I thought the GFI was supposed to trip ?????

[maradcliff]

I just went to an auction and came home with a whole bunch of old junk. One of them was an old metal framed swivel house fan. I am always leary of that old stuff, so I always test it in a GFI outlet.

I plugged it in, and reached to flip the metal switch. When I touched it, I got a fairly good jolt on my fingers. The GFI did NOT trip. WHY? I thought that was the whole purpose of having them. This GFI was just purchased and installed, and the test button works fine.

Just for the heck of it, I plugged the fan in again, and had the switch already turned on. The fan ran just fine on a wooden table. Then I set it on the cement garage floor and plugged it in again, and the GFI tripped instantly. For the heck of it, I put a piece of wood under it (on the floor) and the GFI did not trip. This proves that fan motor has leakage to the metal housing, so it goes in the garbage. But I can not understand why the GFI did not trip when my fingers got shocked ????

[Paul Franklin]

Evidently the current flow through the fan to your hand, through your body, throught your shoes to the ground was below the threshold of the GFI. That path presented enough resistance to current flow to limit it to a small enough value that the GFI didn't trip. Placing the fan on the floor provided a lower resistance path so he current was high enough to trip the GFI.

GFI's will allow a small amount of fault current to flow without tripping. This reduces nuisance tripping, but still provides protection against dangerous levels of current. There was enough current to feel (which is very little) but not enough to be dangerous.

Seems like the GFI did its job, and you were smart to do the test you did.

Paul

[spamTHISbrp]

head to home despot or lowesers (or better yet a local place) and purchase a little outlet tester.

3 lights indicate the wiring, and a button tests GFCIs. Much better for testing GFCIs than the test button on the outlet.

Also, GFCI breakers are much more sensitive (and faster) than GFCI outlets. I converted a circuit from GFCI outlet to GFCI breaker, just for fun I tested the GFCI outlet on the circuit with the GFCI breaker. Breaker was faster than the outlet.

Dave

[trader4]

The test you did doesn't prove GFCI breakers are more sensitive and faster than GFCI outlets. It just proves that the particular pair you had behaved that way.

To the OP, what were you standing on, type of shoes, etc or in contact with when you got the shock? It does seem that the current you got was less than the amount needed to trip the GFCI.

[scott21230]

I would open up the fan and check to see that the metal casing is actually grounded. Sounds like it's not. It should be.

[spamTHISbrp]

Yes, the test I did was anecdotal, but GFCI breakers are more sensitive.

D

[trader4]

Since it's an old swivel type house fan, it's unlikely it has a grounded cord to begin with. Also, even if it does, you can verify that the case is grounded with a VOM, without taking it apart.

[Warren Block]

Two-prong plug on the fan, right?

The amount of current on the hot line is the same as that on the neutral. So as far as the GFI is concerned, there's no ground fault. It can't tell if it's just the fan motor between hot and neutral, or the fan motor and you.

The cement floor provided a current path to ground, so the amount of current on the neutral was different from what was on the hot. The GFI sees that difference and trips.

[Jeff Wisnia]

Do you happen to know whether this is by design or is it just "always that way"?

And if by design, why?

I wouldn't think it would be difficult for the designers to set roughly equal sensing levels/times in both types.

Jeff

[CJT]

Irrelevant.

The current through his body returns to ground (just like the garage floor test that follows), not neutral.

[trader4]

Certainly seems that the current through the GFCI should be unbalanced. The only way it would be possibile for it to be equal would be if you grabbed one part of the fan that was shorted to hot, and another that was connected to neutral.

[spamTHISbrp]

I have to claim 'just in my experience' based on a few cases, I did read something awhile ago and can't find the darn thing.

One common sense reason to claim the breaker 'more sensitive' though is that the breaker will 'see' more wiring and equipment, and so the background leakage the breaker sees will be higher than that which an outlet will see (even if chained to a few more outlets).

Since the background leakage will be higher, the amount of fault current required to hit the magic number of total leakage current (usually 4-6mA) will be less.

Dave

[Terry]

The first way to check if the case is grounded is by looking at the plug. It has to have 3 prongs to be grounded.

If it is a two prong plug, and it sounds like that is what it is, It will not be grounded.

This was a problem. Most likely you can flip the plug in the receptacle and the "shock" will go away.

The hot is connected to the case in one situation and connected to the switch for the motor lead in the other.

They came out with polarized plugs to assure that the hot is connected to the load first.

[Warren Block]

Pretty clearly not the case since the GFI didn't trip. Unless it's faulty. Or are you saying it's impossible to get shocked between hot and neutral?

[trader4]

Good grief! If that were true, don;'t you think there would be an awful lot of people dead from decades ago? I don;t know of any appliances with a metal case, where if you simply plugged the cord in one way vs the other, you could wind up dead, because the case is now hot.

[trader4]

It's not clear, since the current required to feel a shock may be below the threshold that will trip the GFCI.

Unless it's

[Warren Block]

A web search said about 5 mA to make a GFI trip, so I see what you're saying. I thought they were much more sensitive than that, but if they were they would probably trip too often.

[CJT]

I think you have that backwards.

[CJT]

... or insensitive, which is the issue.

Or are you saying it's impossible to get shocked between hot

[maradcliff]

Cement garage floor, leather shoes that were somewhat wet from walking to the garage after a rain storm. I ONLY felt the shock on my fingers. I was not touching anything with my other hand or other body parts.

Mark