DIYbanter - View Single Post - I thought the GFI was supposed to trip ?????

Jeff Wisnia

wrote:

Jeff Wisnia wrote:

wrote:

wrote:

wrote:

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 ????

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

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.

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

D

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
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.

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).

Makes sense to me...I've encountered more than enough cases of GFCI
breakers tripping because of cruddy conditions along the circuit to
become an advocate of just using GFCI 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

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
The speed of light is 1.8*10^12 furlongs per fortnight.