Best GFCI to avoid nuissance trips for bath fan?

[JHZR2]

I would have liked to continue the following thread:

http://forums.mikeholt.com/showthread.php?t=161445

but it's closed down. Essentially I'm having the same issue - inductive kickback of a bath fan with enough inductance in the circuit to get a high L di/dt and force a voltage with nowhere to go, which I guess creates a minor current that will occasionally trip the GFCI. I had an old (70s or 80s???) GFCI that fed a bath fan with a switch loop. It nuissance tripped maybe twice over many years so I thought to replace it (the face was cracked too)... Put in a Leviton from HD.

Since then, the bath fan has been tripping more and more often,,especially over the last six months or so.

Recently we decided we wanted a bath fan with a light, so we got a nice, silent, Panasonic one. Really great. I replaced the switch loop and the switch too, and now its tripping more and more - like almost every time we actually use it for a while for showers. So no change with new vs old fan, switch, and wiring... Getting worse. So must be the GFCI.

Some others showed vendor issues here:

http://forums.mikeholt.com/showthread.php?t=98497

So, what brand, or perhaps model within a brand even, would have a better circuit board and design, less prone to these nuisances?

thanks!

 

[mbrooke]

I would first check to make sure there isnt a ground fault someplace. Newer GFCIs rarely trip without reason.

 

[JHZR2]

I would first check to make sure there isnt a ground fault someplace. Newer GFCIs rarely trip without reason.

Fluke 77 indicates no issue in terms of continuity with ground conductor.

Replacement of fan, switch and wiring has not changed the situation.

Where else could the issue lie?

 

[mbrooke]

Fluke 77 indicates no issue in terms of continuity with ground conductor.

Replacement of fan, switch and wiring has not changed the situation.

Where else could the issue lie?

I would megger. Inspect all jboxes in the circuit after the GFCI. I doubt its tripping on anything other then a ground fault.

 

[ptonsparky]

As in the other post, when does it trip? While in operation or at stop?

We were using a 6-lamp t5 fixture for temp lighting on a project. It would trip any of the Levton GFCIs we tried, but the Coopers held. ??

Our own exhaust fan in the utility room would trip a GFCI we had in that room when the fan was switched off. Totally different circuits.

These are the only two instances I can remember that were unusual tripping of GFCIs. Barring lightning and outright failure of the unit.

 

[JHZR2]

The GFCI trips ONLY EVER at switch-off. Never had any issues whatsoever other than at switch off time.

There re are no junction boxes - it is a straight run of 14/2 from the load side of the GFCI to the fan box. And the new fan was rewired with new conductors, so there's not some oddity in the situation that I can grasp.

ill have to access a merger to see. I'm just not grasping how it could be the case.

 

[mgookin]

.

 

[gar]

150831-0920 EDT

JHZR2:

I have been able to trip a Leviton GFCI with a high dv/dt signal, such as switching an inductive load.

I believe the cause is the Levition circuit board layout. There is a moderately long trace, about a half inch, leading to the gate of the SCR that operates the trip coil. Capacitive coupling from a high dv/dt signal from adjacent circuitry could trigger the SCR.

Try ptonsparky's suggestion of a Cooper. I have not looked at the internal layout of a Cooper and don't know how this would differ relative to the Leviton..

.

 

[ptonsparky]

In the case of my bath fan, it tripped the Cooper GFCI as well.

I used an RCS1A-6 from R-K Electronics at the fan motor to stop the tripping. Hot to neutral. Hasn't tripped since.

 

[Tony S]

As suggested in #4 use a Megger, a Fluke 77 can’t check for insulation breakdown in the circuit. Disconnect the fan run on timer first otherwise you’ll fry it.

The inductive spike on disconnection can be several times the line voltage, enough to find any weak points in insulation. I’ve seen it do some spectacular damage taking out 630A fuses.

 

[Curious nerd]

I don't know if this is right

I don't know if this is right

There's a belief out there that if the homeowner has a surge-protected power strip somewhere on the same circuit, it can cause GFCI trips. The idea is motor goes off, inductive spike happens, it's higher than the surge protector's design point, the surge protector sees an L-G overvoltage and shorts it out, and then there's a ground fault.

I've had a miracle cure installing a Pass&Seymour GFCI in a case with exactly the same symptoms as the OP's.

 

[Dennis Alwon]

May I ask if the gfci is necessary? If the fan is not over the shower then no gfci is needed. Btw , my favorite receptacles are Pass and seymour

 

[ptonsparky]

There's a belief out there that if the homeowner has a surge-protected power strip somewhere on the same circuit, it can cause GFCI trips. The idea is motor goes off, inductive spike happens, it's higher than the surge protector's design point, the surge protector sees an L-G overvoltage and shorts it out, and then there's a ground fault.

I've had a miracle cure installing a Pass&Seymour GFCI in a case with exactly the same symptoms as the OP's.

FWIW, we had a customers AFCI that would trip with those cheap surge strips. Throw the POSs out.

 

[geoffspanky]

You need to find out from the manufacturer if the GFCI is suitable for an inductive load. Switch mode power supplies also cause problems for some GFCI's due to DC current.
GFCI's (Australia) are available in three types. AC, A and S. In practice if you have a standard AC type that is nuisance tripping you would replace it with an A type. The S type or selective GFCI's are for more demanding applications where voltage spikes and DC currents are present.


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[ramsy]

GFCI's (Australia) are available in three types. AC, A and S. In practice if you have a standard AC type that is nuisance tripping you would replace it with an A type. The S type or selective GFCI's are for more demanding applications where voltage spikes and DC currents are present.

Have a link to OEM products?

 

[geoffspanky]

http://www.nhp.com.au/files/editor_upload/file/product-tools/dsrcd.pdf


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[hbiss]

FWIW, we had a customers AFCI that would trip with those cheap surge strips. Throw the POSs out.

I can attest to that first hand. My wife has one of those "receptacle expander"/surge protectors plugged into our bathroom GFCI because she has all kinds of junk plugged in. It trips all the time for no apparent reason.

-Hal

 

[JHZR2]

You need to find out from the manufacturer if the GFCI is suitable for an inductive load. Switch mode power supplies also cause problems for some GFCI's due to DC current.
GFCI's (Australia) are available in three types. AC, A and S. In practice if you have a standard AC type that is nuisance tripping you would replace it with an A type. The S type or selective GFCI's are for more demanding applications where voltage spikes and DC currents are present.


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Very interesting, not sure I've seen such ratings here...

 

[JHZR2]

In the case of my bath fan, it tripped the Cooper GFCI as well.

I used an RCS1A-6 from R-K Electronics at the fan motor to stop the tripping. Hot to neutral. Hasn't tripped since.

How ow does that work? Is it effectively just a 220 ohm constant short from hot to neutral? Does it dissipate energy at all times?

i assume it was just wire nutted in at the fan junction box?

 

[Dennis Alwon]

I used an RCS1A-6 from R-K Electronics at the fan motor to stop the tripping. Hot to neutral. Hasn't tripped since.

So does that make the install compliant?