Leviton GFCI nuisance tripping and circuit analysis

[tersh]

190114-2427 EDT

tersh:

As redrawn the diode near the trip coil makes perfect sense. And it will keep the trip coil energized longer.

I have no idea why the ??? thing would be needed.

.

The thermal fuse should be conducting in the two legs, right? I couldn't measure any continuity in it. And it's connected to the solenoid. It is possible that when pin 7 and 8 was removed, the thermal fuse opened and hence the solenoid couldn't be activated anymore even if there is capacitive coupling at C3.

Therefore it's still possible you were right the capactive coupling in the C3 can trip it. Leviton can try it themselves. Whether it's a bug in the chip or the C3.

Also, how come when you shorted the gate and cathode. It can no longer trip? Last I handled SCR was over 20 years ago.

 

[tersh]

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.

.

Something important to share. In the original Leviton circuit, did you see the distance between SCR and C3 an inch? In the china gfci, the distance between SCR and C3 is only mere 1/4 inch. Here:

The whole circuit is only about 2.25 inches long:

This was the reason they couldn't fit a mechanical reset because it needed many spacing.

Anyway. The US Leviton is much larger. So maybe someone can test on the actual Leviton because there is possibility the inductive kick in both may be via different mechanisms. Your theory may be correct for the actual Leviton. But please share something in the following before I move on from this. .

In the original Leviton circuit using this bare diagram which I have almost memorized:

1. How come if the SCR is 1" away from C3. It can more likely produce capacitive coupling? Also I think you are saying the capacitive coupling source is the red path above, right? And it getting into the gate? but why does long distance make capacitive coupling more likely? This is to understand other circuits too and not just it.

2. If you short the gate and cathode of the SCR, how much the false trigger disappears? When you short the cathode to the gate, is it not like the gate is triggered?

3. My thesis in college engineering was ultrasonic cleaning machine. I could have focused on GFCI back then. Whatever, it would be easy to put the solenoid back or other load to test whether the shaded pole motor inductive kick can trigger it without the chip. I'll let you know. I spent 5 years in college and it would be crazy if I couldn't even do this. But I generally avoid electronics because the cell or neurons in biology is way advanced than any electronics.

 

[gar]

190115-0811 EST

tersh:

Your 1 --- Take two straight wires of of some fixed dimensions and spaced a fixed distance apart, then the capacitance between the wires is proportional to length. Longer length more capacitance. Also as the length of a wire increases so does its inductance.

Your red line is in the wrong place. There is already resistive continuity for that path. The red line needs to end on the gate, and start at the upper power line wire.


Your 2 --- When the gate is shorted to the cathode it is very difficult to get a trigger voltage to the gate.


Your top picture --- The C3 is in a very good location. In the Leviton I looked at there was a much longer trace.

In the present circuit with no IC installed, but otherwise all the circuit for the gate is unaltered, is there any false triggering?

If you started with a new circuit and removed the 1N4004 diode that feeds pin 5, labeled "line", this removes power to the IC, then would false triggering occur. If false triggering was eliminated, then this would tend to indicate that SCR triggering was coming from the IC. It is possible you could remove the 1N4004 to perform the test, and then reinstall it so this might not be costly.

.

 

[tersh]

190115-0811 EST

tersh:

Your 1 --- Take two straight wires of of some fixed dimensions and spaced a fixed distance apart, then the capacitance between the wires is proportional to length. Longer length more capacitance. Also as the length of a wire increases so does its inductance.

Your red line is in the wrong place. There is already resistive continuity for that path. The red line needs to end on the gate, and start at the upper power line wire.

But how could it start at the upper power line wire? There is no path to the gate except via the solenoid. And even if it passes via the solenoid, it can't get into the gate. So what path were you assuming?

Your 2 --- When the gate is shorted to the cathode it is very difficult to get a trigger voltage to the gate.


Your top picture --- The C3 is in a very good location. In the Leviton I looked at there was a much longer trace.

In the present circuit with no IC installed, but otherwise all the circuit for the gate is unaltered, is there any false triggering?

I won't know until I added the solenoid back to the anode of the SCR. In place of the solenoid, what load can you put so it can indicate if the gate is triggering? What must be the voltage and current of the load (to replace the solenoid)?

If you started with a new circuit and removed the 1N4004 diode that feeds pin 5, labeled "line", this removes power to the IC, then would false triggering occur. If false triggering was eliminated, then this would tend to indicate that SCR triggering was coming from the IC. It is possible you could remove the 1N4004 to perform the test, and then reinstall it so this might not be costly.

