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Title: How much fun (shock) can we have without tripping our GFCI
Post by: John Roberts {JR} on October 19, 2015, 12:34:04 pm
I installed a GFCI to my (ungrounded) kitchen outlet next to my sink. Yesterday I was using my trusty old kitchen-aid mixer and experienced a new shock. With the mixer turned off (but still plugged in), I felt a shock between one hand touching the metal mixing bowl (grounded to the mixer), and the metal facing strip on my wood (formica?) kitchen counters.

The metal trim is not grounded or energized (it shouldn't be). Using my neon lamp probe, one lead grounded to my hand, I get dim readings on line and ground, but dark to the metal trim (so apparently it isn't energized).

But I measure 112V with my VOM between the mixer chassis and that metal trim strip.   :'(

It was enough current to be unpleasant, but not enough to trip my GFCI (5mA)...  ;D Time to take the mixer apart and inspect the mains wiring. I don't read any DC resistance, but enough capacitance to feel it.  :o

JR

PS: maybe the mixer has a stinger cap?
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: Geoff Doane on October 19, 2015, 01:01:14 pm
The metal trim is not grounded or energized (it shouldn't be).
JR



The strip must be grounded, isn't it?  Try measuring the resistance between it and a known ground.  Or maybe the capacitance?

GTD
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: John Roberts {JR} on October 19, 2015, 01:16:05 pm
I'd have to run a wire all the way to my panel to make a real measurement (sorry not going to happen). No DCR or C  to my cold water pipe under the sink... (but I haver a plastic water feed from the meter to house since my steel pipe rusted out).

I am pretty sure humans can perceive low current shocks (I have).

Counter and metal trim probably has capacitance to real ground.

JR
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: David Buckley on October 19, 2015, 04:46:14 pm
Yeah, pretty much any double insulated appliance I can rub the back of my hand on it and feel the presence of electricity, its not a shock, or a tingle, more like an odd surface texture.  And the current is very low, it is just capacitive leakage.

Of course, if you want to experiment, then perhaps a Big Clive tingle-tron (http://www.bigclive.com/tickle.htm) might be what you need.....
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: John Roberts {JR} on October 19, 2015, 05:25:53 pm
Yeah, pretty much any double insulated appliance I can rub the back of my hand on it and feel the presence of electricity, its not a shock, or a tingle, more like an odd surface texture.  And the current is very low, it is just capacitive leakage.

Of course, if you want to experiment, then perhaps a Big Clive tingle-tron (http://www.bigclive.com/tickle.htm) might be what you need.....
I don't want to experiment more, I want to cook without unexpected shocks... Yes it was actually the back of my hand so at first I ignored it, but after the next time I stopped ignoring it.  ???

JR

Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: Stephen Swaffer on October 19, 2015, 10:33:42 pm
I'd have to run a wire all the way to my panel to make a real measurement (sorry not going to happen). No DCR or C  to my cold water pipe under the sink... (but I haver a plastic water feed from the meter to house since my steel pipe rusted out).

I am pretty sure humans can perceive low current shocks (I have).

Counter and metal trim probably has capacitance to real ground.

JR

FWIW, for safety metal water piping should be grounded to the panel anyway especially if you have an electric water heater.
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: Jonathan Johnson on October 20, 2015, 01:11:43 am
I felt a shock between one hand touching the metal mixing bowl (grounded to the mixer), and the metal facing strip on my wood (formica?) kitchen counters.

Topic swerve: traditionally, the metal facing strip is used with linoleum as the countertop material. (I mean actual linoleum, the product made with linseed oil, wood flour, and burlap. Not vinyl flooring that some people call "linoleum.") Considering the age of your house, if the counters haven't been redone in 60 or 70 years, the countertops very likely are linoleum instead of Formica. Linoleum is making a comeback both as flooring and as a countertop material.

Linoleum is softer than Formica. Linoleum can be cut with a knife; Formica cannot, though it can be scored with a sharp point.
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: Frank DeWitt on October 20, 2015, 12:51:28 pm
It seems that the metal mixing bowl is electrical connected to the mixer but the mixer is not grounded.  (It is not plugged into a grounded outlet and may or may not have a grounded plug)  (My Kitchen aid mixer has a three wire cord.)

Isuspect that either because it has a grounded plug, or because it is old, or both, it is not double insulated.

The metal counter trim is not grounded.

Man gets a shock between the two.

ACTION REQUIRED.

