GFCI protection with modern PVC plumbing

[NEC Inspector]

To expand on this question - you are in a tub of water, completely isolated from any grounded object. A plugged-in appliance is tossed into the tub. The GFCI does not trip.

If you are not touching anything grounded, only touching the water touching the appliance or the appliance itself, how would you be part of the circuit? Wouldn't it be like touching a metallic conduit carrying neutral current, where you would only get shocked when you take the conduit apart and are touching both sides? I can see how you would be parallel with the circuit, but how would you be in series?

 

[winnie]

I can see how you would be parallel with the circuit, but how would you be in series?

IMHO you would be part of a circuit that is in parallel with the load.

You would have current flowing from hot to neutral through the load.

You would have current flowing through the very short path through the water inside of the appliance from hot to neutral.

You would have current flowing through longer paths through the water outside of the appliance from hot to neutral.

You would have current flowing through the longer paths from hot through water through your body back to the water and back to the neutral.

Each one of these paths would carry current in inverse proportion to its impedance. Depending upon lots of factors you might or might not get a significant shock and might or might not even feel anything.

 

[jim dungar]

I'd expect that potential of the water to be about 60V,

Measured from where to where? A potential (difference) requires two points.
Coupling capacitance would be the only mechanism that would create a potential between points withouta common reference.

 

[winnie]

Measured from where to where? A potential (difference) requires two points.
Coupling capacitance would be the only mechanism that would create a potential between points withouta common reference.

You are correct, I was sloppy by not specifying.

I was assuming a normal residential service and measuring relative to 'ground' (say the service ground rods) as my arbitrary reference point.

-Jonathan

 

[ramsy]

If you are not touching anything grounded, ..how would you be part of the circuit?

Step potential may increase near source.

Measured from where to where? A potential (difference) requires two points.

If UL required such a test, 1 probe on Neutral may reference different points in tub water, or different points on dummy body parts, which conducts like flesh.

 

[ramsy]

Coupling capacitance would be the only mechanism that would create a potential between points without a common reference.

A test may need to prove if capacitance of 200lbs of conducting dummy flesh switching polarity at ~60Hz, eventually heats up, without being part of the circuit, or having a ground reference?

 

[Joethemechanic]

I dropped the end of an extension cord in a plastic pail and the gfci didn't trip. All I got was a little bit of bubbles from the electrolysis going on.

I have had them trip from an extension cord laying in a puddle on the ground

 

[jim dungar]

I dropped the end of an extension cord in a plastic pail and the gfci didn't trip. All I got was a little bit of bubbles from the electrolysis going on.

I always thought you needed DC to have electrolysis, but evidently it is just extremely more challenging if you use AC.

 

[Joethemechanic]

I always thought you needed DC to have electrolysis, but evidently it is just extremely more challenging if you use AC.

I guess it's not true electrolysis. Maybe water vapor or some reaction with the metals in the cord cap, whatever it is there defiantly is a little stream of bubbles. I would think that theoretically if the frequency was low enough some electrolysis would take place. What if the the frequency was 1hz?