GFI won't trip
- Thread starter dale46
- Start date
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Sierrasparky
Senior Member
- Location
- USA
- Occupation
- Electrician ,contractor
There is no ground so the tester is not making a connection to ground for the test.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
A GFCI receptacle's test button works by connecting a resistor from the hot wire after the current sensor to the neutral ahead of the current sensor, which mimics someone receiving a shock.
A plug-in GFCI tester works by connecting a resistor from the hot wire after the current sensor to the ground wire, because it has no way of accessing the neutral ahead of the current sensor.
No ground connection results in no shock-mimicking current. Note that a ground "cheater" (3-prong to 2-prong adapter) with the ground tab or wire grounded, will allow a plug-in tester to function.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
Yes that's it and that is one reason why you should only be using the test button to test the GFCI receptacle in the first place. Those plugin testers can actually give you a shock if the conditions are right. Larry has a nice explanation as to why one method (the device test button) works and the other doesn't.
JFletcher
Senior Member
- Location
- Williamsburg, VA
All 3 prong receptacles that are GFI protected but only have two wire circuits should have stickers on them that read "GFI Protected / No Equipment Ground". I would guess that part of the reason for this is because when you put a plug tester in such a receptacle, it will not trip the tester... The only way to test those receptacles properly is to trip the Upstream GFI and verify power is dead.
GFI receptacles and Breakers work perfectly well with two wire systems, the ground wire is irrelevant for their operation
GFI receptacles and Breakers work perfectly well with two wire systems, the ground wire is irrelevant for their operation
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
that is the way it should be. the plug in testers are pretty much useless for testing the GFI part of a receptacle. use the test button on the receptacle.
Thanks for the input. I didn't realize those GFI testers test between hot and ground.I thought they tested between hot and neutral mimicking how the device actually works.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
The neutral slot on the receptacle is after the internal circuit monitor so no plugin tester will connect before it leaving only the EGC for it to send the test current.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
The reason for the stickers is to give code making panel and inspectors a warm fuzzy feeling. Typical user has no clue what they mean.
Any current between the "hot" and "neutral" of the receptacle or "load terminals" is seen as normal expected load. Any current that leaks outside that path is abnormal, and once it exceeds 4-6 mA trips the device. The test button sends test current outside the protected path, one side of "line" conductors to opposite side of "load" conductors". This path is outside of the current transformer that monitors the intended current path.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
Well, there is another way. I use my solenoid tester to check for GFCI protection by plugging one probe in the receptacle's hot slot and grounding the other probe. Anything from an extension cord to a nearby sink's faucet (presuming metal piping) to any nearby grounded surface will work.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Digital meter with a low impedance setting works also. Or any load you can imagine over 6 mA connected to a point inside and a point outside the GFCI protected circuit will trip it.
This includes getting the "hot" from elsewhere and the "neutral" via the GFCI protected circuit.
- Location
- Illinois
- Occupation
- retired electrician
I think the real reason for those stickers is 250.114....something no user has any clue about, and most inspectors don't either. They added Informational Note #2 following 406.4(D)(2) in the 2017 code to call attention to the requirements in 250.114.
K8MHZ
Senior Member
- Occupation
- Electrician
So much for the notion that the NEC 'ends at the receptacle'.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
I'll stand by what I previously said. Electricians will see that sticker and realize there isn't an EGC, they might even say to themselves 'someone must know the codes'. Most users won't know or care what that sticker means. Inspectors will be happy because code was followed though it didn't really matter one bit on this one.
JFletcher
Senior Member
- Location
- Williamsburg, VA
I had a home inspector write up the GFCI receptacle in the kitchen did not trip with his tester, even though it was marked with those stickers, and the GFCI not only work, it was one of the new self-testing ones as well.
Other people's children....lol
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Don't confuse the "self testing" feature with the procedure of pressing the test button, they are not the same thing. Pressing that test button actually creates a real unbalance current condition and the device should mechanically open the circuit.
The self test feature is constantly monitoring the electronics of the device for whatever malfunctions it was designed to detect (find it hard to believe it can detect and act upon all possibilities but can be designed to work for many foreseeable possibilities) and will lock itself out should it fail self testing. Failure of self testing from what I know usually means the device needs replaced, there is no resetting after such failure.
Old GFCI's when failed to function, would often continue to allow power to pass through, with no GFCI protection.
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