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Author Topic: How much fun (shock) can we have without tripping our GFCI  (Read 10225 times)

John Roberts {JR}

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Re: How much fun (shock) can we have without tripping our GFCI
« Reply #10 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
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Mike Sokol

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Re: How much fun (shock) can we have without tripping our GFCI
« Reply #11 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.   
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John Roberts {JR}

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Re: How much fun (shock) can we have without tripping our GFCI
« Reply #12 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
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Mike Sokol

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Re: How much fun (shock) can we have without tripping our GFCI
« Reply #13 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?
« Last Edit: October 23, 2015, 11:06:45 am by Mike Sokol »
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John Roberts {JR}

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Re: How much fun (shock) can we have without tripping our GFCI
« Reply #14 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.
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Lyle Williams

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Re: How much fun (shock) can we have without tripping our GFCI
« Reply #15 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.
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John Roberts {JR}

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Re: How much fun (shock) can we have without tripping our GFCI
« Reply #16 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
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Mike Sokol

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Re: How much fun (shock) can we have without tripping our GFCI
« Reply #17 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.

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Stephen Swaffer

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Re: How much fun (shock) can we have without tripping our GFCI
« Reply #18 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.
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John Roberts {JR}

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Re: How much fun (shock) can we have without tripping our GFCI
« Reply #19 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   
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Re: How much fun (shock) can we have without tripping our GFCI
« Reply #19 on: October 23, 2015, 01:38:56 pm »


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