GFCI protection with modern PVC plumbing

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?
 
NEC Inspector said:
I can see how you would be parallel with the circuit, but how would you be in series?
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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.
 
winnie said:
I'd expect that potential of the water to be about 60V,
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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.
 
jim dungar said:
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.
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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
 
NEC Inspector said:
If you are not touching anything grounded, ..how would you be part of the circuit?
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Step potential may increase near source.
jim dungar said:
Measured from where to where? A potential (difference) requires two points.
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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.
 
jim dungar said:
Coupling capacitance would be the only mechanism that would create a potential between points without a common reference.
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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?
 
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
 
Joethemechanic said:
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.
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I always thought you needed DC to have electrolysis, but evidently it is just extremely more challenging if you use AC.
 
jim dungar said:
I always thought you needed DC to have electrolysis, but evidently it is just extremely more challenging if you use AC.
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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?
 
winnie said:
If a running hairdryer falls into an insulated tub, I'd expect that potential of the water to be about 60V, because the water will be roughly equally coupled to both the hot conductor and the neutral conductor. IMHO the 'potential field' of the water would be 120V right near the hot conductor, 0V right near the neutral conductor, smoothly varying between those two values between the conductors, and roughly 60V when distant from the conductors anywhere in the tub.

You will also have a 'current field' in the tub. This current field will be highest right between the two conductors, and will fall of very rapidly as you go away from the two conductors. My hunch is that at distances greater than the spacing between the two conductors the fall off will be faster than inverse square. (The inverse square law strictly applies to point radiation sources, but the electric current we are considering is a near field effect, not radiation, and the source isn't a point.)

But as others have said: if current flows from hot to neutral without any leakage, the GFCI can't detect it.
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The next time my wife replaces her working hair dryer I will come off a GFCI breaker then thru a brand new GFCI temporary receptacle and place the hairdryer into a plastic bucket filled with cold tap water then turn on the GFCI circuit breaker. Will do it outdoors on my driveway 25' from my house. Curious how long it might take to trip. Took apart a few GFCI receptacles years ago and the two line conductors pass thru a torrid coil that if it measures an current unbalance over 4 to 6 ma will trip.
 
My understanding is that electrolytic corrosion of metals is not a problem with AC, because you alternately corrode and replate the metal in the surrounding media.

But intentional electrolysis of water with alternating current is possible, and I believe a few companies are investigating it. One huge problem is that instead of producing separate hydrogen and oxygen streams, you produce a single perfect blend of the two. Not really good for storage :)
 
garbo said:
The next time my wife replaces her working hair dryer I will come off a GFCI breaker then thru a brand new GFCI temporary receptacle and place the hairdryer into a plastic bucket filled with cold tap water then turn on the GFCI circuit breaker. Will do it outdoors on my driveway 25' from my house. Curious how long it might take to trip. Took apart a few GFCI receptacles years ago and the two line conductors pass thru a torrid coil that if it measures a current unbalance over 4 to 6 ma will trip.
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It will not trip, unless the water has a high enough concentration of mineral to trip on short circuit. If you laid it in a mud puddle, then it probably will trip, or if the hair dryer has a three wire cord (very rare)
 
garbo said:
The next time my wife replaces her working hair dryer I will come off a GFCI breaker then thru a brand new GFCI temporary receptacle and place the hairdryer into a plastic bucket filled with cold tap water then turn on the GFCI circuit breaker. Will do it outdoors on my driveway 25' from my house. Curious how long it might take to trip.
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It won't do anything. You can stick your arm in the bucket and it won't do anything.
 
Is a hairdryer waterproof?
How is throwing a appliance in water any different than just cutting a cord plugged into a gfi?
 
I guess if everyone really cared about life-saving issues on this end, shouldn’t every appliance have an isolation transformer

That would alleviate any possible return pass that’s not just the water still ain’t gonna stop you from throwing it. Appliance in the water but nothing‘s gonna stop that would it?
 
The plastic bag or bucket (non metal) is an insulator, unless the appliance has a ground wire, the only current flowing would be hot to neutral, which a gfi will not trip on. OCP maybe if there is a high enough current, but not likely.
 
ActionDave said:
When I thought a first year apprentice class I would put a plugged in power strip into a plastic pitcher and drink out of it. Learned the trick from Mr. Mike Holt.
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If you did that in California, you would have seen the Prop.65 Warning label on the power strip.

You might remember things differently, and fixed your spelling of taught, if avoiding drinking water with chemicals known to cause cancer, birth defects or other reproductive harm.
 
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