# Fan tripping GFCI



## AllanJ (Nov 24, 2007)

If you move the switch handle slowly, you get a bigger spark at the switch contacts inside, although I do not see why this shoulld trip a GFCI.


----------



## secutanudu (Mar 15, 2009)

AllanJ said:


> If you move the switch handle slowly, you get a bigger spark at the switch contacts inside, although I do not see why this shoulld trip a GFCI.


Yeah, maybe an AFCI...

The switch is a double-switch. The bottom half controls the shower light, which doesn't appear to trip anything. 

I did all the wiring for my 2 bathrooms myself, except connecting the fan. I ran the wires right to the fan, then the contractor who is building it for me connected the wiring after running the duct (I wasn;t home).I can't imagine he messed up connecting 2 wire-nuts. even so....that would have nothing to do with the switch, right?


----------



## Yoyizit (Jul 11, 2008)

secutanudu said:


> If I flip the switch quickly it doesn't trip. Any idea what that might be?


You need a new switch. 
If the hysteresis in the switch is working it wouldn't allow so-called 'teasing'.


----------



## secutanudu (Mar 15, 2009)

Ok - I'll try a different one. It's brand new, too. Maybe I'll just switch the fan to a timer and use a double-switch for my main light/shower light. I sure hope that's the problem!


----------



## secutanudu (Mar 15, 2009)

FYI: The switch is a "decora" version of this:


----------



## vtboy51 (Apr 1, 2009)

I've got the same problem, sometimes when I turn off the bath fan, it will trip a gfci that is "downstream" of the switch. I've read other post that say this can happen because of the motor in the fan, causing a small power surge when being turned off, also can happen with ceiling fans. Not sure of the fix, some say that different gfci have slighty different trip points, you could try another one, it might not be quite as sensative.


----------



## secutanudu (Mar 15, 2009)

vtboy51 said:


> I've got the same problem, sometimes when I turn off the bath fan, it will trip a gfci that is "downstream" of the switch.


Do you mean "upstream"?


----------



## vtboy51 (Apr 1, 2009)

I have my power from the panel entering the light/fan switch box, in that box I'm splicing a feed that goes to power to a gfci outlet on the other side of the bathroom. The fan switch is essentially tied to the LINE side of the gfci.


----------



## secutanudu (Mar 15, 2009)

Hmm, my fan is on the load side. How does anything on the line side trip the gfci? A bank teller doesn't know if someone robs you in the parking lot on the way out 

I believe you....just don't understand.


----------



## vtboy51 (Apr 1, 2009)

I've been wiring for 15 years, and never have seen this either. I'm not sure why a surge on the line side would cause it to trip. It's possible that the gfci looks for surges on the load, line, and on the actually plugins (this is considered the load side also) . If someone can better explain, I'd appreciate it.


----------



## Chucky Jesus (Jul 21, 2009)

*Me too. Fan upstream of GFCI trips...*

I have power directly from the panel running into a junction box. In this junction box, I have a double switch like the one picture above, with each switch supplying power to one duct fan. One 14/2 exits this box and supplies four outlets daisy-chained (two wet bar outlets and two entertainment system outlets). The first outlet in the chain is GFCI and will trip when I turn power OFF to either of the fans. It does not trip when I power ON the fan. I think what is happening is that at the moment the fan is powered off, the fan still spins for a while and produces back EMF. Perhaps this is what is tripping the GFCI? If this was a DC fan, the fix would be simple: a 1N4001 diode across the fan terminals. I don't know what the fix would be for AC fans. I'm tempted to try a different GFCI from a different manufacture to see if that changes things as suggested by vtboy51. I need to get this fixed as I will have an entertainment system and a Megatouch game plugged into those outlets downstream of the GFCI.


----------



## secutanudu (Mar 15, 2009)

What manufacturer gfci do you have? Mine is a Leviton 15A from home depot. I have some in the house from lowe's - I think cooper. I'll try swapping them.

Also - I think it only trips when flipping the switch slowly.

Maybe a different switch - like a fancy timer switch - would help.


