Leviton GFCI nuisance tripping and circuit analysis

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tersh

Senior Member
Location
new york
I know many electricians and vendors, engineers encounter nuisance tripping with the Leviton GFCI. After all these years. Is there finally a theory why? If not. Let's figure it out and analyze the circuit.

First. This is a Waterpik mouth spray shaded-pole motor. See youtube video how it works at

https://www.youtube.com/watch?v=PmNcRsxSovs

XeOzCF.jpg



Even if the plug is 2-prong (without any grounding and it's put on glass surface). The Waterpik motor can consistently trip the Fairchild chipset (I tested 4 units and same results). This is used in the Leviton. It doesn't trip on other brands of GFCI such as the Siemens GFCI. It's even when the motor was isolated and not wet (even if rotor removed). The trips occur either during startup or turning off (50% of the time). Not when it's already on.

For other load that trips sometimes, it's difficult to figure it out. But not this when it can do it consistently so we can do experiments that can figure out the technical reasons.

This is the circuit diagram of the GFCI also used by Leviton.

q6aYfG.jpg



http://datasheet.elcodis.com/pdf2/81/73/817329/rv4141a.pdf

See the Leviton teardown at https://www.powerelectronictips.com/teardown-leviton-ground-fault-circuit-interrupter/

The second sense coil works only if there is a ground, right? So what part do you think is tripping the circuit? There are many theories elsewhere. Some say the inductive load could have the magnetic field still not going to zero in one wire producing temporary imbalance in the sense coil, but why doesn't it trip other brands of GFCIs (such as the Siemens)?

https://www.justanswer.com/electrical/2g0be-gfci-outlet-trips-even-when-clear.html

Why is your theory? Don't suggest wiring problem because it is not that.

This is important for electricians, vendors, engineers and even users to know the reasons so can share the knowledge and avoid headaches and inconvenience.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
190106-2516 EST

tersh:

I have expressed an opinion on this before.

Look at the board layout. There is a long trace from where C3 is located to the SCR gate. I suspect that transient capacitive coupling to the SCR gate is the cause.

Try putting C3 directly at the SCR gate, and a 100 ohm carbon comp resistor in place of the trace. This creates a low pass filter at the gate input and also reduces the capacitive coupling to the gate.

I think that inductive kick at either turn on or off is the source of the transient.

.
 

tersh

Senior Member
Location
new york
190106-2516 EST

tersh:

I have expressed an opinion on this before.

Look at the board layout. There is a long trace from where C3 is located to the SCR gate. I suspect that transient capacitive coupling to the SCR gate is the cause.

Try putting C3 directly at the SCR gate, and a 100 ohm carbon comp resistor in place of the trace. This creates a low pass filter at the gate input and also reduces the capacitive coupling to the gate.

I think that inductive kick at either turn on or off is the source of the transient.

.


But even if the motor is 3 meters away from the GFCI outlet. It still triggers it. What is the range of the capacitve coupling. Maybe by using long extension, one can test if capacitive coupling is the cause?

Do you find it present in all Leviton models (with and without the 2015 auto-monitoring self-test?) Why don't other brands have the same issue?
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
So what part do you think is tripping the circuit?
If you mean the grounded-neutral: Bypassing RG is the only thing I can see.

If you mean the nuisance tripping: I'm guessing the appliance switch arcing.

I have no idea why it's sensing arcing, though.
 
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kwired

Electron manager
Location
NE Nebraska
I don't generally use Leviton GFCI's so don't know how prone they are to such trips.

I do agree that it is likely inductive kickback that is causing the problem if you know there is no ground faults going on, probably happens either when turning on or turning off the appliance?
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
190107-1719 EST

tersh:

I am talking about capacitive coupling within the GFCI device. Thus, the length of wire from the GFCI to the load is not a big factor other than how that affects the voltage transient level when it gets to the GFCI device. The suggestion I was making relative to the GFCI circuit board is to put the shunt capacitor directly at the gate-cathode of the SCR instead of about 1" away. And the series resistor ln combination with the shunt capacitor to the gate is to reduce transient voltage at the gate.

.
 

tersh

Senior Member
Location
new york
190107-1719 EST

tersh:

I am talking about capacitive coupling within the GFCI device. Thus, the length of wire from the GFCI to the load is not a big factor other than how that affects the voltage transient level when it gets to the GFCI device. The suggestion I was making relative to the GFCI circuit board is to put the shunt capacitor directly at the gate-cathode of the SCR instead of about 1" away. And the series resistor ln combination with the shunt capacitor to the gate is to reduce transient voltage at the gate.

.

Have you tried doing it to a Leviton GFCI circuit board itself? Why didn't you?

Also why is only certain motors affected, like shaded-pole motor in Waterpik but not washing machine motors?

