I’ve got a tripping problem (and no, not like Summer of Love circa 1970’s type trippin). When I turn off my overhead vent fan, it will occasionally trip the GFCI.
My 1960 vintage Calif. house has an ancient kitchen ceiling vent fan. When I rewired my kitchen some months ago, rather than tear down the whole kitchen wall and part of the ceiling to replace the old 2 wire, no ground, 12 gauge wire, I just hooked it onto a switch in a box that was downstream from a GFCI.
I use the fan only occasionally and it went probably six months or more with no problem in evidence. Yesterday when I turned the fan off, it tripped the GFCI. I then turned the the fan off and on a dozen times and it tripped it once but not the next dozen.
My WAG is that the motor windings act enough like a coil to send a small current down the wire as the magnetic field collapses when the power is switched off. If that is the case, a possible guess is to put a capacitor between one of the fan circuit wires and a ground somewhere between the fan and the GFCI to try and shunt the current spike to ground, but I have no idea of what size capacitor to try and even less of an idea how the code regards sticking capacitors between a circuit and ground in a box.
Any suggestions that don’t involve again remodeling my kitchen would be appreciated.
Replies
Replace the GFCI with a new one that alleges to stop nuisance trips.
Adding the cap will just make the problem worse. It's capacitance to ground that's causing the problem.
I'd start by trying a different model of GFCI.
Take the wires (Fan) off the Load side of the GFI and attached it to the Line side. The GFCI plug will still work and the Fan will not be protected by the GFIC. If there are other plugs that need to be protected, then change those to GFIC plugs.
Sungod - that would be a good suggestion, except at this point it would require the tearing out of about ten feet of newly installed kitchen drywall. Not exactly the easy solution I had hoped for...Dan - how would it be capacitive coupling to ground on a fan motor that is not only ungrounded but is buried in an insulating panel with no contact with anything that conducts? If it were a startup surge, there are a number of circuit elements that could be used to "soft start" the circuit. Not sure they would as well for a "soft off". Dam Inspector - This is a standard Lutron GFCI purchased in bulk from my local electrical supply. I have not seen any GFCIs that make any claims against false tripping. Any brand names? The problem with replacing with a different brand is that all the outlets in the kitchen are "almond" color and one of a different color would definitely stand out.
Maybe I didn't read things right, but No drywall has to be touched. You just rearrange the wires directly behind the culprit GFIC.
The load side of the GFCI feeds through another box into yet another box some ten feet distant. It is into this last box that the switch for the fan is connected to the down stream side of the GFCI.
So keep the old GFIC in place, energize the box 10' away from the line side of the old GFIC.
At the box 10' away add another new GFIC with the fan energized by the line side of the GFIC, not the Load side.
Each GFIC will only protect its own plug not any other plug or fan.
OK, let's see, I just need to install two more GFCIs in place of the downstream outlets. I guess that might actually work if I can actually squeeze them in.
Edited 6/13/2009 8:32 pm ET by CaseyR
Something along these lines would be worth trying.
http://www.leviton.com/OA_HTML/ibeCCtpItmDspRte.jsp?sitex=10026:22372:US&item=280741
ThanksI think that all GFCIs are supposed to trip at the same level. However, the tolerance of plus or minus 1ma may mean that some GFCIs from the same brand are more liable to trip. I have a couple of spare GFCIs, so I may try swapping them in to see what happens before I try a diffeent brand to see if it is any different.
Some cheap GFCIs are susceptible to high frequency noise, such as a slight arc when a switch is opened on an inductive load. The better ones will state that they are resistant to nuisance trips. A nuisance trip is not a ground fault, it is a false trip due to electrical noise.A Hubbel brand is probably the best.
There's capacitance in the wiring, and in the motor itself.
As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz
You have an old fan ... and you think the problem is with the GFCI?
Insulation loses it's ability as it ages. I suspect that the fan motor would fail a 'megger' test - indicating that the insulation in the motor windings is about shot. If the fan had a good ground path, it would likely trip the GFCI every tine - and maybe trip the breaker as well.
Megger the fan, and the wires feeding it.
Motors should never be put on a GFCI circuit.
Jeff
Jeff,"Motors should never be put on a GFCI circuit."Why?Steve
I was wondering the same thing. After all, hair dryers have motors.
Motors do have a "tendency" to trip GFCIs, since they cause transients, especially when starting/stopping. But most modern GFCIs can handle reasonably sound motors up to 1/4HP or so without tripping. And since motors are more likely to develop internal shorts to ground than most other devices, a GFCI on a motor is a good idea.
As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz
This "motors are going to trip GFCIs" thing is simply ridiculous.
