You basically have a 2 wire inductor. You are saying that when the circuit is broken, magnetic field collapse produces a current flow in one wire that is not equal to the current flow in the other wire. You may be in line for a Nobel Prize. Or maybe not.
Pay attention this time. The currents _at_the_GFCI_ are unequal, because one of the two wires is not connected to the GFCI.
I think that YOU need to pay attention: In the wire that is not connected we can agree that the current is zero? In the wire that is connected, what do you think the current is? If it is zero, they are equal and the GFCI should not trip. If it is not zero, where do you think that current is going? Those electrons have to go (come from) somewhere. They are not getting stored in the fan. They could be going to ground, but only if you have a ground fault.
Of course.
Small, but non-zero.
Correct.
To ground, obviously, at the service entrance.
Electric current is the movement of electric *charge*. The current is generated by the collapsing magnetic field.
True.
False. All current in the neutral wire ultimately goes to ground at the service panel.
... or anything else, for that matter (except one side of the switch).
MQ-
Sorry for the potentially redundant post but......
Since the GFI is tripping we know that somehow the currents compared by the GFI's circuit are different; the hot is zero since the switch is open, thus the current at on the neutral is non-zero.
Any current produced in this way will be way too small to trip the GFCI. The capacitance to ground of the now open hot wire bewteen the motor and the switch is way too small to support the required current. If this theory was correct then the GFCI could be made to trip by applying line voltage across the motor from a separate branch circuit, one on the same leg, while the switch is open. Back emf is voltage, not current.
Though I applaud the effort.
How about static discharge from their finger to the switch when they go to turn it off?
I considered that, but the GFCI trips even if I just touch the switch handle (no metal conductive parts).
It will sometimes also trip three or four times in a row. Trip, reset, trip, reset, etc. Then it'll go several weeks without tripping again.
The GFCI, switch, wiring, and fan are all new. I've already replaced the GFCI and switch to rule those out as faulty. Everything is properly wired and grounded.
My in-laws live out of town so I don't get up that way very often, but I'm going to try the double-pole switch on our next visit. If that fails, it has to be a faulty fan, or a problem with the wiring.
Anthony
Actually it sounds like a wiring issue. Conductors have an inductive/ capacitive link between them. If you have a stray conductor running a different load that is close to and parallel to the wires feeding the fan motor, then you'll get a current imbalance through the GFCI.
That doesn't explain why the GFCI trips _only_ when the fan is switched off.
Nope, other than where the cable exits the switch box, there are no other cables anywhere near the cable running to the ceiling fan.
Also, the fan NEVER trips while running, only when it is turned OFF. And even then, it's only once every few weeks or so.
Anthony
Maybe the two effects (motor generator action, and capactive bleeding to ground) are combining thier efforts to trip the GFCI. I don't know. But I do know there are millions of GFCI's out there that don't trip when a motor connected to them is turned off. I also know that if you run more than about 250 ft of extension cord that the capacitive coupling between the hot wire and the ground wire will cause the GFCI receptacle that you have it plugged into to trip.
Capacitive/inductive coupling can lower the GFCI's tolerance by providing a continuous background leakage. If the GFCI is rated to trip at .X amps, then capacitive leakage to ground can reduce that trip current to a small fraction of .X. Any spurious signal is likely to cause a trip at that point, even the neighbors ham radio.
Well, it was worth a try, but the DPST switch did not fix the problem either. It worked fine for about two weeks, then tripped again a couple of days ago.
As always, it trips when the fan switch is turned "OFF", not while it is running.
I've tried two different GFCI's, and three different switches, and they all have the same results.
I'm baffled. The wiring is new and in good condition. The only two things I can think are the fan itself is bad, or condensation is draining back into the fan and causing problems.
Still, it seems like the DPST switch would completely isolate the fan from the GFCI. There shouldn't be any current flow even if there was a problem with the fan. And there have been absolutely no problems while it is running. Only when it is turned off.
Other than rewiring to take the fan off the GFCI, or replacing the fan, are there any other things I could try?
Anthony
Please describe how you wired the DPST switch; post a diagram if possible.
I have a similar problem. I noted that when the light bulb on the fan fixture is illuminated the problem does not occur. Perhaps a resistive load across the fan absorbs any power line spikes which trip the GFCI. Just an idea.
Mike
Note: my return address contains no numeric characters.
As you would expect. The incoming hot wire goes to one pole of the switch, the incoming neutral wire goes to the other pole. Then the switched hot and neutral go directly to the fan.
The ground wire is directly tied to all other grounds.
The switch clearly indicates which two terminals are the "line" and which two terminals are the "load". Outgoing hot wire is on the same pole as the incoming hot wire, and the outgoing neutral is on the same pole as the incoming neutral.
I don't see any other way you could wire the switch?
Anthony
In my case, the fan is just a fan. No light or heater in it.
Wiring is about as simple as it gets. A single incoming 12/2 cable coming from the switch. Fan housing is grounded, hot and neutral are connected according to the fan instructions (black to black, white to white. No brainer).
Anthony
If it's *still* causing the GFCI to trip, then I see only two possibilities:
1) the original GFCI *and* the replacement are defective 2) there is a ground fault in the fan itself.
How quickly after you turn off the swich does the GFCI trip, and how long does it take for the fan to fully spin down?
I can't really think of any. Sorry.
Cheers, Wayne
Instantly as far as I can tell. Flip the switch off and the GFCI trips at the same time.
I don't know. Probably a couple of seconds at least.
Anthony
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