Does a refrigerator have any motor that can do that? When I used the Fairchild based GFCI similar to Leviton, my refrigerator trips the GFCI once or twice a day. But not the Siemens GFCI (which I'm still testing and it's been a day without trip already). If the fridge won't trip the Siemens GFCI for more days then it solves a mystery why seemingly new fridge can trip GFCIs. It's not the fridge fault but the GFCIs.
Debate rages whether the inductor in fridge can lose the current. Since it doesn't, many suggest to replace the fridge. I didn't read any suggestion it is the GFCI fault.
 

mopowr steve

Senior Member
Location
NW Ohio
Occupation
Electrical contractor
As far as issues with refrigerators,

The circulation fan in the freezer section behind the back panel is a shaded pole just like the ones used in exhaust fans. So one could expect the same results at turn on and shut off. Unless the problem had anything to do with defrost element issues or erratic compressor issues.

My experience with the Leviton GFCI receptacle was primarily when the shaded pole motor was shut off. Because often times a customer would leave the bathroom, turn fan off, and upon returning the GFCI would be in the tripped position.
 

tersh

Senior Member
Location
new york
As far as issues with refrigerators,

The circulation fan in the freezer section behind the back panel is a shaded pole just like the ones used in exhaust fans. So one could expect the same results at turn on and shut off. Unless the problem had anything to do with defrost element issues or erratic compressor issues.

My experience with the Leviton GFCI receptacle was primarily when the shaded pole motor was shut off. Because often times a customer would leave the bathroom, turn fan off, and upon returning the GFCI would be in the tripped position.

How often does the circulation fan turn on in a refrigerator?

It's good I tried the Waterpik and try another GFCI for the fridge. I bought an expensive 500va isolation transformer just to isolate the fridge thinking that it can trip all GFCI. No one told me the fridge can only trip on Leviton GFCI. It could have saved me $200 on the isolation transformer.
 

mopowr steve

Senior Member
Location
NW Ohio
Occupation
Electrical contractor
If memory serves me right, I believe it runs at minimum whenever the compressor is running, if it runs constantly it may shut off durring defrost cycle.
 

tersh

Senior Member
Location
new york
As far as issues with refrigerators,

The circulation fan in the freezer section behind the back panel is a shaded pole just like the ones used in exhaust fans. So one could expect the same results at turn on and shut off. Unless the problem had anything to do with defrost element issues or erratic compressor issues.

My experience with the Leviton GFCI receptacle was primarily when the shaded pole motor was shut off. Because often times a customer would leave the bathroom, turn fan off, and upon returning the GFCI would be in the tripped position.

Does this occur constantly when the shaded pole motor was shut off? My experience is once for every two tries (or more) or 50% (or 75%) of the time. How about your experiences?
 

ELA

Senior Member
Occupation
Electrical Test Engineer
Electric Fast Transient Testing

Electric Fast Transient Testing

Historically GFCIs have nuisance tripped due to the Electric Fast Transient generated when fan motors were shut off ( inductive kick ).

Many electronic devices are susceptible to failure when exposed to repeatable Electric Fast Transients - at varying amplitude and repetition rates - as set at the Test Generator.

I used to have access to a number of EMC test equipments including an EFT Generator.
No problem screwing up a lot of electronics when exposed at certain rates and amplitudes.

European markets require equipment to pass EMC testing, including EFT testing, in order to be CE marked. We performed pre-compliance EMC testing.

The EFT generator can force a GFCI to nuisance trip at a very high repeatably rate as opposed to the random EFT transient generated by a motor turn off.
 

tersh

Senior Member
Location
new york
Historically GFCIs have nuisance tripped due to the Electric Fast Transient generated when fan motors were shut off ( inductive kick ).

Many electronic devices are susceptible to failure when exposed to repeatable Electric Fast Transients - at varying amplitude and repetition rates - as set at the Test Generator.

I used to have access to a number of EMC test equipments including an EFT Generator.
No problem screwing up a lot of electronics when exposed at certain rates and amplitudes.

European markets require equipment to pass EMC testing, including EFT testing, in order to be CE marked. We performed pre-compliance EMC testing.

The EFT generator can force a GFCI to nuisance trip at a very high repeatably rate as opposed to the random EFT transient generated by a motor turn off.

My Fairchild based GFCI (used by Leviton) can consistently trip at almost 80% high repeatably rate. Not only during off but during on. Does inductive kick involved turning on also?

My GFCI outlet is 240v line to line. I guess the inductive kick of 240v is similar to one of 120v? Is inductive kick sensitive to voltage?

