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[Jonathan Johnson]

We can stick a fork in this one...

Sorry, no can do. All my forks are 4-prong, and all my outlets are 3-prong.

[Mike Sokol]

Sorry, no can do. All my forks are 4-prong, and all my outlets are 3-prong.

Guess I should have predicted this, but there's a band named "Fork In An Outlet" and their tunes are available at an on-line radio.

[Chris Hindle]

Sorry, no can do. All my forks are 4-prong, and all my outlets are 3-prong.

Get thee a TRIDENT.

[John Roberts {JR}]

While far from definitive, my rat shack VOM measures off scale MOhms of resistance from either neutral or hot to ground, but does measure 0.27 nF from one pin and 0.13 nF from the other to ground so some minor capacitance but well low on the shock hazard scale.

======

I just returned from the store with my brand spanking new electric kettle. The best that $12.92 can buy at Walmart. I am pleased to note that my new kettle has a two wire line cord so should be pretty thin leakage to my ground now.

JR

PS: Don't plug in a fork with your bare hands... if a metal fork you could be shocked.

[Stephen Swaffer]

Silly question-did you test the GFCI?  Don't need to lose any forum members!

[John Roberts {JR}]

Silly question-did you test the GFCI?  Don't need to lose any forum members!

I appreciate the concern but no..

Since you asked I just tested both of them... and they both dutifully tripped and then let me reset them. 

The .2 nF capacitance would be way lees than a mA (more like 10 uA).. Surprised I could feel the tingle at all, and at first I wasn't sure it was electrical (I'm old and sometimes nerves just fire for no reason) but I measured 100V so did not grab it again.

I feel it was pretty harmless capacitance in the old kettle, but the new one is better with no ground lead at all to leak current into all my other appliances.

JR

[Mike Sokol]

I used to do this a long time ago to check for leakage current in test gear, so perhaps it's time to dust it off for testing hot chassis fault current. If you put a 1,000 ohm resistor between the suspected hot-chassis and an earth/ground connection, then measure the AC voltage across the resistor,  you'll read approximately 1 volt per mA of fault current.

This is an important thing to know since these hot-chassis conditions can be divided into three different categories. High-Z/Low-Current, Mid-Z/Mid-Current, and Low-Z/High-Current.

A High-Z/Low-Current hot-to-chassis fault may have only a few mA of ground fault current available, and sometimes less. This is what a lot of electricians call a phantom or ghost voltage because it disappears when measured with an analog meter that loads down the hot chassis voltage. Even a properly operating appliance with an open EGC can exhibit a High-Z/Low-Current fault since virtually all power supplies have small amount of leakage. And a stinger cap in an old guitar amp can provide a High-Z fault as well.

A Mid-Z/mid-current fault can have tens to hundreds mA of leakage current available. Old guitar tube amp transformers and leaky capacitors can easily cause this condition. This fault can give you a good jolt and perhaps even cause heart fibrillation, but it's not enough to trip a circuit breaker. However, it should be sufficient to trip a GFCI.

A Low-Z/high-current fault is essentially a short circuit between the hot side of the line and the chassis. Could be caused by a pinched wire, shorted stinger cap, or burned transformer windings. It can supply up to the circuit breaker current to the fault path. However, a human is typically 1,500 ohms or so (hand to hand) so a shock victim will typically only draw around 100 mA from a Low-Z fault. The bad news is that just 30 mA for a few seconds is the danger area where ventricular fibrillation can occur.

The thing to realize is that ANY voltage (more than 2 or 3 volts) between the chassis and earth is a warning sign that the EGC path has been compromised. Once that occurs, anything goes. 

[Steve M Smith]

Found it..... the leakage path is a 3 wire plug electric kettle plugged directly into the GFCI outlet

First, the obligatory warning: !! Don't try this at home !! (even though I did).

Many years ago I had a washing machine which would more often than not, trip out the power.  As the machine was merely about twenty five years old and was a hand me down from my mother when she bought a new one and it had only been repaired by me half a dozen times before, I was loathe to replace it with a new one.

I traced it to a high resistance/low leakage from the heating element to the grounded outer cover.  Whilst I had the machine open, A thought crossed my mind: "what if the leakage was at the live end of the element?".  So I pulled off the wires from the terminals and swapped their positions.

It turned out that I was probably right as I had now moved the bad area closer to neutral.  The machine continued working for another five years before it was finally retired.


Steve.

[Stephen Swaffer]

Heating elements are a common source of "leakage" to ground.  I suspect they are responsible for most of the "deaths by microphone" that happen in baptismal pools.  The 2014 NEC now requires that dishwashers be connected to a gfci circuit-I was told that the reason was that manufacturers could not make the dishwashers safe for non-GFCI circuits.  I am guessing this is likely due to heating elements and too much plastic in the design to provide an effective ground fault path.  Since nothing makes a homeowner upgrade to GFCI,  I wonder how many older homes getting new dishwashers will have the circuit upgraded to GFCI?

As more and more plumbing systems become entirely plastic, heating elements are creating more potential hazards.

[John Roberts {JR}]

It seems to me that a much cheaper implementation of GFCI could be accomplished by original equipment manufacturers if designed in from scratch. If heating elements are a known problem engineer that problem away.

I have mixed emotions about government mandating such changes, and while the calculus sounds a little cold, how many housewives have been electrocuted by their dishwasher? If one brand kills a bunch of housewives, the class action lawyers will sniff them out and make bad design more expensive than good.

That same calculus applies to my recent pet project of electrocuted guitar players who also sing... clearly not enough for a class action.

JR

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