.

I may get a new one and test again because I can swear that when pin 1,2,3 (or sense coil input) disconnected. I can still use the Test Button which opens the contacts. this was about a dozen times. I don't know if it is transient or something wrong with the circuit. I need to get to the bottom of this because the Test button needs to be push monthly and need to be sure it is genuine.

In case I get a new one. I must first disconnect pin 1,2,3 to check if the Test button still works and why. And then remove the diode to check your theory right?

I won't put back in service anything that has been altered already. But its important to check that the GFCI is working property because it has important protection functions.

 

[gar]

190115-0914 EST

tersh:

The hot wire on the circuit board to the wire to the gate is a capacitor, but very small. Not a conductive wire, but a capacitor is a conductor for high frequencies. Then you have a shunt capacitor, C3, from gate to cathode, thus is formed a capacitive voltage divider. It takes about a volt, gate to cathode, to trigger the SCR.

If the transient voltage reaches 5000 V, then the coupling capacitance can be 1/5000 of the capacitance of C3 and produce 1 V at the gate. In the circuit shown C3 is 10,000 pfd. Thus, 2 pfd (not much) could result in 1 V.

If the trace to the gate is long, then the coupling capacitance is increased. If the C3 is moved further from the gate, long lead, then its inductance increases and at high frequencies tends to reduce the effectiveness of C3.

In your test order do the diode removal first before the 1, 2, 3 lead test. The diode should be moderately easy to reinstall.

Reconnect the solenoid. It is your best indicator.

.

 

[gar]

190115-1203 EST

tersh:

If at any time you do try to do some scope measurements, then I suggest you want a 240 to 240 isolation transformer to power the test. You would ground the input lead to the GFCI that has a conductive path to pin 4, GND, of the IC.

.

 

[tersh]

190115-0914 EST

tersh:

The hot wire on the circuit board to the wire to the gate is a capacitor, but very small. Not a conductive wire, but a capacitor is a conductor for high frequencies. Then you have a shunt capacitor, C3, from gate to cathode, thus is formed a capacitive voltage divider. It takes about a volt, gate to cathode, to trigger the SCR.

Just to verify on your statement about "The hot wire on the circuit board to the wire to the gate is a capacitor". Did you mean a physical capacitor, or just capacitive coupling (by air only) between the hot wire to the wire to the gate? If a physical capacitor. I don't see any physical capacitive between hot wire to the wire to the gate.

Also any idea what voltage and current does Pin 7 used to trigger the SCR gate? Or what voltage to use to manually trigger the gate to be sure any reconnected solenoid is working? (If necessary)

​

If the transient voltage reaches 5000 V, then the coupling capacitance can be 1/5000 of the capacitance of C3 and produce 1 V at the gate. In the circuit shown C3 is 10,000 pfd. Thus, 2 pfd (not much) could result in 1 V.

If the trace to the gate is long, then the coupling capacitance is increased. If the C3 is moved further from the gate, long lead, then its inductance increases and at high frequencies tends to reduce the effectiveness of C3.

In your test order do the diode removal first before the 1, 2, 3 lead test. The diode should be moderately easy to reinstall.

Reconnect the solenoid. It is your best indicator.

.

About

"If at any time you do try to do some scope measurements, then I suggest you want a 240 to 240 isolation transformer to power the test. You would ground the input lead to the GFCI that has a conductive path to pin 4, GND, of the IC."

My test bench now is protected by GFCI in the outlet with 240v:240v medical grade isolation transformer (I bought to use with fridge thinking all GFCI trips.. but no.. the Siemens 2 pole GFCI breaker never trip more than a week now) and with 3M electrical gloves. Back in college engineering labs. We never used any of those protection. But I guess they do now.

Say, how much of the inductive kicks can show up in the oscilloscope?

The Meiji GFCI store will open 4 hours from now so I'll buy 2 pcs later for testing the removal of diode to see if shaded pole motor would still trip it and why removing pin 1,2,3 can still somehow cause Test to work (weird).​

 

[gar]

190115-2130 EST

tersh:

Any two conductors with a dielectric between them, can be a vacuum, forms a capacitor. When it is an unwanted capacitance it may be called stray capacitance. The capacitance I am talking about is not an explicit component, but a result of conductors and non conductive material between them.

Probably less than 1 V between gate and cathode will trigger the SCR. As a trigger use 5 or 6 V thru a 1 k resistor. The 1k is a current limiter. Don't backfeed current or voltage into pin 7 of the IC.

