Voltage Tester - GFCI's tripping

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Using a low impedance meter between line and ground will trip a working GFCI circuit. This should be expected for obvious reasons.
 
How close was the tester to the GFCI receptacle? It's conceivable that if the tester is close enough to the GFCI, the stray magnetic field from the solenoid could couple into the toroidal transformer of the GFCI to cause it to trip. Particularly when you connect or disconnect it. Try testing the output of a GFCI receptacle with an extension cord on it to see if distance from the GFCI reduces or eliminates the tripping. If it still trips then it's an electrical effect and not a magnetic one.
 
Yes I agree. This test was conducted by connecting the tester to the Hot and to the Grounded conductor. I just poked one lead in the left hand blade slot and the other lead in the right hand blade slot causing the tester to hum as its indicator hovered around the 120V reading. I was concerned the installer had gotten grounded and grounding conductors inadvertently connected somewhere.....until I began to consider the fact that I was testing on a completely separate circuit.....and was tripping multiple GFCI's on different branch circuits. Also, this building is an out-building and the panel is a subpanel fed from a service panel in an adjacent building so the subpanel is fed 4-wire (single phase 120/240V with separate grounded and grounding conductors). Really strange phenomenon. Just curious if anyone out there has experienced this before
 
synchro said:
How close was the tester to the GFCI receptacle? It's conceivable that if the tester is close enough to the GFCI, the stray magnetic field from the solenoid could couple into the toroidal transformer of the GFCI to cause it to trip. Particularly when you connect or disconnect it. Try testing the output of a GFCI receptacle with an extension cord on it to see if distance from the GFCI reduces or eliminates the tripping. If it still trips then it's an electrical effect and not a magnetic one.
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Well now that you mention it....the gfci's that tripped on separate circuits were all within about 20 feet of each other and on #12 copper...just on different circuits. I'll try that and see if it makes a difference. I just cannot imagine why this little tester is tripping GFCI's and a carpenters big circular saw won't trip the circuits at all. Even plugged in a space heater pulling 1500 watts (resistive...not inductive) with no problem at all. Weird.
I will definitely try a long #16 extension cord and see what happens.
 
You were using your tester between the Hot and an Equipment ground. Your heater and the saws are not. It should trip at least the GFCI ahead of it. There are enough posts about inductive loads causing grief with adjacent GFCIs that I am not too surprised.

We were cycling a small AB contactor yesterday that would trip the GFCI receptacle ahead of it, until we put a snubber across the coil.
 
ptonsparky said:
You were using your tester between the Hot and an Equipment ground.
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Nope. I was testing between the Hot and the Grounded Conductor (or Neutral as some call it), not the Gounding Conductor (ground wire). But yes as you stated I think there is some type of inductance generated ghost voltage causing just enough of an imbalance current in the trip coils of the GFCI's to activate them.
It had me worried at first until I had a chance to think through where everything was located it the circuit layouts. Then I realized there really was no other explanation for the trips...especially after doing power tool testing and circuit polarity testing (with my receptacle outlet tester that I later ran out and retrieved).
Thanks for the replies! This further confirms my conclusion that it was the inductance of the tester causing nuisance trips. I was still a bit skeptical of my own conclusion thinking maybe there was something I was missing or not realizing could happen. Being an engineer and not an installer I realize experience trumps most everything else when it comes to these types of problems!
 
RD35 said:
Nope. I was testing between the Hot and the Grounded Conductor (or Neutral as some call it), not the Gounding Conductor (ground wire). But yes as you stated I think there is some type of inductance generated ghost voltage causing just enough of an imbalance current in the trip coils of the GFCI's to activate them.
It had me worried at first until I had a chance to think through where everything was located it the circuit layouts. Then I realized there really was no other explanation for the trips...especially after doing power tool testing and circuit polarity testing (with my receptacle outlet tester that I later ran out and retrieved).
Thanks for the replies! This further confirms my conclusion that it was the inductance of the tester causing nuisance trips. I was still a bit skeptical of my own conclusion thinking maybe there was something I was missing or not realizing could happen. Being an engineer and not an installer I realize experience trumps most everything else when it comes to these types of problems!
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So you are convinced that the inductance from your tester is enough to trip a gfci randomly but the inductance from a power tool is not? I don't buy it.
 
ActionDave said:
So you are convinced that the inductance from your tester is enough to trip a gfci randomly but the inductance from a power tool is not? I don't buy it.
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For our AB experiment we purposely cycled the power to the contactor by rapidly inserting and removing a pigtail to the coil while we monitored the voltage at the coil. A simple insert, pause, remove did not trip the GFCI. Most use of power tools would fall into that category.

I don't use the style of tester he used, but I do have one I inherited from someone, somewhere. Looks like I have something to play with this morning.
Intermittent connection of the tester would be the first thought as to why.
 
"Inductive kickback" sometimes causes GFCI tripping, if it is a solenoid type tester maybe this is what is happening?
 
kwired said:
"Inductive kickback" sometimes causes GFCI tripping, if it is a solenoid type tester maybe this is what is happening?
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That's why I suggested a cord. If it still trips, it's the type of load; if it doesn't, it's the magnetism.
 
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