----------



## Wildie (Jul 23, 2008)

Hmmm! I'll recount my experience!

The single incandescent in the laundry area didn't provide enough light. So, I bought a T8 single lamp fixture (with a pull chain switch at HD.
I plugged it into the GFCI in the laundry area and all was fine for about 2 years!
I have been rearranging the location of the laundry receptacles and I hooked up the new wire, in the same manner as it had been connected before.
When I pressed the TEST button the GFCI tripped, but the light stayed on?????
Taking the receptacle apart, I found that the LINE wire were connected to the LOAD terminals.
Connecting them properly, everything seemed to function as required.
However, from time to time, when turning OFF the fixture with its pull chain switch, the GFCI trips!
I have a dehumidifier plugged into the same outlet, its auto start and stop, and it is not a problem.
The GFCI never trips until the flourescent fixture is turned off.
I have yet to open up the fixture, but it does have an electronic ballast (Chinese ?) so I'm wondering if this gives a kick that trips the GFCI!


----------



## Yoyizit (Jul 11, 2008)

*I plugged it into the GFCI in the laundry area and all was fine for about 2 years!*

So it must have been right.

*However, from time to time, when turning OFF the fixture with its pull chain switch, the GFCI trips!*

So the leakage current is at or slightly below the GFCI tripping threshold?

*I have a dehumidifier plugged into the same outlet, its auto start and stop, and it is not a problem.*

Could be the cumulative effect of the fixture and this heavy load.

*The GFCI never trips until the flourescent fixture is turned off.
I have yet to open up the fixture, but it does have an electronic ballast (Chinese ?) so I'm wondering if this gives a kick that trips the GFCI!*

e = -L(di/dt); you should get a huge voltage spike when you interrupt the current in a circuit containing inductance. 
Possibly this could be fixed by putting a 400v MOV on the fixture.


----------



## Wildie (Jul 23, 2008)

Yoyizit said:


> *I plugged it into the GFCI in the laundry area and all was fine for about 2 years!*
> 
> So it must have been right.
> 
> ...


 It does seem to be an inductance back EMF, that is the root cause! I plan to have a look inside this fixture, but its way down the list! [wife is ill and I'm chief cook and bottle washer, at the moment]


----------



## Yoyizit (Jul 11, 2008)

You can check the leakage current in the ground lead if you'd like. You just need a meter and a small incand. lamp.
If it's near the trip threshold this could be the problem. 5 mA is the max, but most GFCIs trip at less than this value.


----------



## Chucky Jesus (Jul 21, 2009)

I checked mine and it was a Leviton "Pro" 20A GFCI. I have this on a 15A breaker from the panel and 14/2 romex. I will find a properly sized (15A) GFCI from a non-Leviton manufacturer this weekend and replace it....


----------



## secutanudu (Mar 15, 2009)

You can't legally have a 20A outlet on a 15A breaker anyway, so good idea 

I'll probably swap my GFCI with a different brand at some point. I'll post results when i do.


----------



## Wildie (Jul 23, 2008)

Yoyizit said:


> You can check the leakage current in the ground lead if you'd like. You just need a meter and a small incand. lamp.
> If it's near the trip threshold this could be the problem. 5 mA is the max, but most GFCIs trip at less than this value.


 Something odd happened with this GFCI today! I was hammering in Romex staples near where the GFCI and it tripped from the vibrations. 
So now, I'm wondering if the GFCI is defective? 
Are these usually sensitive to any sort of physical vibration etc?


----------



## Yoyizit (Jul 11, 2008)

Wildie said:


> Something odd happened with this GFCI today! I was hammering in Romex staples near where the GFCI and it tripped from the vibrations.
> So now, I'm wondering if the GFCI is defective?
> Are these usually sensitive to any sort of physical vibration etc?


I suppose they shock-test these things to some level of G force. Dropping a wrist watch on a hard floor is 5000 Gs, I think.

Does it reset?


