In article , BobK207 wrote:
On Dec 26, 1:06 pm, M Q wrote:
HerHusband wrote:

I am skeptical that a properly working fan should trip a properly
working GFCI when the fan is turned off. If there is no ground fault
in the fan or switch, there can be no imbalance of currents (conservation
of electrons).

This is incorrect; see an earlier post regarding the collapse of the magnetic
field in the motor windings when power is switched off. The consequent
backcurrent generated does indeed produce a brief, slight current imbalance.
This is evidently of sufficient magnitude and duration to exceed the GFCI's
trip threshold.

A double pole switch should not make a difference.

Of course it should. By opening both the neutral and the hot, a DPST switch
prevents the backcurrent from reaching the GFCI, thus preventing the GFCI from
ever seeing the imbalance.

I might suggest an intermittent ground fault in the
fan or switch when the fan is turned off.

Perhaps; but the explanation referenced above is IMO much more likely to be
correct.

Please let us know what the problem is/was when/if you figure it out.

Give MQ's theory a try. I would agree with his suggestion that you
might have an intermittent ground fault in the switch itself.

Very doubtful. Given that it's a single-pole switch, this would require an
intermittent, high-resistance short to ground that doesn't draw enough current
to make an audible arc. Hard to imagine how that could happen.

Cheap & easy to try it out. Just swap the switch with another SPST
from somewhere else in the house.

Easy enough to test -- but the results are predictable: it won't make any
difference.

It's possible that this particular GFCI is a little more sensitive than it
should be, and swapping it with a different one may cure the problem.

Switching both the hot and the neutral through a double-pole switch is almost
certain to fix it.

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.