If it's a GFCI "outlet" it shouldn't if the short is only between hot
If its a GFCI "breaker" in a panel, then it of should trip on a short of
low enough impedance to cause the current to exceeed the breaker's trip
Could you elaborate? Is it that the insulation on the wires inside
will be damaged by the high pressure, or that you'll just end up
wedging some dust/dirt in even deeper, where it will cause more
Agreed. The OP is being wise IMO. While one sees GFCIs not recommended
for other circuits that supply motors; fridges etc. the fact that it
worked OK for many years and now doesn't seems to indicate the OP is
doing the right thing to question and check.
Thanks for everybody's input.
I replaced the GFI today and still have the same problem. I'll try
cleaning the motor (with compressed air!) and see if that works. TS
Fay has dropped a foot of rain around here the last four days, and
though the wires and motor are protected, maybe there's dampness I
I'll let you know if it works.
On Sat, 23 Aug 2008 15:07:33 -0700 (PDT), unklerichie
I'm about the furthest thing from an expert, but for clarification,
the fan is on the same circuit as the GFI's, but not plugged into the
GFI, right? Are there other loads running on the GFIs when they trip?
40" fan is pretty big, it could just have a big, fat turn-on surge,
but how long as this been going on? And is the fan plug two or three
prong (presume three). And have you checked the ground to the fan
To answer a couple of your questions...
My fan has no plug on it. It's wired from a wall switch. I have
other things running on the same circuit (a few outlets and an 8'
fluorescent shop light). My fan trips the GFI whether there are
additional loads on the circuit or not. It doesn't seem to make a
difference. I used my compressed air to blow out the motor and it
didn't help. When I first posted, I mentioned that the fan would run
for ten seconds and then trip the GFI. The 'ten seconds' only
happened the first couple of times I tried it. Since then, it trips
immediately. I think I've successfully ruled out the GFI (replaced),
the wall switch (replaced), and the wiring from the GFI to the switch
to the fan (all closely inspected). I suppose it's time to have the
motor serviced. If anyone is interested, I'll post the outcome later.
Thanks for everyone's help.
I removed the fan motor and tested it on the benchtop. It's
definitely bad. I replaced it with a 1/2 hp motor I had laying around
(original was 3/4 hp), same rpm's, but the 1/2 has a heck of a time
getting the fan moving. I don't know enough about motors to attempt
that repair myself.
So I decided that's enough of this project. Despite everybody's
assistance, I gave up, went on Grainger's site and ordered a new fan.
The new ones are so much more efficient (much more cfm's at lower
rpm's) , 2 speed, and the one I ordered includes a shutter, a luxury I
don't currently enjoy.
That's why there is a (fairly expensive) device called a megaohmmeter
or "megger" which will apply a selectable DC voltage (e.g. 300V or
600V) and measure the resistance. Using it between the hot and frame
of a motor is a good way to test for insulation degradation in the
motor windings. (Never use the megger between the hot and neutral of
an appliance or load, they aren't designed to run on 300V DC!)
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