gfic

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KIRKBRO

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new mexcio
A friend of mine is in journeyman classes he wanted a book of questions to help him learn the code,we meet once or twice a week and review this book and his class work. one question was if a hair dryer fell into a sink of water would it kick the gfic, I said yes book said no because the sink was plastic. My inspector, said no because hair dryer cordcap was only 2 prong, no neut. to gnd. situation for gfic to react to. I thought water neut. and hot wire(120), SHOULD get togeaher, and kick off something hopefully the gfic.
 

stickboy1375

Senior Member
Location
Litchfield, CT
Nope. you need to know how a GFCI works, it looks for a unbalance, so if the sink were plastic, along with the drain, then the gfi would not see a unbalance and thus not trip, stick your hand in the water and thats a differnt story, now the current has a another path to follow and the GFI will detect that.
 

charlie b

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Lockport, IL
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I agree with Stickboy. But I want to add that the book?s basis for the ?no? answer is correct, and your instructor?s basis for the ?no? answer is wrong. Let me illustrate the difference.

Recall that the GFCI device is at the wall, somewhat distant from the sink. Current will pass through the GFCI, head towards the hair dryer along one wire (call it the ?hot wire? for my purposes), and then it will find two paths to take. Some (most???) of the current will pass through the internal wires and heating elements and motor of the hair dryer, and make its way back to the GFCI on the other wire (call it the ?cold wire? for my purposes). Some of the current will be short circuited somewhere within the hair dryer, and pass from the hot wire directly to the cold wire. From there, it returns to the GFCI. Please note that the total current leaving the GFCI along the hot wire is the same as the total current returning to the GFCI along the cold wire. The fact that some current took different paths along the way means nothing; the totals are the same. That is why, as Stickboy pointed out, the GFCI does not trip.

That is also why your book?s answer is correct. There are no paths for current to flow from the GFCI but not back to the GFCI; so the GFCI sees a balanced current. However, if you put your hand in the water (not recommended), you create a new path. The fact that the cord cap has only two wires, and not a third ground wire, means nothing, so your instructor?s answer was wrong. Current will flow along the hot wire, through you, into the floor and into the dirt, to the ground rod, up the GEC to the service point. The GFCI will see a difference in current from its hot wire to its cold wire, and it will trip. You will get a shock, but not long enough to feel it, and certainly not long enough to do you any harm

 

mdshunk

Senior Member
Location
Right here.
JohnJ0906 said:
I seem to recall that Joe Tedesco has a video of a hairdryer merrily "blowing" away fully submerged in a sink of water. Anyone have a link?
He took that video down, but he has one up now of a appliance leakage current indicator tripping. (different than gfci).
 

KIRKBRO

Member
Location
new mexcio
.Thanks for the replys do know how gfic works,and understand no unbalanced in current. All the stress over gfic and they won't work until you force the issue, by sticking your hand in the water a natural reaction when dropping anything in the water, seems we can do better than this. in our industry,,, agin thanks kirkbro P.S going to buy a hair dryer and see let you know.
 

iwire

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Location
Massachusetts
KIRKBRO said:
All the stress over gfic and they won't work until you force the issue, by sticking your hand in the water a natural reaction when dropping anything in the water,

When it is a person making the path to ground they will always get a shock before the GFCI trips.

The GFCI can not predict a ground fault it can only react once a ground fault is established.
 

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
Apparently the water is not conducting electricity. If it were, some of the current from the hot leg would take the water's route to ground and the imbalance would have tripped the GFCI. I could see a balance after the faucet was turned off, but not while the water was running.

Odd....maybe electricity can't flow upstream....

:cool:
 

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
stickboy1375 said:
Nope. you need to know how a GFCI works, it looks for a unbalance, so if the sink were plastic, along with the drain, then the gfi would not see a unbalance and thus not trip, stick your hand in the water and thats a differnt story, now the current has a another path to follow and the GFI will detect that.

Are you sure?

Please explain where that path to ground may be. Through the linoleum or the tile? I would think that if the person was standing on bare concrete with no shoes on or touching a grounded piece of metal there would be a path to ground, otherwise not.

Removed Experiment

As a much safer experiment will show, water does NOT conduct electricity. Take a glass of filtered or distilled water and stick the probes of an ohm meter in it. Take the reading. Now, put a teaspoon of salt in it, stir it up and check it again. Note the difference of conductivity. What you are seeing is the conductivity of the Sodium, a metal, as it becomes an ion dissolved in the water. The water in our bodies are full of dissolved minerals, mostly Sodium and Potassium, but there is also Copper, Zinc, Silver and other trace minerals, all which conduct electricity.

We can also determine in a relative manner if our drinking water has minerals in it or not by comparing the conductivity of it compared to filtered or distilled water. Not all bottled water is mineral free. Check the label, you may be surprised to see that mineral salts are added as 'flavor enhancers'.

In addition, there was a comment made about getting a shock if your body does trip a GFCI. That is not always true as I have done it without getting a shock. There are some variables involved but the GFCIs would not be of much use if they delivered a shock prior to tripping.
 

George Stolz

Moderator
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Location
Windsor, CO NEC: 2017
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Service Manager
I have deleted (or more accurately stated, moved) a decidedly off topic and curious sidebar from this thread. You may direct your derision at me via PM, if so inclined.
 

don_resqcapt19

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Staff member
Location
Illinois
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retired electrician
Mark,
In addition, there was a comment made about getting a shock if your body does trip a GFCI. That is not always true as I have done it without getting a shock. There are some variables involved but the GFCIs would not be of much use if they delivered a shock prior to tripping.
That is not possible. There must be a ground fault with at least 4 to 6 mA of current flowing before the GFCI opens the circuit. You may not have felt the shock, but it happened, or there was a ground fault path that did not include your body that caused the GFCI to open.
 

K8MHZ

Senior Member
Location
Michigan. It's a beautiful peninsula, I've looked
Occupation
Electrician
don_resqcapt19 said:
Mark,

That is not possible. There must be a ground fault with at least 4 to 6 mA of current flowing before the GFCI opens the circuit. You may not have felt the shock, but it happened, or there was a ground fault path that did not include your body that caused the GFCI to open.

I guess I considered a 'shock' as something that caused pain or discomfort, rather than just being a conductor, which I have been *many* times over the years and most of the time I felt it!

That being said, GFCIs do serve a purpose and I feel much safer using them than not, even though it has been proven a hair dryer in the sink won't make them trip.
 

iwire

Moderator
Staff member
Location
Massachusetts
K8MHZ said:
GFCIs do serve a purpose and I feel much safer using them than not,

Of course. :)

even though it has been proven a hair dryer in the sink won't make them trip.

It's been proven that a GFCI does not protect against issues outside of it's design, that is what we would expect.

A GFCI is not designed to trip without a a fault path.
 
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