In the US. You can simply replace it with another brand. But in my Philippines. Since there is only one 240v brand of GFCI receptacle in the entire world available. Then no other choices to choose. The circuit was exactly like that shown in the original message but only voltage changed. The Fairchild chipset can accept both 120v and 240v. http://datasheet.elcodis.com/pdf2/81/73/817329/rv4141a.pdf
 

junkhound

Senior Member
Location
Renton, WA
Occupation
EE, power electronics specialty
my bet would be that the turn on or turn off transients occasionally series resonate thru the 1:200 CT secondary with C1 to fake the input of the chip into seeing an output of the first CT. The SCR input has a 4.7k to ground inside the chip (plus theexternal gate cap), so it would take a big transient to directly trip the SCR.

PS: side experiment for those with the time /g Regular switch (not a snap action switch) being opened and closed at fast and slow rates- which will trip the gfci? Also try with snap action switch or electronic switch, results should be consistent (either nearly always trip or not trip)
 
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tersh

Senior Member
Location
new york
my bet would be that the turn on or turn off transients occasionally series resonate thru the 1:200 CT secondary with C1 to fake the input of the chip into seeing an output of the first CT. The SCR input has a 4.7k to ground inside the chip (plus theexternal gate cap), so it would take a big transient to directly trip the SCR.

PS: side experiment for those with the time /g Regular switch (not a snap action switch) being opened and closed at fast and slow rates- which will trip the gfci? Also try with snap action switch or electronic switch, results should be consistent (either nearly always trip or not trip)

Here is another clue. If I connect the shaded pole motor to a Siemens GCFI breaker (which doesn't trip) in series to the Leviton based GFCI. Both won't trip.

How come putting the Siemens GFCI breaker between the shaded pole motor and the Leviton based GFCI outlet won't trip the latter?

If only the shaded pole motor and Leviton based GFCI is connected, the latter trips 80% or 90% of the time or so consistently (like 4 trips for every 5 switchings).
 

rlundsrud

Senior Member
Location
chicago, il, USA
Here is another clue. If I connect the shaded pole motor to a Siemens GCFI breaker (which doesn't trip) in series to the Leviton based GFCI. Both won't trip.

How come putting the Siemens GFCI breaker between the shaded pole motor and the Leviton based GFCI outlet won't trip the latter?

If only the shaded pole motor and Leviton based GFCI is connected, the latter trips 80% or 90% of the time or so consistently (like 4 trips for every 5 switchings).

This is only a guess as I don't have the schematic available, but I would think the Siemens is shunting the inductive component thus preventing trips on the Siemens GFCI.
 

junkhound

Senior Member
Location
Renton, WA
Occupation
EE, power electronics specialty
Here is another clue. If I connect the shaded pole motor to a Siemens GCFI breaker (which doesn't trip) in series to the Leviton based GFCI. Both won't trip.

How come putting the Siemens GFCI breaker between the shaded pole motor and the Leviton based GFCI outlet won't trip the latter?

If only the shaded pole motor and Leviton based GFCI is connected, the latter trips 80% or 90% of the time or so consistently (like 4 trips for every 5 switchings).

1st thought - inductance of
Siemens CT added in series with the Leviton offsets resonant frequency enough tht the Leviton does not trip.
 

tersh

Senior Member
Location
new york
Btw.. for loads like washing machine which doesn't trip the Leviton based GFCI outlets, is there nothing wrong by connecting two GFCI in series for backup in case one fails?

I plan to put the 240v GFCI receptacles (which doesn't have auto-monitoring self test mentioned in UL 2015) near wet areas but at the same time the breaker that would protect them would be the Siemens 2-pole GFCI breakers (240v) with
auto-monitoring self test mentioned in UL 2015.

Both trip at 5mA. The problem with GFCIs is if they become defective (the relays for example). It will remain energized and you won't know it doesn't work anymore. So the GFCI receptacles would be the backup in case the Siemens breakers fail. Or vice versa.


 
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
EC - retired
Btw.. for loads like washing machine which doesn't trip the Leviton based GFCI outlets, is there nothing wrong by connecting two GFCI in series for backup in case one fails?

I plan to put the 240v GFCI receptacles (which doesn't have auto-monitoring self test mentioned in UL 2015) near wet areas but at the same time the breaker that would protect them would be the Siemens 2-pole GFCI breakers (240v) with
auto-monitoring self test mentioned in UL 2015.

Both trip at 5mA. The problem with GFCIs is if they become defective (the relays for example). It will remain energized and you won't know it doesn't work anymore. So the GFCI receptacles would be the backup in case the Siemens breakers fail. Or vice versa.


Test them once a month like you’re supposed to, or add a third just in case the other two fail.
 

mopowr steve

Senior Member
Location
NW Ohio
Occupation
Electrical contractor
Does this occur constantly when the shaded pole motor was shut off? My experience is once for every two tries (or more) or 50% (or 75%) of the time. How about your experiences?

At the time, this has been quite a few years ago. When I was experiencing this problem I would say about 50% randomly.

I am led to believe that many of the exhaust fan manufacturers are onto this as many of the fans I’ve installed for the past few years have a suppression capacitor paralleled with the motor leads.
 
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