----------



## Wildie (Jul 23, 2008)

Yoyizit said:


> I suppose they shock-test these things to some level of G force. Dropping a wrist watch on a hard floor is 5000 Gs, I think.
> 
> Does it reset?


 Oh yes! And test's OK as well! :huh:


----------



## Yoyizit (Jul 11, 2008)

Wildie said:


> Oh yes! And test's OK as well! :huh:


I'm inclined to think it shouldn't have done it.

You can test it independently for a dollar or so in parts by running resistors from the hot outlet slot to ground. 
If you use 120v in Canada
for 1 mA use a 120k 1/4w resistor
for 2 mA use 62k 1/2w
3, parallel these two resistors.
4mA, use 30k 1w
5mA, parallel #1 and #4


----------



## Chucky Jesus (Jul 21, 2009)

I finally got around to picking up a 15A GFCI to replace the 20A. Unfortunatley, the store only had Levitron. So, the box says 15A and moulded into the plastic is 15A. However, there is a white sticker on it that says 20A. WTF?  I examined the 20A GFCI I just removed. Same thing, 15A moulded into the plastic, but with a similar white 20A sticker. The only differences between these two GFCI's is that the new one is brown, the old one is white (brown goes better with the brown glass tiled backsplash); the new one is "Tamper Resistant" and the old one is not. I am going to go ahead and install the brown one this weekend and see if simply having a different unit from a different lot will produce different (hopefully favorable) results....


----------



## secutanudu (Mar 15, 2009)

A 20A outlet has a "T" shaped slot on it. It allows you to plug a 20A device (which also has a "T" shaped plug) into it. 

A 15-Amp outlet is rated for 20A "passthrough", meaning you can put it on a 20A circuit but not plug a 20A device into it. If your old outlet didn't have a T slot, then it was a 15A outlet.


----------



## Chucky Jesus (Jul 21, 2009)

Bingo secutanudu!

Yep, both GFCI's I have do not have a T-shaped slot. 

I installed the new, brown GFCI and apparently it has a different trip point. Now I can turn on and off my upstream fans to the GFCI at will and it does not trip. :thumbup:

I tossed the white one in the trash.


----------



## secutanudu (Mar 15, 2009)

So - the new one you bought was Leviton? That's the brand I am having issues with...


----------



## Chucky Jesus (Jul 21, 2009)

Yeah. Both are Levitron. I really didn't have a choice. It's all the hardware store had. I rolled the dice hoping that a different lot from the same manufacture would produce different results. I guess I hit the GFCI lottery. :laughing: If it does it again, I will put more effort into looking for non-Levitron. Perhaps buy online.


----------



## secutanudu (Mar 15, 2009)

I know Lowe's sells Cooper - I guess I can try them.


----------



## Chucky Jesus (Jul 21, 2009)

Thanks. I'll remember that if the Levitron gets flakey again. Let us know if the Cooper works for you.


----------



## tdeg807 (May 29, 2010)

*Must be Levitons...*



secutanudu said:


> What manufacturer gfci do you have? Mine is a Leviton 15A from home depot. I have some in the house from lowe's - I think cooper. I'll try swapping them.
> 
> Also - I think it only trips when flipping the switch slowly.
> 
> Maybe a different switch - like a fancy timer switch - would help.


I am having the same issue in my daughter's bedroom with a ceiling fan. I replaced a non-grounded outlet with a Leviton SnapLock (might not be the right name, threw out the package). The fan is on the load side of the circuit from the GFCI. When the fan is turned *off* the GFCI trips. I've replaced the GFCI with another Leviton and same issue. Moved the old GFCI to the bathroom and had no issues with it. I also replaced the switch for the fan and this also made no difference.

Its not consistent either. It seems to not trip if the lights in the fan are turned on when I turn off the switch. This is leading me to believe when I turn of the switch with the fan on, the fan is essentially becoming a generator and putting a voltage on the wire to the switch which the GFCI is somehow picking up and tripping. With the lights on, the voltage is dissipated.

(first post on the forum, so sorry if its long... been searching this forum for a while looking for a couple of issues I have. This is one of them so if the Cooper idea works, I know where I can get one).