If it were me I would get a ground into that kitchen even if i had to use wire-mold.  I would put a three wire cord on the old mixer and I would ground the counter trim.  Then I would bake a cake.




Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: John Roberts {JR} on October 20, 2015, 01:11:24 pm
It seems that the metal mixing bowl is electrical connected to the mixer but the mixer is not grounded.  (It is not plugged into a grounded outlet and may or may not have a grounded plug)  (My Kitchen aid mixer has a three wire cord.)
yes metal bowl is grounded to ground pin on outlet. Outlet wiring does not include a ground wire, so sundry appliances plugged into the same strip can have their grounds energized by the mixer's leakage. 
Quote
Isuspect that either because it has a grounded plug, or because it is old, or both, it is not double insulated.
I do not expect it to be double insulated, while I do not read any DCR between line or neutral to ground I do measure some capacitance that I suspect is the cause of shock and measured voltage into the high impedance VOM.
Quote
The metal counter trim is not grounded.

Man gets a shock between the two.

ACTION REQUIRED.

If it were me I would get a ground into that kitchen even if i had to use wire-mold.  I would put a three wire cord on the old mixer and I would ground the counter trim.  Then I would bake a cake.
My plan is to take the mixer apart and determine where it is getting the capacitance coupling to safety ground. I may just need to clean out some smutz (technical term) from inside the mixer. It is a couple decades old.

If it has an actual stinger cap to ground inside I may remove that or rewire it line to neutral.

I already have this on a GFCI outlet so I am protected from dangerous shock (>5mA), but it can still be annoying.

JR

PS: I do plan to add a real ground to the outlet in my laundry room that is literally a few feet from my fuse panel. My dishwasher also plugs into that outlet. It would not be a huge project to snake a ground wire through the dishwasher hole to add a real ground, but for now I just plan to take the mixer apart. 
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: Mike Sokol on October 22, 2015, 09:52:34 am
yes metal bowl is grounded to ground pin on outlet. Outlet wiring does not include a ground wire, so sundry appliances plugged into the same strip can have their grounds energized by the mixer's leakage.  I do not expect it to be double insulated, while I do not read any DCR between line or neutral to ground I do measure some capacitance that I suspect is the cause of shock and measured voltage into the high impedance VOM....

I already have this on a GFCI outlet so I am protected from dangerous shock (>5mA), but it can still be annoying.


OK, now I'm not suggesting this as a real fix until we all think it through, but can you just add a "Stinger Cap" on the back of your kitchen GFCI between the Neutral and Ground screw? Of course, you'll need to verify that the Hot and Neutral aren't swapped in the walls, but that's easy enough to do with a NCVT.

This is more than just a question for your own "mixer" issue. At the University where I teach there's a bunch of practice rooms with 2-banger "ungrounded" wall outlets, and the students are always using ground-lift adapters on their practice amp power plugs or breaking off the ground pins on the power cords. I've told the University they need to replace these outlets with GCFI's, but we still get a lot of buzzing in the practice amps since the chassis are floating. Of course, if they all used modern double-insulated practice amps it would be safe and probably not buzz, but many of my students are finding old tube guitar amps in pawn shops (because they sound great) and bringing them into school. What would an inspector think about this stinger-cap GFCI mod? I've never seen anything in the NEC about stinger caps to create a a capacitor coupled ground for buzz mitigation, but that's essentially what it would be doing.

Thoughts?
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: John Roberts {JR} on October 22, 2015, 10:52:01 am
That's interesting... My cheap GFCI are a tight fit inside those junction boxes but I can experiments with external shunts.

In theory, a 0.15 uF cap from neutral to ground would shunt the nF level leakage inside my mixer.

Let me think about this...

JR
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: Mike Sokol on October 22, 2015, 12:28:59 pm
That's interesting... My cheap GFCI are a tight fit inside those junction boxes but I can experiments with external shunts.

In theory, a 0.15 uF cap from neutral to ground would shunt the nF level leakage inside my mixer.

Let me think about this...

JR

Easy enough to try with a standard Hubble type Edison plug with a 0.15 uF cap connected between the Neutral and Ground screws. Plug that into the outlet or the power strip and it would shunt all the stray voltage leaks to the neutral bus. Of course, this needs to only be used on a GFCI outlet since this stinger cap by itself won't trip a circuit breaker or protect humans from not-to-chassis fault currents. But maby a GFCI plus a Stinger Cap would do the job.

