Grounding of a sink basin

[mikeb8791]

Looking for everyone's opinion on this: Just sat thru a code update today and the instructor asked the question about all these new sinks out there made of everything you can think of and having a plastic drain tube on it and PEX tubing. The instructor took a clear plastic storage container and filled it partially with water. He took a GFCI outlet tested for proper operation, and then tested it for proper operation. Once it was shown that the GFCI tripped when tested he put on all of his arc flash gear and plugged in a 2-wire hair dryer and dropped it into the storage tank. It did not trip the GFCI. He pulled it out multiple times and the dryer continued to operate. He then took a newer style with a built in GFCI on the end (so there were two devices that should've tripped) and plugged it into the same GFCI outlet. He turned it on and dropped it into the container and it did not trip the GFCI either. After some discussion he took a ground wire for a EG reference and dropped it into the container. Took the dryer, turned it on and dropped it into the water and it finally tripped the GFCI. am I the only one that sees an issue with this? I was told this has been brought up to several individuals in the industry and it has gone nowhere. Any thoughts????.......

 

[Dennis Alwon]

Mike, welcome to the forum. I have done this same experiment with a lamp socket and a wp flood buld. If there is no ground present then the gfci will not trip because a gfci measures the current in and compares it to the current out. Since the current has no where to go except back thru the gfci then the unit does not see any leakage.

If, for instance, there is 5 amps in on the hot conductor and 5 amps goes back on the neutral conductor then the gfci is happy.

 

[oldsparky52]

The GFCI did not trip because all the current was staying on the 2 conductors. If someone had their hands in the water and was grounded somehow (concrete slab?), the GFCI's trip. I don't see this as a problem with GFCI's, now if you didn't have GFCI's, then maybe it is a problem (sink not being bonded).

 

[g3guy]

I understand the question and the replies. And...

Non-metalic sinks have been 'non-bonded' since time immemorial.

I've not read of mass home electrocutions during my 80+ years.

What are we looking for here?

 

[LarryFine]

Think of a non-grounded sink as double-insulated.

 

[petersonra]

A GFCI works by comparing the current in one leg of the circuit with the current in the other leg. As long as the current is the same, no current is being passed through something other than the two circuit conductors (e.g. - some one's body), so there is no reason to trip.

Putting the ground wire in the water caused current to flow into the ground wire so there was a current imbalance, such as when a person gets energized.

This is the way a GFCI is supposed to work.

 

[Dennis Alwon]

As I said earlier I did this experiment. After I dropped the light into a plastic bucket I put my hand in the water. Couldn't feel a thing. You could probably fill up a fiberglass tub and jump into the tub with the lights burning underwater. A little dangerous as you don't want to touch anything grounded.

 

[mikeb8791]

I understood what a GFCI measured but I guess my issue was if a person were to put their hand in the water I would’ve thought they would have received a shock given they were somehow grounded.

 

[hbiss]

After some discussion he took a ground wire for a EG reference and dropped it into the container. Took the dryer, turned it on and dropped it into the water and it finally tripped the GFCI. I was told this has been brought up to several individuals in the industry and it has gone nowhere. Any thoughts????.......

Don't you think that as soon as someone that's in contact with the water touches something that is grounded the GFCI is going to trip?

So what is this guy suggesting? That a non-metallic sink have some sort of conductive area or a metallic drain and that it be bonded to ground? Sounds like a solution to a problem that doesn't exist. I think he should submit it to the NEC.

-Hal

 

[Little Bill]

Lesson for the day!





















Don't put your foot in the sink while drying your hair.

 

[don_resqcapt19]

I understood what a GFCI measured but I guess my issue was if a person were to put their hand in the water I would’ve thought they would have received a shock given they were somehow grounded.

If the person has a path to ground and puts a hand in the water, that person will may receive a shock and if the current of that shock is within the trip range of the GFCI, the GFCI will open the circuit.

 

[GoldDigger]

If the person has a path to ground and puts a hand in the water, that person will may receive a shock and if the current of that shock is within the trip range of the GFCI, the GFCI will open the circuit.

And if for some reason there is a voltage gradient in the water (more likely with a pool or tub than a sink) putting two hands in the water can cause a serious shock, but not a GFCI trip.

Sent from my XT1585 using Tapatalk

 

[hbiss]

And if for some reason there is a voltage gradient in the water (more likely with a pool or tub than a sink) putting two hands in the water can cause a serious shock, but not a GFCI trip.

Not likely with a single point source such as hair dryer and the water isolated from ground.

-Hal

 

[Frank DuVal]

Right, as a voltage gradient by definition means current is flowing. If current flowing is greater than 5 mA, then the GFCI should trip!

Without current flowing, there is no voltage drop.

 

[don_resqcapt19]

Right, as a voltage gradient by definition means current is flowing. If current flowing is greater than 5 mA, then the GFCI should trip!

Without current flowing, there is no voltage drop.

Not with a two wire circuit in a non-metallic basin with no connect to earth. The only path is the same path that every load uses...ungrounded to grounded.

 

[roger]

I understood what a GFCI measured but I guess my issue was if a person were to put their hand in the water I would’ve thought they would have received a shock given they were somehow grounded.

As stated, if they are grounded they would most likely receive a shock (GFCI's do not prevent shocks but hopefully they keep it short) but the GFCI should trip. To create an experiment take a piece of wire and form it into the shape of a human, stick one end in the water and the other end to some grounded object, the GFCI should trip. (Just kidding about forming into the shape of a human)

Roger

 

[Dennis Alwon]

I understood what a GFCI measured but I guess my issue was if a person were to put their hand in the water I would’ve thought they would have received a shock given they were somehow grounded.

If I am wearing rubber soles and use a plastic bucket then my hand in the water will not receive a shock because the current path is from one conductor into the water thru the bulb/dryer and back thru the other conductor. The water itself has the potential for one to get shocked if one is grounded.

In my case,the current cannot flow thru me as there is nowhere for the current to go. If I touched a ground with my other hand then yes I would get a shock but hopefully the gfci would trip before if hurt me.

 

[LarryFine]

A GFCI device is useless on an ungrounded system, and will not function. A person must receive a shock for one to trip.

 

[ptonsparky]

A GFCI device is useless on an ungrounded system, and will not function. A person must receive a shock for one to trip.

I don’t know if I would call it useless as long it trips in a timely manner.

 

[Dennis Alwon]

A GFCI device is useless on an ungrounded system, and will not function. A person must receive a shock for one to trip.

Larry, you will always receive a shock on a gfci but hopefully it will trip before it kills you. On an ungrounded system it can protect you esp. if you are grounded by something else.


A gfci in an ungrounded circuit will not trip with a tester but it can protect a person.