GFCI Tripping Repeatedly?

Page 2 of 4  
On Dec 28, 9:14pm, snipped-for-privacy@milmac.com (Doug Miller) wrote:

With only "one" wire connected to the GFI there is no difference of potential either. It kind of makes induced currents impossible too, but run with it. :)
Want to bet on the double pole switch?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Maybe you ought to spend a little more time thinking about that...

Sure.
--
Regards,
Doug Miller (alphageek at milmac dot com)
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I have to admit, I'm a little skeptical about the double-pole switch. Whether resistive or inductive, how can you have current flow unless the circuit is completed? Open the hot wire and current shouldn't flow through the neutral either, unless there really was a fault in the wiring somewhere? I was an electronic tech MANY years ago, so maybe I've just been away from this stuff too long. :)
In any case, my own attempts at solving the problem have failed, so I'm willing to give it a try. I bought a double-pole switch yesterday ($9) and plan to install it in the next day or two. Unfortunately, due to the erratic nature of the problem, I may not know for a month or more whether it solved the tripping problem. But, if it does trip again, at least I can rule out the switch once and for all.
Thanks for the feedback!
Anthony
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

So test it.

Back-EMF can flow through the neutral wire because the neutral is connected to ground at the breaker box.

Back-EMF from the collapsing magnetic field in the motor windings when it's switched off.

Yep. Let us know what happens.
--
Regards,
Doug Miller (alphageek at milmac dot com)
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Doug Miller wrote:

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.
--
bud--

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@isp.com says...

Pay attention this time. The currents _at_the_GFCI_ are unequal, because one of the two wires is not connected to the GFCI.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
T. Rex wrote:

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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

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.
--
Regards,
Doug Miller (alphageek at milmac dot com)
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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.

It's going from the fan collapsing field thru the neutral wire back to the neutral / ground bus at the service panel.

Actually, they're kinda stored "stored in the fan"......in the magnetic field, while the fan is running.

They are going to ground, but not thru a fault....but thru the neutral wire.
MQ, this is just my understanding of how motors & GFI can interact......... I could be wrong but I believe this is a reasonable theory.
cheers Bob
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

That doesn't explain why the GFCI trips _only_ when the fan is switched off.
--
Regards,
Doug Miller (alphageek at milmac dot com)
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Jan 1, 10:32am, snipped-for-privacy@milmac.com (Doug Miller) wrote:

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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
T. Rex wrote:

... or anything else, for that matter (except one side of the switch).
--
The e-mail address in our reply-to line is reversed in an attempt to
minimize spam. Our true address is of the form snipped-for-privacy@prodigy.net.
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

fan
but
wall).
The fan isn't required to be on a GFI protected circuit unless it is in the shower/tub space. I'm not sure what could be causing your problem. Maybe try installing a two pole switch so that the hot and the neutral are being disconnected at the same time.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Why connect the fan to the GFI at all? Is it a requirement in your locality?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
This is not an uncommon anomaly. As others have said, the NEC doesn't require GFCI protection for the fan unless it's located over the tub, and the manufacturer requires it

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Well, good to know, but a little too late. It had been my understanding that the entire bathroom circuit needed to be protected by the GFCI. But the inspector mentioned a couple of things that didn't need to be on it also. Oh well, no harm done, except for the fan nuisance.
The DPST switch idea sounds like my best option if I can find one.
Anthony
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Site Timeline

Related Threads

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.