In close proximity to a socket if I cycle a two bulb magnetic ballast 8' Slimline fixture I can see several thousand volt transients between hot and neutral. Go 50 ft away and I would expect much smaller peak values. Never bothered with the latter experiment. All I really wanted to do is make big transients.

You need a scope that can capture and display single shot waveforms. Probably pulse durations might be in the 1 microsecond range. A divide by 100 probe would be useful, most are divide by 10 or 1.

.

 

[ptonsparky]

Just to verify on your statement about "The hot wire on the circuit board to the wire to the gate is a capacitor". Did you mean a physical capacitor, or just capacitive coupling (by air only) between the hot wire to the wire to the gate? If a physical capacitor. I don't see any physical capacitive between hot wire to the wire to the gate.

Also any idea what voltage and current does Pin 7 used to trigger the SCR gate? Or what voltage to use to manually trigger the gate to be sure any reconnected solenoid is working? (If necessary)

​

About

My test bench now is protected by GFCI in the outlet with 240v:240v medical grade isolation transformer (I bought to use with fridge thinking all GFCI trips.. but no.. the Siemens 2 pole GFCI breaker never trip more than a week now) and with 3M electrical gloves. Back in college engineering labs. We never used any of those protection. But I guess they do now.

Say, how much of the inductive kicks can show up in the oscilloscope?

The Meiji GFCI store will open 4 hours from now so I'll buy 2 pcs later for testing the removal of diode to see if shaded pole motor would still trip it and why removing pin 1,2,3 can still somehow cause Test to work (weird).​

I set up test similar to yours with two shaded pole fan motors. One with the rotor one without.

I could measure a 560 volt inductive kick with my Fluke at 1ms. Even a mediocre scope should do that. No rotor showed the highest kickback as well as the highest milligaus of about 3 times the other. I put a snubber on each and brought that 560 down to 172-174.

My goal was to see how well the snubbers worked, and if I could trip a GFCI. I didn’t.

eta. FWIW The hots to each fan motor were switched separately with the neutrals tied together and switched. All three contacts switched at the same time via an old PICO.

 

[tersh]

190115-0914 EST

tersh:

The hot wire on the circuit board to the wire to the gate is a capacitor, but very small. Not a conductive wire, but a capacitor is a conductor for high frequencies. Then you have a shunt capacitor, C3, from gate to cathode, thus is formed a capacitive voltage divider. It takes about a volt, gate to cathode, to trigger the SCR.

If the transient voltage reaches 5000 V, then the coupling capacitance can be 1/5000 of the capacitance of C3 and produce 1 V at the gate. In the circuit shown C3 is 10,000 pfd. Thus, 2 pfd (not much) could result in 1 V.

If the trace to the gate is long, then the coupling capacitance is increased. If the C3 is moved further from the gate, long lead, then its inductance increases and at high frequencies tends to reduce the effectiveness of C3.

In your test order do the diode removal first before the 1, 2, 3 lead test. The diode should be moderately easy to reinstall.

Reconnect the solenoid. It is your best indicator.

.

I went to the attic to get my second solder used back in college electronic engineering course days and got ready.

I then bought a new Meiji outlet. Before I disconnected the diode, I tested it with the shaded pole motor. It tripped 4 out of 5 times. This means it is consistent with the entire Meiji stock. The sales personnel told me companies order them by the hundreds and he just sold 250 pcs to a single company.


Then I disconnected the diode as you asked. The shaded pole motor never tripped again after switching it on and off for more than 20 times!

So it is the chip that is the cause of the tripping and not capacitive coupling to the gate (at least for this particular china made GFCI because in the US, who knows, it may be the mechanism). What I can't understand is if Shanghai Fudan Microelectronics Ltd. Co who made the FM2141 just designed it from scratch. How come it trips similar to the Leviton? Maybe Shanghai Fudan just copied the entire chip, isn't it?

Next I'll remove pin 1,2,3 and try the Test button. Before in the first unit. I also removed pin 1,2,3 (all sense coil input) and the tripping still occurs proving it's not related to the first sense coil or the grounded neutral sense coil, but inside the chip itself.

Gar, before I'll remove pin 1,2,3.. what do you want me to do first? Because I don't want to try a third test unit.

The tripping may be these particular Shanghai Fudan FM2141 and Fairchild RV4141A chip only. The new Leviton models in the US with auto-monitoring self test may be more resistant? What chip did you use ptonsparky when you tried it with your shaded pole motor and it never trip?

 

[tersh]

I went to the attic to get my second solder used back in college electronic engineering course days and got ready.