Again for those out there reading about this. DO NOT experiment with this kludge on your own until we determine the safety and legality of such a hookup.   
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: John Roberts {JR} on October 22, 2015, 12:44:42 pm
Easy enough to try with a standard Hubble type Edison plug with a 0.15 uF cap connected between the Neutral and Ground screws. Plug that into the outlet or the power strip and it would shunt all the stray voltage leaks to the neutral bus. Of course, this needs to only be used on a GFCI outlet since this stinger cap by itself won't trip a circuit breaker or protect humans from not-to-chassis fault currents. But maby a GFCI plus a Stinger Cap would do the job.

Again for those out there reading about this. DO NOT experiment with this kludge on your own until we determine the safety and legality of such a hookup.
Yup... I did that already, and it only knocks down the measured voltage between mixer chassis and counter top metal strip from 112VAC to 40VAC...

I still need to take apart my mixer and see what I find. Larger than 0.15uF at 60Hz could couple more than 10 mA so not universally safe for humans, while better than hard wire bootleg ground.

0.15uF or less bootleg cap would prevent any harm from open neutral energizing ground.

JR
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: Mike Sokol on October 23, 2015, 10:14:50 am
A 0.15uF or less bootleg cap would prevent any harm from open neutral energizing ground.

Since a 0.1uF stinger cap would produce a fault current just below 5mA at 120 volts and 60 Hz, is that a valid way to create a safe bootleg ground when added to a GFCI without an EGC? I just don't like floating chassis with voltage on them, even if the fault current is limited by the GFCI tripping. And a lot of my old tube gear WANTS some sort of ground reference to stop the buzzing, even if it's a "stinger cap. Again, one would have to confirm the neutral side of the two wires in the receptacle, but that's simple enough to do even with a neon bulb.

Something like this, perhaps?
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: John Roberts {JR} on October 23, 2015, 11:50:24 am
My use of 0.15 uF in that path is to both keep current below human thresholds for getting stuck, while still high enough to reliably trip GFCI in case of a fault.

The GFCI spec is 5mA+/-1mA so I targeted over 6 mA while less than 10 mA.

JR

caveat lector: these are 60Hz-115VAC numbers.... so not applicable for other countries.
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: Lyle Williams on October 23, 2015, 12:21:55 pm
"The National Electrical Manufacturers Association conducted a national field test and issued the results in January 2001. It found that 14 percent of circuit breaker GFCIs and 8 percent of receptacle GFCIs were nonoperational."

GFCI's provide a great opportunity to save lives when things go wrong.  They aren't nearly reliable enough to trust on their own.
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: John Roberts {JR} on October 23, 2015, 12:30:31 pm
"The National Electrical Manufacturers Association conducted a national field test and issued the results in January 2001. It found that 14 percent of circuit breaker GFCIs and 8 percent of receptacle GFCIs were nonoperational."

GFCI's provide a great opportunity to save lives when things go wrong.  They aren't nearly reliable enough to trust on their own.
That's probably why they have test buttons built in....

JR
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: Mike Sokol on October 23, 2015, 12:32:37 pm
That's probably why they have test buttons built in....

JR

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.

Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: Stephen Swaffer on October 23, 2015, 12:45:23 pm
Just ordered some GFCIs from my distributer and he was trying to remember part numbers-they all changed because there is a new self diagnostic standard they have to meet. I don't know the particulars-but in some ways a GFCI is a GFCI just like a PC is a PC.  Something made is in 2000 or 2005 or whatever is not the same as what you buy today.  They may look the same on the outside but what's Inside is what counts.
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: John Roberts {JR} on October 23, 2015, 01:38:56 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.
Not to veer off my own thread but speaking of smoke detectors, my old detector was a few decades old, and they are so cheap I decided to replace the entire detector with this years battery.

The 25-30 year old detector worked when I moved it out to my tool room and I was making some serious smoke cutting wood dowels for my drum tuner supports. Roasting coffee did not make enough smoke to wake it up.

The new smoke detector mounted in the same location in my hallway, went of about a week ago when I finally turned on my central heat in the living room. No visible smoke, but I could smell a summer's worth of dust being cleared from the heat pump... probably a resistive heat element since the heat pump probably doesn't get that hot.

The new smoke alarm is far more sensitive than the couple decades old one, it replaced. Best $5 I spent lately. Only slightly annoying but more reassuring to know how sensitive it is.

JR   
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: Jonathan Johnson on October 23, 2015, 05:13:48 pm
Not to veer off my own thread but speaking of smoke detectors, my old detector was a few decades old, and they are so cheap I decided to replace the entire detector with this years battery.