----------



## Yoyizit (Jul 11, 2008)

tdeg807 said:


> When the fan is turned *off* the GFCI trips.
> It seems to not trip if the lights in the fan are turned on when I turn off the switch.


GFCIs are supposed to trip when they sense a current difference. The trip time depends on the current, according to T = (20 / I)^1.43, so 20 mA of leakage current will trip in less than one second and 5 mA will trip in less than 7 seconds.

Anyway, this current difference is a 'differential mode' signal.
When the current in both lines changes equally, like when you turn something on or off, this is a 'common mode' signal and is supposed to be rejected by the GFCI. The higher the 'common mode rejection ratio' the better the device does its job.

The current change in both lines is larger when there are no other loads on the GFCI, so if you have a steady load of a few amps the fan turning off won't make that much of a difference.

I was unable to find GFCI patents relating to methods of getting around these spurious responses to large, abrupt, common mode signals. If you can find some, like by Googling 
GFCI 
the assignee company is a probably a good place from which to buy one of these.

Good addt'l search keywords would be 
abrupt
change
current
nuisance
false
rejection
large
load
differential

BTW, if you have a good idea, others will steal it. It's the way of the world!
http://ewweb.com/mag/electric_leviton_wins_gfci/


----------



## Jim Port (Sep 21, 2007)

Yoyizit said:


> GFCIs are supposed to trip when they sense a current difference. The trip time depends on the current, according to T = (20 / I)^1.43, so 20 mA of leakage current will trip in less than one second and 5 mA will trip in less than 7 seconds.


You might want to compare your "facts" vs the published specs provided by Hubbell. Hubbell state the response times at .025 seconds. I guess you could say that .025 seconds is less than 7 seconds, but I wouldn't want to depend on your "stats". Are you even aware of the amount of damage that could be done if UL allowed trip levels like you allege?

Here is the link, check the bottom of page 3.

https://www.hubbellnet.com/max_htm/PDF_Literature_Library/h4511.pdf


----------



## PaliBob (Jun 11, 2008)

*--Trip Times--*

Yoyizit is correct about GFCI's not tripping instaneously.
While GFCI's will typically trip in 25 ms or so at fault currents exceeding 20 to 30mA, they are permitted by UL to take several seconds to trip at fault currents in the 6mA range.


Source: ​http://ecmweb.com/mag/electric_think_gfci/
Ref: 2nd paragraph after Why GFCI's

The Hubbell Spec qualifies their 25mS number by adding _Nominal_


----------



## Knucklez (Oct 21, 2007)

this is an interesting topic Yoyizit. where dose 1.43 come from? at first i thought you meant peak current, which is 1.41, but you seem firm on 1.43.

as for minding against spurious faults at turn on, what i think is happening is the large inrush of motor in the fan (5-7x nominal) is creating a high di/dt (rate of change of current) which is parasitically coupling to ground. since some of the current is going to ground, instead of returning to the source, it triggers the GFCI as a differential fault. if this is the problem, then solution is to buy a fan with an advanced motor drive inside (variable speed) and hope it comes with electronic protection against inrush. or maybe you could just coil up some of the source wire to create an inductance.. what do you think?

as for common mode trips, easiest solution here is to get some high-mue torroidal cores and just run the power wires through it. the black & the white through the donought center of the core. the common mode flux will circulate in the core.

Knucklez


----------



## Yoyizit (Jul 11, 2008)

Knucklez said:


> where dose 1.43 come from?


UL 943, which probably used Dalziel's research. This formula is also in the online manual for Ideal's house wiring tester/analyzer, 61-165 or 65-165. It plots out as a straight line on log-log paper and I guess they used a best fit routine to match the data. The curve is a maximum.

Like a circuit breaker's trip curve is designed to prevent wire from reaching excessive temperatures this curve is designed to protect most people from injury or death. As I recall, Dalziel had trouble getting reliable data on kids because instead of reporting their discomfort level they would cry.

I guess a variable speed motor may help, if the speed control doesn't cause additional transients.


----------