I then bought a new Meiji outlet. Before I disconnected the diode, I tested it with the shaded pole motor. It tripped 4 out of 5 times. This means it is consistent with the entire Meiji stock. The sales personnel told me companies order them by the hundreds and he just sold 250 pcs to a single company.


Then I disconnected the diode as you asked. The shaded pole motor never tripped again after switching it on and off for more than 20 times!

So it is the chip that is the cause of the tripping and not capacitive coupling to the gate (at least for this particular china made GFCI because in the US, who knows, it may be the mechanism). What I can't understand is if Shanghai Fudan Microelectronics Ltd. Co who made the FM2141 just designed it from scratch. How come it trips similar to the Leviton? Maybe Shanghai Fudan just copied the entire chip, isn't it?

Next I'll remove pin 1,2,3 and try the Test button. Before in the first unit. I also removed pin 1,2,3 (all sense coil input) and the tripping still occurs proving it's not related to the first sense coil or the grounded neutral sense coil, but inside the chip itself.

Gar, before I'll remove pin 1,2,3.. what do you want me to do first? Because I don't want to try a third test unit.

The tripping may be these particular Shanghai Fudan FM2141 and Fairchild RV4141A chip only. The new Leviton models in the US with auto-monitoring self test may be more resistant? What chip did you use ptonsparky when you tried it with your shaded pole motor and it never trip?

Btw this is the appearance of the 2 meiji. The top is normal (with greenish yellowish light). In the bottom with disconnected diode (to pin 5). There is both greenish yellowish and red light. You can't press any key. Neither Reset nor Test will work in the latter. Therefore if you remove the diode and you didn't press the Reset. You can't reset it anymore (unlike in US where reset is mechanical).

 

[gar]

190115-2419 EST

tersh:

Now that it appears the false trigger comes from the IC, then how does the transient get into the IC?

Since the diode is presently removed measure the DC resistance from pin 5 to pin 6 using both polarities, reverse leads. It would be very nice if this was virtually 0 ohms.

With your unaltered GFCI with power applied what is the DC voltage between pin 4, the DC common reference, meter negative, and pin 5, and pin 6? Should get positive readings. Might switch to AC and see what these readings are, looking for ripple? Also possibly measure DC and AC voltage difference between pin 5 and pin 6? This would be near zero if the resistance between 5 and 6 was near zero.

Before reinstalling the diode. If we find that pin 5 is essentially directly connected to pin 6, and that DC voltage between 4 and 6 is quite constant, low ripple from the working unit. Then it would be interesting to supply a battery voltage between pin 4 (negative of battery), and pin 5 (battery +) of whatever value was measure on the working unit. This would power the IC. If false tripping did not occur, then the transient is likely getting in thru the diode, and pin 5.

If false triggering did occur, then we have to try to figure out how it enters the IC.

.

 

[gar]

190115-2534 EST

tersh:

An additional thought. Once you reinstall the 1N4004, and the circuit is back to working, and with the high probability of false trips again occurring, then measure the peak voltage between pin 5 and pin 4. Then pick a Zener diode with a voltage somewhat above the measured peak, and place this across pin 5 to pin 4 with the cathode on pin 5. This would clamp any transient voltage at the 1n4004 output to the Zener voltage. A specialized transient limiting Zener is called a Transorb.

.

 

[tersh]

190115-2419 EST

tersh:

Now that it appears the false trigger comes from the IC, then how does the transient get into the IC?

Since the diode is presently removed measure the DC resistance from pin 5 to pin 6 using both polarities, reverse leads. It would be very nice if this was virtually 0 ohms.

With your unaltered GFCI with power applied what is the DC voltage between pin 4, the DC common reference, meter negative, and pin 5, and pin 6? Should get positive readings. Might switch to AC and see what these readings are, looking for ripple? Also possibly measure DC and AC voltage difference between pin 5 and pin 6? This would be near zero if the resistance between 5 and 6 was near zero.

Before reinstalling the diode. If we find that pin 5 is essentially directly connected to pin 6, and that DC voltage between 4 and 6 is quite constant, low ripple from the working unit. Then it would be interesting to supply a battery voltage between pin 4 (negative of battery), and pin 5 (battery +) of whatever value was measure on the working unit. This would power the IC. If false tripping did not occur, then the transient is likely getting in thru the diode, and pin 5.

If false triggering did occur, then we have to try to figure out how it enters the IC.

.