Smoke detectors are supposed to be replaced every 10 years. I replaced all the detectors in my house when we moved in during spring of 2012. A month ago I had to replace one because it started false alarming.
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: Bob Leonard on October 26, 2015, 06:22:37 am
John,

This is the kitchen, surrounded with water, multiple appliances, all types of chances to kill yourself with electricity. Why not run a new #12 cable from the kitchen to the panel?
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: Mike Sokol on October 26, 2015, 07:37:55 am
John,

This is the kitchen, surrounded with water, multiple appliances, all types of chances to kill yourself with electricity. Why not run a new #12 cable from the kitchen to the panel?

My son is a chef, and one of the first things I gave him in college was a NCVT and showed him how to test all those metal surfaces for voltage. Commercial kitchens are more dangerous than rock stages because, just as you noted, there's lots of metal appliances and tables, plus water is everywhere.
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: John Roberts {JR} on October 26, 2015, 10:00:16 am
I am not going to rewire my house, and hope the GFCI will prevent serious harm, but the energized mixer ground, even at very low current is annoying.

Yesterday I took the back off the mixer and see a lot of energized metal parts associated with the motor speed switch out in the open. There was also a fine coating of black/gray powder everywhere, probably from motor brushes after decades of wear.

Since a stinger cap to neutral doesn't squash this voltage completely (only drops to 40 VAC) I am really tempted to pull a separate ground wire from my panel..maybe 15' away but through a wall.  Wont be pretty but I don't feel like completely tearing down the mixer... A solid ground could possibly clear the leakage path or just catch fire.  ;D

JR

PS: I already plan to ground the outlet in my laundry room that my washing machine is plugged into. My dishwasher cord goes through the wall to plug into that same outlet. Not crazy to run a new ground wire through the hole into the kitchen.

PPS: Of course my NCVT says the mixer is hot, but it says all my kitchen appliances are hot so not very helpful.
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: Stephen Swaffer on October 26, 2015, 01:50:17 pm
One other option would be to do like I habitually do anytime I step onto a farm site. Slip on a nice heavy (dry!!!) pair of leather gloves. If it is wet or hot enough to make gloves sweaty get out the voltage rated gloves.  Not always convenient, but the older I get the more allergic I am to lectricty.


Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: Jason Lavoie on October 26, 2015, 02:04:03 pm
No DCR or C  to my cold water pipe under the sink... (but I haver a plastic water feed from the meter to house since my steel pipe rusted out).

Any chance your panel was solely grounded to the water system (it happens), and now that ground is floating?

Jason
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: John Roberts {JR} on October 26, 2015, 02:36:33 pm
Any chance your panel was solely grounded to the water system (it happens), and now that ground is floating?

Jason

No there is a proper ground wire from my meter panel straight down into the earth. I know the distro is grounded from my miswired extension cord and enertgized chassis sump pump in my wet yard.  :o
======
Sorry I can't see wearing heavy leather gloves just for operating my kitchen mixer..

JR
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: David Buckley on October 26, 2015, 06:45:36 pm
Something like this, perhaps?

No, not some random cap found on eBay.  A cap that is connected from line to ground should be a Y rated cap, which are designed for this sort of application.
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: John Roberts {JR} on October 26, 2015, 07:26:47 pm
No, not some random cap found on eBay.  A cap that is connected from line to ground should be a Y rated cap, which are designed for this sort of application.
yeah, that too... but wrong value first...wrong type next... The 0.15uF i used to confirm that it didn't work was A) only 100V, and b) not a Y cap...   Am I in trouble? (no not still plugged in.)

I did a search for 0.15uF Y caps for my stinger GFCI drop and that apparently is not a common value for that technology cap (most are smaller values).

But I am still looking because that is the value it needs to be to meet my dual requirements (>5 mA and <10mA at 120VAC-60Hz to trip the GFCI while doing no harm to the meat puppets)
 
JR
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: Mike Sokol on October 26, 2015, 08:02:26 pm
No, not some random cap found on eBay.  A cap that is connected from line to ground should be a Y rated cap, which are designed for this sort of application.