If that was true you couldn't sell electric lawn tools, power tools likely to be used in garages, pool/spa pumps, boat lifts or any number of things we use every day. I have a, refrigerator, a PC, washing machine, pool and spa pumps, a boat lift and a garage full of power tools that work just fine on GFCI. If your motor is tripping a GFCI you have a bad appliance. That is particularly true of washing machines and fridges.
I've had motors (admittedly cheap ones) that trip GFIs. I don't think there were any safety issues, but it is annoying.I'd be inclined to move this motor off the GFI.Scott.
> If your motor is tripping a GFCI you have a bad appliance.Not true. Motors do create significant start/stop transients, and AC/DC motors can create a lot of run hash as well. These transients can "fool" GFCIs. But both the motors and the GFCIs have been modified over the past 30 years to where such problems are far less likely than originally.If a motor is tripping a GFCI my first suspicion would be the GFCI.
As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz
Well, I'm not one to challenge a man's religious beliefs!
There is no denying that the GFCI has come a long way, from qhat it was when first introduced in the 70's. In the decades since, all manner of wonderfully elaborate theories were advanced to explian various GFCI "problems." Indeed, several years back (was it 2003?) the UL standard was revised to create some transients, that the GFCI had to ignore in order to pass.
Less obvious is that, over the same time period, appliance manufacturers have greatly improved their products.
Simply put, NO modern appliance ... be it doorbell, a motor, a refrigerator, etc., should trip a GFCI unless something is wrong.
Left unaddressed are older appliances, which either have poor design issues, or are simply worn out.
It's been a very long time since I had to deal with a 'nusaince tripping' GFCI. When the UL standard was changed, there was a bad run of the new ones .... but that was the exception. Like a tripping circuit breaker, the GFCI invaraibly trips for a good reason. When I do encounter a 'broken' GFCI, it has almost always been subjected to many trip/reset cycles and high current draw.
New wire -> new GFCI -> old wire -> old fan. Gee, I wonder where the problem is?
Thing is, if the unit is only tripping when the fan is turned on or off it's highly unlikely that the problem is due to resistive leakage. Could be an RFI bypass cap on the motor or some such, but unlikely to be an actual failure.
As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz
Really? Combine knob & tube wiring and a wood frame ... just where is leackage current likely to go? With an unreliable path to ground, the problem will be intermittent. That's why I suggested a megger test.
Or, we can continue to replace items that just passed through the manufacturer's quality control department.
Hey, the GFCI is bad. The OP says there is no ground wire, so there is no known real path to ground. Which only leaves me with one conclusion. A bad (or more correctly, false tripping) GFCI. The GFCI only compares the current on the hot to the current on the neutral, if they match, no fault is present. Some GFCI's will trip with rf noise or spikes on the line, which is called a nuisance trip.OH, by the way there is no knob and tube wiring mentioned.
I was pretty plain in both my explanation, as well as my wat to test the system.
Anyone who got lost following the post .... or who thinks you need a ground wire for a GFCI to work ... really needs to leave electricity alone.
I suppose it's also possible that the fault is with the switch. We can add that to the wire feeding the fan, and the fan itself, as possible problems.
As for others' comments: if you have a motor that keeps tripping a GFCI ... you have a problem with the motor, not the GFCI. Save all the techno-babble for Jeopardy.
Apparently your electrical understanding of GFCI's and reading comprehension is lacking. No you don't need a ground for one to work, and I didn't say you do. You do need the same current in both hot and neutral or there is a fault. If the load is unbalanced the GFCI will trip (say from current from the hot leaking to ground). It's just that simple.Since there is no apparent return path to ground, the GFCI is tripping on a nuisance fault.
<<<Anyone who got lost following the post .... or who thinks you need a ground wire for a GFCI to work ... really needs to leave electricity alone.>>>That seems to apply to you as well. I don't know what you do, but I worked with "electricity" and electronics for the last 28 years.
My wife's hair dryer trips a standard Leviton GFCI at the bathroom sink all the time.
From my experience they tend to be overly-affected by motors - maybe due to the extent of current leakage at lock-rotor amperage (??) - not sure.
Where the code requires it - well hey you have no choice - but rots o ruck. I've seen a flooded basement from a sump pump having tripped a GFCI and no one caught it.
Jeff
Our hairdryer used to trip the GFCI also. It started out with an occasional trip, but eventually it would trip every time the hairdryer was plugged in or unplugged... even with the motor off.
I replaced the GFCI and it's been trouble free ever since. of course, this may or may not apply to your GFCI.
I think whirpool tubs HAVE to be on a GFCI ??
What about where the code very explicitly requires GFCI's on motors. And while I think that many GFCI requirements are overblown that is not one of them..
William the Geezer, the sequel to Billy the Kid - Shoe
Most things plugged into gfci outlets in kitchens and baths have a motor.