I measured the resistance between pin 5 and 6 as you asked with the diode disconnected. It was not zero but varying from about 2.75Mohm to 4.6Mohm (this is with diode disconnected and the red light on).

I reconnected the diode and tested the shaded pole motor. It tripped consistently 4 out of 5. High probability is an understatement. It's more like consistently.

I reconnected the diode because I was eager to see if the Test button could still work with pin 1 disabled. Lo and behold. When I turned on the unit. There was a red light and loud click as the solenoid kept vibrating (maybe from continuous tripping due to Rset becoming zero). Then the SCR got fried:

Now I remember Meiji telling me that when customers push the reset and test button many times continuous in 2 seconds, the circuit can get fried. So they won't honor warrantee if the customer used it like switches. What kind of SCR did the china clone maker put that can make it burst when the gate is repeatedly triggered??

Refusing to give up without making sure the Test button is not fake. I sacrificed the third and definitely final Meiji GFCI receptacle. Not wanting another fried circuit. I removed pin 6, 1, 2, 3 simultaneously. This happened before and no problem.

I noticed the shaded pole motor no longer tripped. Actually 2 days ago when I first removed pin 6 in the first experiment unit. The motor still tripped 4 out of 5 times. But when I removed pin 1,2,3, the first time I tested it. The shaded pole motor didn't trip for 10 switches. But at 11th time. It tripped so I thought the same old problem. I didn't check it much during that time because focusing on the Test button which seemed to still work. Not long I removed pin 7 and 8 which stopped any trigger then remove the chip by removing the remaining pin 4 and 5.

Now testing the Test button with the third receptacle with missing pin 6, 1, 2,3.. I pressed it a hundred times and only once did it trip. Similarly to shaded pole motor. I switched it about 50 times or more. And one once did it trip.

Analyzing it. I think the chip is simply malfunctioning when the SCR got triggered from 1 in 100 Test button and shaded pole motor switching. Not from inductive kick or Test button leakage but simply the chip doing it 1 out of a hundred. All the pins 4 (ground), 5 (line), 7 (SCR trigger), 8 (trip delay) is still on.

So the inductive kick seemed to affect the input. Since I pulled out the second grounded neutral sense coil 3 days ago and it still tripped. The conclusion seemed to be the inductive kick is causing capacitive coupling in the sense coil input in pin 1, 2, 3. Is this possible? Look at this circuit diagram again:

Note in my first experiment circuit. The second grounded neutral sense coil was pulled out. And pin 6, 1, 2, 3 gone. Since the remaining first sense coil couldn't be the recipient of the inductive kick (could it?), then it's either the capacitor C1 or Rset or Rin or the wires leading to pin 1, 2, 3. Is this possible?

I'm taking time to test all of it because in the Philippines where we were not ruled by UL or NEC. Either people never put any GCFI or a company putting 250 pieces in every outlet. Me too. I'll replace all outlet with GFCI outlet. Mike Holt said this may occur in the US in 2021 so may as well do it now. Hence it is important to know whether the Meiji works. I think it works well. Only problem with it is its manual saying the circuit has UL 2015 auto-monitoring self test which it doesn't.

I can replace the third pcb chip with missing pin 6,1,2,3 from another 2nd pcb with working chip after I upgraded my soldering tool or let my former electronic engineering classmates or professors do it. But I won't yet as I can finally switch the shaded pole motor 50 times or a hundred times with only one trip or so, instead of 4 out of 5 trips in working unit (very consistently).

Besides sense coil pin 1, 2, 3 input wires being recipient of capacitive coupling and inductive kick. Any other theories?

 

[tersh]

I measured the resistance between pin 5 and 6 as you asked with the diode disconnected. It was not zero but varying from about 2.75Mohm to 4.6Mohm (this is with diode disconnected and the red light on).

I reconnected the diode and tested the shaded pole motor. It tripped consistently 4 out of 5. High probability is an understatement. It's more like consistently.

I reconnected the diode because I was eager to see if the Test button could still work with pin 1 disabled. Lo and behold. When I turned on the unit. There was a red light and loud click as the solenoid kept vibrating (maybe from continuous tripping due to Rset becoming zero). Then the SCR got fried:

Now I remember Meiji telling me that when customers push the reset and test button many times continuous in 2 seconds, the circuit can get fried. So they won't honor warrantee if the customer used it like switches. What kind of SCR did the china clone maker put that can make it burst when the gate is repeatedly triggered??

Refusing to give up without making sure the Test button is not fake. I sacrificed the third and definitely final Meiji GFCI receptacle. Not wanting another fried circuit. I removed pin 6, 1, 2, 3 simultaneously. This happened before and no problem.