I'm not suggesting Line to Ground. This would be connected Ground to Neutral. ;D  I know that's a small distinction, but you're probably correct. So where do you buy Y-rated suppression capacitors? I've been looking around but don't see a source.
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: John Roberts {JR} on October 26, 2015, 09:40:32 pm
I'm not suggesting Line to Ground. This would be connected Ground to Neutral. ;D  I know that's a small distinction, but you're probably correct. So where do you buy Y-rated suppression capacitors? I've been looking around but don't see a source.
Y caps are available but not very common that large value.
Just looked at digikey and biggest Y2 or Y3 rated caps are 4700 pF

Still looking

JR
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: Mike Sokol on October 29, 2015, 07:06:08 pm
i showed a pic of JR's advanced outlet tester at AES today, and the concept was well received. But several attendees came up after the presentation and asked where they could buy one. So?????
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: John Roberts {JR} on October 29, 2015, 10:14:48 pm
I am trying to get a good partner company interested... So far it doesn't seem promising... If I have to I can do this myself, just not looking forward to the UL approval. I wouldn't sell these without that.

I can probably make these until somebody rips it off... It needs to be out there...

JR

PS: Yesterday I took one of my prototypes to check out a few outlets in a storage shed my neighbor built. He did the wiring himself. Two outlets coming down from the roof over an open air sink (for cleaning fish), and one outlet inside the storage room. All had correct polarity, but only one of the three has a ground connection.
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: John Roberts {JR} on October 30, 2015, 01:09:14 pm
OK... After letting my fingers do some walking I have determined that the UL standard covering my tester is UL 1436 which I can buy for only $400 in pdf or $500 for hard copy...  ::)

This will not be cheap to do right... and UL1436 references a half dozen other standards so I won't know until I get this how much more it could cost just to see the specs.

JR
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: David Buckley on November 04, 2015, 06:13:06 am
I'm not suggesting Line to Ground. This would be connected Ground to Neutral. ;D  I know that's a small distinction.....

This is one of those funny, political things.  In the USA, the terms grounding and grounded are (confusingly) used to identify the neutral and earth, and there is this thing that they are the same.  In pretty much every other non-110V country, in regulatory terms, the neutral is required to be treated as a "live" conductor, and thus there is no distinction between N/G and N/G, they are both "live" to ground, and both require the use of Y rated caps.  (There is also an X rated cap to go between L and N)

Try Newark for Y rated caps; Newark is now the USA arm of Element 14, formerly known as Farnell Electronics, and they definitely know what a Y cap is.
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: John Roberts {JR} on November 27, 2015, 12:44:34 pm
I just received my 100' of wire so I can string a separate ground from my panel to my washing machine/dishwasher outlet , and kitchen outlet. This should either eat the leakage from my mixer or burn it up... either result is acceptable.

I have a spare GFCI that I plan to use in the washing machine/dishwasher outlet so I'll be GFCI and grounded there after I finish this project.  Hopefully this weekend.

JR
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: John Roberts {JR} on November 30, 2015, 01:17:31 pm
Update, while not a final installation I just pulled some wire through the dishwasher hole and grounded it to a fuse panel screw.

Using my trusty VOM I measure 2 mA current coming from my mixer chassis to that real mains ground. Not enough current to trip the GFCI by itself (5mA +/-1), 2 mA certainly reduces that operating margin.

I wonder if that 2 mA changes over time? Only 1/4W of power dissipation.

JR

PS: my metal counter trim strip measures open circuit resistance to ground but 0.75 nF
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: Mike Sokol on November 30, 2015, 04:47:26 pm
Update, while not a final installation I just pulled some wire through the dishwasher hole and grounded it to a fuse panel screw.

Using my trusty VOM I measure 2 mA current coming from my mixer chassis to that real mains ground. Not enough current to trip the GFCI by itself (5mA +/-1), 2 mA certainly reduces that operating margin.

I wonder if that 2 mA changes over time? Only 1/4W of power dissipation.

JR

Everything (any everyone) leaks a little... and the older we get, the more we leak.  ;D
PS: my metal counter trim strip measures open circuit resistance to ground but 0.75 nF
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: Jonathan Johnson on November 30, 2015, 05:03:27 pm
Everything (any everyone) leaks a little... and the older we get, the more we leak.  ;D

I find that as I get older, my overnight capacitance gets lower and lower.
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: John Roberts {JR} on November 30, 2015, 05:04:02 pm
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
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: Jonathan Johnson 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.
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: Stephen Swaffer 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.
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: John Roberts {JR} 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. ) :-\ :-[
Quote


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.
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: John Roberts {JR} 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
Title: Re: How much fun (shock) can we have without tripping our GFCI
Post by: John Roberts {JR} 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