On Wed, 29 Nov 2006 00:22:47 -0600, wrote:

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 ????

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