I noticed the shaded pole motor no longer tripped. Actually 2 days ago when I first removed pin 6 in the first experiment unit. The motor still tripped 4 out of 5 times. But when I removed pin 1,2,3, the first time I tested it. The shaded pole motor didn't trip for 10 switches. But at 11th time. It tripped so I thought the same old problem. I didn't check it much during that time because focusing on the Test button which seemed to still work. Not long I removed pin 7 and 8 which stopped any trigger then remove the chip by removing the remaining pin 4 and 5.

Now testing the Test button with the third receptacle with missing pin 6, 1, 2,3.. I pressed it a hundred times and only once did it trip. Similarly to shaded pole motor. I switched it about 50 times or more. And one once did it trip.

Analyzing it. I think the chip is simply malfunctioning when the SCR got triggered from 1 in 100 Test button and shaded pole motor switching. Not from inductive kick or Test button leakage but simply the chip doing it 1 out of a hundred. All the pins 4 (ground), 5 (line), 7 (SCR trigger), 8 (trip delay) is still on.

So the inductive kick seemed to affect the input. Since I pulled out the second grounded neutral sense coil 3 days ago and it still tripped. The conclusion seemed to be the inductive kick is causing capacitive coupling in the sense coil input in pin 1, 2, 3. Is this possible? Look at this circuit diagram again:

Note in my first experiment circuit. The second grounded neutral sense coil was pulled out. And pin 6, 1, 2, 3 gone. Since the remaining first sense coil couldn't be the recipient of the inductive kick (could it?), then it's either the capacitor C1 or Rset or Rin or the wires leading to pin 1, 2, 3. Is this possible?

I'm taking time to test all of it because in the Philippines where we were not ruled by UL or NEC. Either people never put any GCFI or a company putting 250 pieces in every outlet. Me too. I'll replace all outlet with GFCI outlet. Mike Holt said this may occur in the US in 2021 so may as well do it now. Hence it is important to know whether the Meiji works. I think it works well. Only problem with it is its manual saying the circuit has UL 2015 auto-monitoring self test which it doesn't.

I can replace the third pcb chip with missing pin 6,1,2,3 from another 2nd pcb with working chip after I upgraded my soldering tool or let my former electronic engineering classmates or professors do it. But I won't yet as I can finally switch the shaded pole motor 50 times or a hundred times with only one trip or so, instead of 4 out of 5 trips in working unit (very consistently).

Besides sense coil pin 1, 2, 3 input wires being recipient of capacitive coupling and inductive kick. Any other theories?

Another thing (to add to the above). If gar noticed there was a 1" distance from C3 to the gate in the US Leviton PCB circuitry. It is more than 1" cooper path for all of Pin 1, 2, 3 in the china gfci. Can capacitance coupling formed here and how does it affect the input?

The yellow arrows are the long paths of Pin 1, 2, and 3 (yes 3, look at back of the circuit, pin 3 has longest path).

And remember I just removed pin 1, 2, 3 and 6. And it's not 2nd grounded neutral sense coil because when I pulled out the entire winding in the first test unit, the shaded pole motor still tripped 4 out of 5 times, but not now. Only randomly once in 50-100 switchings just like the Test button so this may be noise from removal of Pin 6 (which is supposed to smoothen the pulsing DC from pin 5?)

 

[tersh]

Another thing (to add to the above). If gar noticed there was a 1" distance from C3 to the gate in the US Leviton PCB circuitry. It is more than 1" cooper path for all of Pin 1, 2, 3 in the china gfci. Can capacitance coupling formed here and how does it affect the input?

The yellow arrows are the long paths of Pin 1, 2, and 3 (yes 3, look at back of the circuit, pin 3 has longest path).

And remember I just removed pin 1, 2, 3 and 6. And it's not 2nd grounded neutral sense coil because when I pulled out the entire winding in the first test unit, the shaded pole motor still tripped 4 out of 5 times, but not now. Only randomly once in 50-100 switchings just like the Test button so this may be noise from removal of Pin 6 (which is supposed to smoothen the pulsing DC from pin 5?)

Today when I tried to turn on the shaded pole motor. The third test unit (with pin 1,2,3,6 removed) suddenly tripped and I have difficulting resetting it. I remembered that days ago even with pin 1,2,3,6 removed. It tripped reguarly. I don't know if removing pin 1,2,3 makes it less sensitive and it depends on the supply noises during time of the day that can affect other component. I'll observe more after I let someone transfer the IC from 2nd to the 3rd or replace the SCR of the 2nd. It seems the inductive kick and capacitive coupling can affect multiple components (wherever path is long), so different PCB (like Leviton, china clone) has different causes so don't base my finding (or even conclusion) and apply it to other pcbs.

