the tester fails to trip it

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Old 12-13-15, 05:53 PM
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GFCI wired correctly, but the tester fails to trip it

Hello all! I just installed a new dual GFCI outlet. The test button on the outlet itself trips the outlet, and my receptacle tester indicates that it's wired correctly. However, the GFCI test button on the tester fails to trip the outlet.

Some more info in case it's relevant. I extended some old 12-2 wire that lacks the ground conductor with some new 12-2 wire. In the junction box in which they're tied together, the ground from the new 12-2 is just open. In the new outlet box, both outlets and the line ground are grounded to the box.

Any ideas why the tester isn't tripping the GFCI? The tester is on the cheap side (Southwire brand). Not sure if that's a factor.


Thanks!
 
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Old 12-13-15, 06:04 PM
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Is the outlet box a good ground? Do you have a multimeter that you could use to measure the voltage between the box and the hot wire.

It sounds to me like it is not grounded. I'm not sure what an outlet tester is (though I can imagine) but for it to create a ground fault it would have to, well, create a ground fault. My understanding is that the test button doesn't actually ground the circuit rather it uses some sort of resistor to create a minor variation in current.
 
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Old 12-13-15, 06:14 PM
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Probably just the way the tester is built. That said you have created a serious code violation.
I extended some old 12-2 wire that lacks the ground conductor with some new 12-2 wire.
That is never allowed by code. An ungrounded circuit can not be extended. You need to run a new grounded circuit from the breaker box and remove this extension.
 
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Old 12-13-15, 06:32 PM
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The receptacle tester with GFI trip test..... uses ground to trip GFI.
If the box isn't grounded.... the tester won't trip it.
 
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Old 12-13-15, 06:40 PM
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The 3 light tester shunts a small current to ground. If there is no ground there is no path for the current to go to. The built-in test button is the only recognized test.
 
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Old 12-14-15, 04:29 AM
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Thanks, all. What if, instead of running a completely new 3-wire circuit from the panel, I run just a ground from the junction box back to the panel and ground it there? (A single ground wire tied to the ground wire in the new 12-2, and then follow the path of the old 12-2 back to the panel)

I'm assuming that the panel, at least, is grounded. Hopefully this was standard practice when my panel was installed.

I'm trying to avoid major rewiring, but also certainly want a code-compliant and safe installation.
 
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Old 12-14-15, 07:05 AM
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First things first. Do you have a meter? If not you should have one for testing, a cheap analog can be had for about $15.

Is the box you tapped off of metal? If so, check voltage between the original hot wire and the metal box, if it's ~120V, the box is grounded. Sometimes in older homes the ground wire was attached to the back of the box using a nut and machine screw.

A longshot maybe but I've found a hidden ground many times.
 
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Old 12-14-15, 08:19 AM
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Let me first agree with most of the posts above.

It's not code compliant to extend an existing two wire circuit. It is compliant to convert two prong outlets to three prong outlets by using GFCIs.

As mentioned, the only approved test for GFCIs is the internal test button. GFCIs trip by sensing an imbalance greater than 5mA between load hot and load neutral. It's assumed that if there's imbalance, the current's going to ground: either through the ground pin, through another ground connection (water pipes) or through you (BAD!).

Using the outlet tester (which shunts load hot to ground) will not work without a ground. The GFCIs self test feature shunts the neutral current back to line neutral causing the imbalance.


What if, instead of running a completely new 3-wire circuit from the panel, I run just a ground from the junction box back to the panel and ground it there? (A single ground wire tied to the ground wire in the new 12-2, and then follow the path of the old 12-2 back to the panel)
Code allows several ways to run a new ground wire: including back to the panel or to a ground rod or water pipe ground (w/in 5 ft of entry to the house). This only applies if everything's interconnected. Just installing a ground rod near the junction box does not count unless that ground rod is tied into the other ground rods.

However, if your area has adopted the 2014 version of the National Electric Code, you may connect a ground wire to a grounded circuit that originated in the same panel as your ungrounded circuit.

This page goes into it in a little more detail complete with the code references in 250.130(C):
electrical - Is it OK to borrow a ground wire from a different circuit? - Home Improvement Stack Exchange
 
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Old 12-14-15, 08:36 AM
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Thanks, Handyone. But unfortunately, there is definitely not a ground with the old wire or the old box. The wire and the box were exposed and only had the old 2-wire 12-2 entering the old metal box. This metal box had no ground of any kind. I replaced it with a new plastic one.
 
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Old 12-14-15, 10:57 AM
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For the same effort you could add a new grounded circuit as grounding the old receptacle .
 
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