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Author Topic: How much fun (shock) can we have without tripping our GFCI  (Read 10276 times)

Jonathan Johnson

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Re: How much fun (shock) can we have without tripping our GFCI
« Reply #40 on: November 30, 2015, 05:08:49 pm »

And the package says "Test Monthly" but I've never seen anyone test one except for me. And I generally just test them once a year when I change all my smoke detector batteries.

And do you ever test the tester? Nobody hears the dog that doesn't bark.

In the case of the buttons on the GFI, it *should* be a failsafe test; a failure mode where the test button causes the reset button to pop out as normal but protection isn't working -- or the hot terminal is not disconnected -- is highly unlikely.
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Stop confusing the issue with facts and logic!

Stephen Swaffer

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Re: How much fun (shock) can we have without tripping our GFCI
« Reply #41 on: December 01, 2015, 12:20:33 am »

Well this just got more interesting... If I touch my new improved ground wire to the GFCI outlet frame the gfci trips. ????? This is with nothing plugged into the outlet...  My NCVT confirms that the ground is really no/low voltage.

The outlet tests and resets properly. This seems like a pretty obscure fault if the outlet is faulty.

JR

I am curious-is the outlet frame connected to the receptacle grounding screw?  I wonder if somehow it is not happy if the frame is grounded but the ground screw is left "floating".  This should never happen in a good install, so it might be a reason to prevent using it that way?

As for testing GFCIs, the "test" button is really your only safe option.  Since code allows GFCI's to be installed without an EGC if none is present, the "enhanced" 3 light testers with the GFCI test button really aren't always right as they will never trip a GFCI that has no EGC.
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John Roberts {JR}

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Re: How much fun (shock) can we have without tripping our GFCI
« Reply #42 on: December 01, 2015, 09:41:42 am »

I am curious-is the outlet frame connected to the receptacle grounding screw?  I wonder if somehow it is not happy if the frame is grounded but the ground screw is left "floating".  This should never happen in a good install, so it might be a reason to prevent using it that way?
First it tripped when I touched my add-on ground wire to face plate screw.  I then ASSumed that perhaps there was a short between one of the outlet wires to the junction box. So I removed the GFCI from the box and it still trips..  I decided to swap out the GFCI with a spare I had around, and it still behaves the same... (there is a slender chance I put the old one back in because I looked away when I had both laying on the counter and wasn't sure which is which. ) :-\ :-[
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As for testing GFCIs, the "test" button is really your only safe option.  Since code allows GFCI's to be installed without an EGC if none is present, the "enhanced" 3 light testers with the GFCI test button really aren't always right as they will never trip a GFCI that has no EGC.

Applying logic to this, based on my understanding of how things work, this really has to be a FAULTY GFCI outlet. (while it happily powered my coffee maker this morning).

I just measured with my high impedance VOM and I see 113 Vac on the outlet ground tab.  :o :o

After my coffee kicks in, I'll re-engage. I don't like to mess with electricity before I am fully awake.

I report back later, this shouldn't be all that difficult. Hopefully I just mixed up the two GFCI outlets when I thought I was swapping it out, and it's just a simple(?) outlet fault.

JR

PS I tested my new improved ground wire with my way too sensitive NCVT and it is cold, as it should be.
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John Roberts {JR}

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Re: How much fun (shock) can we have without tripping our GFCI
« Reply #43 on: December 01, 2015, 12:32:10 pm »

And do you ever test the tester? Nobody hears the dog that doesn't bark.


While your advice was correct, you appear to be answering some other post.

It turns out my prototype outlet tester is tripping the GFCI.  ??? I'm not sure exactly what is going on but I also smell the distinctive odor of burning resistor and the proto board is getting hot... This particular proto has a bunch of extra parts patched in to test the 100M input Z, and may have too small of an effective resistor in the ground leg. The board is too small and parts are too close together to tell exactly which part is causing the excess heat dissipation.

Without the outlet tester plugged in I still measure 2 mA leaking into the ground (with kitchen appliances plugged in.). Oddly it remains unchanged at 2 mA with the mixer plugged in or not, so the mixer is NOT the leakage path.

Found it...   ;D the 2 mA leakage was being caused by a cheap outlet strip that was "protected", so probably a leaky clamp device across the line to ground (?). Seems like a clamp should be line to neutral but I'll take it apart later. 

=====

I have other work to do but now I can drop the GFCI outlet back into the junction box and ground it.  8)

My next generation outlet tester PCBs are due in a few days from now... currently at the DHL sorting center in Shenzhen.

So logic has returned to this exercise and the laws of physics and house wiring are sorted. I've tested the outlet testers with GFCI before so this appears to be a fault specific to this one prototype tester. I sent away all my other testers, but never smelled the burning resistor smell before. And the field testers have not reported issues with GFCI. The design is specifically running ground current at less than 5 mA.

In fact the UL spec for outlet testers that I am designing to defines the max ground current at 2 mA, so unlikely to trip a 5 mA GFCI.

JR
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John Roberts {JR}

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Re: How much fun (shock) can we have without tripping our GFCI
« Reply #44 on: December 07, 2015, 02:07:32 pm »

I am slowly coming to the realization that my current outlet tester has some extra parts added to ignore the 2mA current that was leaking into the ground of my previously floating kitchen outlets.

I need to start removing those spare parts from my tester. If a similarly leaky power strip causes a hot ground indication, that is probably good to know. In hindsight I shouldn't have fixed that power strip (removed the protection components).

JR
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Re: How much fun (shock) can we have without tripping our GFCI
« Reply #44 on: December 07, 2015, 02:07:32 pm »


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