If you are willing, Gar, I'd send you the water shaded pole motor which I no longer need (I avoid high milligauss appliance generally so would never use it anymore) and would send you the china clone GFCI so you can test it yourself as I don't have the necessary breath of knowledge like you to fully analyze it. Also Siemens emailed today regarding the Siemens 2-pole GFCI breakers:

"Sorry for the delay. Engineering has received new breakers from stock, which, when installed are configured the same as you have shown in the photos you sent with the angle on the connections.

Engineering has tested & indicate contact is sufficient for proper function of the breakers."

​

So I'd start to look for the most skilled electrician and install them. We pay electrician from $10 to $20 (best of them) a day and no owner or even engineer install any of them personally (of course).

 

[tersh]

Today when I tried to turn on the shaded pole motor. The third test unit (with pin 1,2,3,6 removed) suddenly tripped and I have difficulting resetting it. I remembered that days ago even with pin 1,2,3,6 removed. It tripped reguarly. I don't know if removing pin 1,2,3 makes it less sensitive and it depends on the supply noises during time of the day that can affect other component. I'll observe more after I let someone transfer the IC from 2nd to the 3rd or replace the SCR of the 2nd. It seems the inductive kick and capacitive coupling can affect multiple components (wherever path is long), so different PCB (like Leviton, china clone) has different causes so don't base my finding (or even conclusion) and apply it to other pcbs.

If you are willing, Gar, I'd send you the water shaded pole motor which I no longer need (I avoid high milligauss appliance generally so would never use it anymore) and would send you the china clone GFCI so you can test it yourself as I don't have the necessary breath of knowledge like you to fully analyze it. Also Siemens emailed today regarding the Siemens 2-pole GFCI breakers:

"Sorry for the delay. Engineering has received new breakers from stock, which, when installed are configured the same as you have shown in the photos you sent with the angle on the connections.

Engineering has tested & indicate contact is sufficient for proper function of the breakers."

​

So I'd start to look for the most skilled electrician and install them. We pay electrician from $10 to $20 (best of them) a day and no owner or even engineer install any of them personally (of course).

The electrician was scheduled to arrive early to plug in the second Siemens GFCI breaker to existing panel. So pondering if the china gfci outlet would trip. I hurriedly plug it to 120v Leviton power strip which I used to plug my TV, CCTV to avail of lower let through voltage. That's the reason the china gfci won't reset because it's 120v. Also it's weird that with 120v, the shaded pole motor has more tendency to trip.

But with 220v restored. The motor doesn't trip and I can Reset it again. I was talking about the third gfci test unit with pin 1,2,3,6 removed. However I want to share as complete information as possible. The other day when pin 1,2,3,6 removed, I really remembered it tripped more than now.

So when I have time. I'll connect the FM2141 chip in such a way I can remove any pin and connect it at will so I can trace the cause of the nuisance tripping. Nuisance tripping doesn't bother me because for fridges that trip, I could simply connect it to the Siemens GFCI which doesn't trip. But just want to take this opportunity to understand more about inductive kick, capacitive coupling and other stuff I didn't learn in college.

Theoretically can capacitive coupling occur to the wires leading to pin 1,2,3 that would make it produce a signal with same effect as sense coil current imbalance and erroneously trip the SCR?

 

[tersh]

The electrician was scheduled to arrive early to plug in the second Siemens GFCI breaker to existing panel. So pondering if the china gfci outlet would trip. I hurriedly plug it to 120v Leviton power strip which I used to plug my TV, CCTV to avail of lower let through voltage. That's the reason the china gfci won't reset because it's 120v. Also it's weird that with 120v, the shaded pole motor has more tendency to trip.

But with 220v restored. The motor doesn't trip and I can Reset it again. I was talking about the third gfci test unit with pin 1,2,3,6 removed. However I want to share as complete information as possible. The other day when pin 1,2,3,6 removed, I really remembered it tripped more than now.

So when I have time. I'll connect the FM2141 chip in such a way I can remove any pin and connect it at will so I can trace the cause of the nuisance tripping. Nuisance tripping doesn't bother me because for fridges that trip, I could simply connect it to the Siemens GFCI which doesn't trip. But just want to take this opportunity to understand more about inductive kick, capacitive coupling and other stuff I didn't learn in college.

