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Thread: Leviton GFCI nuisance tripping and circuit analysis

  1. #11
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    Quote Originally Posted by mopowr steve View Post
    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?

  2. #12
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    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.
    - Resistance is Futile ..... (if less than < 1 ohm) -

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    Quote Originally Posted by ELA View Post
    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...29/rv4141a.pdf

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    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)
    Last edited by junkhound; 01-08-19 at 08:00 AM.

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    Quote Originally Posted by junkhound View Post
    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).

  6. #16
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    Quote Originally Posted by tersh View Post
    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.

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    Quote Originally Posted by tersh View Post
    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.

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    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.



  9. #19
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    Quote Originally Posted by tersh View Post
    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.
    Tom
    TBLO

  10. #20
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    Quote Originally Posted by tersh View Post
    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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