GFCI testing question.

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JohnJ0906 said:
If you push the test button, and there is still voltage, the GFCI is bad.
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How does the average home owner who's "supposed" to test them monthly know that it's still hot even though it snapped??
 
stickboy1375 said:
Your correct in your thinking, the problem is how would a two wire tester create that imbalance without the ground? Answer that question and you have your answer.
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They can't design a GFCI tester to work like a GFCI test button????
 
wptski said:
They can't design a GFCI tester to work like a GFCI test button????
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Where is the ground path that the tester will utilize? The test button shorts (with a resistance) from load hot to line neutral. This bypasses the measuring electronics, and creates an imbalance on the load side - current goes out on the load hot, but doesn't return on the load neutral - imbalance. The plug-in tester can't do this.

As I posted before, use an extention cord plugged into a receptacle that has an EGC, and use a wiggy, if you can't trust the GFCI.
 
JohnJ0906 said:
Where is the ground path that the tester will utilize? The test button shorts (with a resistance) from load hot to line neutral. This bypasses the measuring electronics, and creates an imbalance on the load side - current goes out on the load hot, but doesn't return on the load neutral - imbalance. The plug-in tester can't do this.

As I posted before, use an extention cord plugged into a receptacle that has an EGC, and use a wiggy, if you can't trust the GFCI.
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So in a ground fault, where does the fault scurry to in two-wire? It's not through the ungrounded? Are you saying I have this all wrong? Won't be the first, but if you tell me a GFCI will NOT work on two-wire, you just had my ass handed to me:confused:
 
76nemo said:
So in a ground fault, where does the fault scurry to in two-wire? It's not through the ungrounded?
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Right, it's through a person most normally. That would be one silly tester, wouldn't it?
 
A GFI receptacle will work on a two-wire circuit.

But a GFI PLUG-IN TESTER will not work on a two-wire circuit. These testers connect the hot to the ground (using a resister to create a load). In a two-wire system, even if you have a grounding receptacle with no ground wire, they will not trip the breaker because there is no ground for the plug-in tester to connect to.
 
JohnJ0906 said:
Where is the ground path that the tester will utilize? The test button shorts (with a resistance) from load hot to line neutral. This bypasses the measuring electronics, and creates an imbalance on the load side - current goes out on the load hot, but doesn't return on the load neutral - imbalance. The plug-in tester can't do this.

As I posted before, use an extention cord plugged into a receptacle that has an EGC, and use a wiggy, if you can't trust the GFCI.
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Where does a diagram show that there is any circuit bypassed by the test button? Unless the diagrams posted in other threads lately are too basic.
 
A GFCI device has access to the neutral ahead of the sensor core, but a plug-in tester does not, so it requires an outside reference.

Another way to test a GFCI is to use a well-grounded volunteer.

Stated by Larry Fine.

Now I understand. Thanks to all who responded. I needed to hear it in that fashion, now I can sleep:wink: Talk about frustration! It's not easy being simple:rolleyes: That was the answer I was looking for Larry. Thanks a bunch!!!!!!
 
480sparky said:
Try clicking here.
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Thanks for the slide show! Interesting graph also which I've seen before about trip time of "typical" GFCIs. Not all are within typical values shown.

I see the point now which is mentioned in the post just above. The location of the neutral test point in the GFCI showing the 15K resistor.
 
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480sparky said:
Try clicking here.
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My thanks as well, 480. Pages 38 and 41 raise a question in my mind, however. On page 38, they state that using a GFCI tester on a 2 wire circuit can be dangerous, without saying how or why. Then on page 41, the question "What if there is not equipment ground....? Such as in a 210-7(d)(3) application?" appears but is never answered. Any idea why the use of a tester would be "dangerous? (I've seen inspectors use 'em on more jobs than I can count). Also, any thoughts on the Art. 210 reference?:confused:
 
lbwireman said:
My thanks as well, 480. Pages 38 and 41 raise a question in my mind, however. On page 38, they state that using a GFCI tester on a 2 wire circuit can be dangerous, without saying how or why. Then on page 41, the question "What if there is not equipment ground....? Such as in a 210-7(d)(3) application?" appears but is never answered. Any idea why the use of a tester would be "dangerous? (I've seen inspectors use 'em on more jobs than I can count). Also, any thoughts on the Art. 210 reference?:confused:
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Since I didn't write it, I can't answer for them. But a plug-in GFCI tester will not work on an ungrounded receptacle.
 
480sparky said:
Since I didn't write it, I can't answer for them. But a plug-in GFCI tester will not work on an ungrounded receptacle.
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Sorry 480, I should have been clearer in my post. My intention was to thank you for the link to the NEMA slideshow, not hold you accountable for its' content. Beyond that I had hoped that you or some of the other folks on the forum might have some thoughts as to why it might be "dangerous" to use a tester on a "2-wire circuit" (presumably using a 2 prong/3 prong adapter), as well as any thoughts on the Article citation. Most of our work is service, upgrade and retrofit in an area where the majority of the occupancies are more than 50 years old, so I encounter and have a particularly keen interest in grounding and bonding issues. One of our most common "bread and butter" jobs is device replacement under '05 Art. 406.3(D)(3)(b)&(c) which used to be 210.7(D)(3), so I was interested to know if anyone had any ideas as to why the question might have been put in the NEMA document (and then left unanswered). No offense was intended.:smile:
 
To complicate matters there were a bunch of counterfeit GFCIs made in China that weren't actually GFCIs. They were just outlets that had a trip and reset button. If you pressed the test button they would 'trip'. Because of that, many inspectors are now using plug in testers to test installed GFCIs.

http://forums.mikeholt.com/showthread.php?t=92134

Harbor Freight was selling GFCI receptacles for less than 3 bucks apiece. Anyone here think they were safe?
 
In older resi occupancies, we often find loooooong #14 runs with voltage drop well in excess of code recommendations. In the course of analyzing the existing circuits, this tool has been worth it's weight in gold (even at today's prices).
View attachment 1425
It's primarily a "line load simulator" which lets us check voltage drop (as VAC and %) under known loads (10A, 15A & 20A) at any outlet. Since the tool also incorporates a GFCI Test function, the "dangerous" reference to GFCI testers used on "2-wire circuits" in the NEMA slideshow provided by 480sparky caught my attention. My question upthread was posted in the hope that someone would have some insight as to why NEMA might have made this statement. Any thoughts will be appreciated.
 
The safety problem with using a GFCI tester on a circuit that does not include an EGC is the fact that the tester will put 120 volts via a resistor onto the EGC. If the device being tested is a 3 wire receptacle and there is a load that has a 3 wire cord plugged into the other half of the receptacle when you use the tester the case of the item that is plugged in will be energized at 120 volts.
 
don_resqcapt19 said:
The safety problem with using a GFCI tester on a circuit that does not include an EGC is the fact that the tester will put 120 volts via a resistor onto the EGC. If the device being tested is a 3 wire receptacle and there is a load that has a 3 wire cord plugged into the other half of the receptacle when you use the tester the case of the item that is plugged in will be energized at 120 volts.
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Or if you use one of those old 2-prong adapters with the short green wire with the fork crimped on the end....
 
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