Theoretically can capacitive coupling occur to the wires leading to pin 1,2,3 that would make it produce a signal with same effect as sense coil current imbalance and erroneously trip the SCR?

Gar, here is another important information. When I tried to reconnect pin 6 and actually did it. When I turned on the circuit, there was a red light with many clicks signifying the SCR was continuously being triggered and the solenoid clicking a lot. This was the same effect when Pin 1 was disconnected with pin 6 intact and burning the SCR. So since pin 6 is supposed to smoothen the pulsing DC at pin 5. Then without pin 6. It's like the circuit is half dead already. So this is the dilemma. By enabling pin 6. You can't remove pin 1,2,3 because this will make pin 7 trigger the SCR continuously that can burn the SCR. And I opened pin 6 again now, same condition as pin 6,1,2,3 disconnected and the motor didn't trip. Now one can make another interpretation that it doesn't trip anymore simply because the circuit is not functioning already, and not because of capacitive coupling in the wires leading to pin 1,2,3. What do you make of all this?

Without pin 6 to smoothen the pulsing DC in pin 5 (live), can any chip be able to function with pulsing DC?

 

[gar]

190116-2413 EST

tersh:

Last first.

Previously your ohmmeter reading between pins 5 and 6 was high. This implies some form of electronics between these pins. It is not a straight conductor. At this point we don't know what is between these pins. It is my belief that the 1 ufd capacitor connected between pin 6 and pin 4 (common) is a DC supply filter capacitor. Mostly because of its capacitance with respect to other capacitors. Without the capacitor there would be a large ripple on the internal to the IC DC supply.

With power supply filtering removed it is likely that the SCR could be pulsed every cycle, 60 times per second.

Transient noise to trigger the SCR is not going in thru the pin 6.

Transient noise could go in thru pin 5. That is what my suggested experiment with battery power might identify.

So since pin 6 is supposed to smoothen the pulsing DC at pin 5.

It would only smooth pin 5 if there was a good conductive path from 5 to 6. You have shown there is not a conductive path.

Had a crash of this post. Need to go to bed. More later.

.

 

[tersh]

190116-2413 EST

tersh:

Last first.

Previously your ohmmeter reading between pins 5 and 6 was high. This implies some form of electronics between these pins. It is not a straight conductor. At this point we don't know what is between these pins. It is my belief that the 1 ufd capacitor connected between pin 6 and pin 4 (common) is a DC supply filter capacitor. Mostly because of its capacitance with respect to other capacitors. Without the capacitor there would be a large ripple on the internal to the IC DC supply.

With power supply filtering removed it is likely that the SCR could be pulsed every cycle, 60 times per second.

In normal usage, the SCR is only triggered for half a cycle or 17ms for 60 Hz system enough for the contacts to open.

But here is the thing about pin 6 that is consistent. If you removed all input in pin 1,2,3 (sense coil input) and you didn't remove pin 6. It will continue to trigger the SCR until it melts and the solenoid overheats. But if you remove pin 6. You will initially hear weak vibrating that goes away after repeated off-on. Could the capacitor between pin 6 and 4 somehow make the Pin 7 trigger the SCR at continuous cycle?

Do you understand why if pin 1,2,3 is not connected, it will continue to trigger the SCR? But if pin 6 not connected. It would suppress that. Or could pin 6 somehow be related to the SCR instead of the internal circuit? What do you think?

Can you think of any scenario of pin 6 that can explain the above consistent observations?

Transient noise to trigger the SCR is not going in thru the pin 6.

Transient noise could go in thru pin 5. That is what my suggested experiment with battery power might identify.

It would only smooth pin 5 if there was a good conductive path from 5 to 6. You have shown there is not a conductive path.

Had a crash of this post. Need to go to bed. More later.

.

Is it possible the transient can enter pin 1,2,3 instead? It is possible the consistent transient that can make waterpik shaded pole motor trips any of those china GFCI at will 4 out of 5 times come from pin 1,2,3 while the sporatic random transient that you can't always get consistently come from pin 5 or line. When you remove pin 1,2,3,6. You get very long period without tripping. But occasionally it still trips which may come from the pin 5 or line.

Also in case the transient is messing with pin 1,2,3. Is it just passing through it and triggering pin 7 or can the transient somehow induce values in the 3 pins that falsely indicate inbalance current in the sense coil? There is a subtle difference between the two. What do you think?


For long message, try to select all and copy before submitting reply so if it crashes, at least you copied it and can paste it again.