# Thread: Leviton GFCI nuisance tripping and circuit analysis

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Originally Posted by gar
190111-0830 EST

tersh:

You continue to have false impressions because you do not go back to basics.

Look at the GFCI datasheet for the trip time characteristic. There is an inverse time relationship, electronic in this case, relative to current. The 5 mA is after a moderately long time relative to how little time it takes for you to detect a shock. Further you can detect a shock at a much lower level than 5 mA.

See https://pdfs.semanticscholar.org/368...68f166bb3d.pdf
1 mA looks to be a better level for detectability for ordinary people. An interesting side note is that John Swets is referenced in this discussion. I first met him in 1953 when I was in a psychology class taught by Wilson (Spike) P. Tanner. Tanner and Swets were both PhD students at the time working on signal detectability, and running vision experiments. I became a subject, about \$1 per hour. That summer I started building test equipment for Tanner's experiments.

Note that a 1 mA shock could kill you indirectly. You stand on a ladder, get shocked, fall off, crack your head on the floor, and die.

At 5 mA you will feel a substantial shock.

What is a surge, transient, impulse, RF, etc. Their meanings are all dependent upon context.

More later possibly.

.
Let's say one accidentally touch a live wire with the feet on ground, and the source is 3A. When the sense coil detects 5mA leakage, it triggers the IC to open the relay. But before the relay open. Can't it pass more than 5mA? Maybe 100mA? But 100mA is lethal dose already. So could china made GFCI be slower to respond. How do they test what mA of current are actually passed before the relay open say the trigger ampere is really 5mA?

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Originally Posted by tersh
Let's say one accidentally touch a live wire with the feet on ground, and the source is 3A. When the sense coil detects 5mA leakage, it triggers the IC to open the relay. But before the relay open. Can't it pass more than 5mA? Maybe 100mA? But 100mA is lethal dose already. So could china made GFCI be slower to respond. How do they test what mA of current are actually passed before the relay open say the trigger ampere is really 5mA?
Explain the source is 3A. I would be more concerned with the voltage of the source.

If you do not have any testing labs, such as UL, you are taking the word of the manufacturer that their equipment works as they claim. How they test is up to them. They may test it on 100 __________, and if 95% of them live it's good enough. They may not test at all.

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Originally Posted by tersh
Let's say one accidentally touch a live wire with the feet on ground, and the source is 3A. When the sense coil detects 5mA leakage, it triggers the IC to open the relay. But before the relay open. Can't it pass more than 5mA? Maybe 100mA? But 100mA is lethal dose already. So could china made GFCI be slower to respond. How do they test what mA of current are actually passed before the relay open say the trigger ampere is really 5mA?
Here is a 70 Year old chart from Dalziel, data from zapping a few thousand pigs and sheep in lieu of people.
40 years later it was also established that 'chance' plays a role for short duration shocks, as the shock has to occur during the T-wave (per EKG) fro fibrillation to occur.
Note that these levels are fatal to 'only' 1/2 of 1% of the sheep and pigs tht got zapped at that level.

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5. gar
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190111-1330 EST

tersh:

RF (Radio Frequency) dating back to probably before 1900, possibly not by that name.

See https://en.wikipedia.org/wiki/Guglielmo_Marconi

Radio frequencies are reasonably from about 50 kHz to very high frequencies. However, there are radio transmissions around 70 Hz to communicate with underwater submarines. Rightfully these are radio frequency frequencies, just not common. Radio frequencies can be transmitted thru the ether or by a conductor.

Generally radio frequencies are considered to be above the audio spectrum.

A 1 microsecond pulse every 1/10,000 sec is in the radio frequency spectrum, but not usually described as RF, but may cause RFI (radio frequency interference), either by radiation or conduction.

.

6. Originally Posted by gar
Generally radio frequencies are considered to be above the audio spectrum.
There are radio frequencies well below 20 kHz that are not audible. Radio and audio waves are completely different.

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Originally Posted by gar
Here is something disturbing for 240v users especially since the only GFCI receptacle model in the world was assembled by an unknown company. Meiji is just one OEM customer of this unknown company that assembled the cloned Fairchild chip. The first url above mentioned:

"
At voltages greater than 150 V, the resistance of the human body decreases dramatically and the fault current flowing through the body increases to unsafe levels requiring impossibly fast trip time. The purpose of the grounding conductor is to prevent the case or cabinet of a piece of equipment from exceeding 150 V if an energized conductor faults to it. The resulting current through the grounding conductor will also trip the GFCI to eliminate the danger of fibrillation."

The same url gave this formula

T = (20/I)^1.43

where T is in sec and
I
is in mA, and shown in Figure 3. Note that at currents greater than 300 mA, the delay is fixed at 20 msec.

For 120v. What is the resistance of the human body and if the fault current is 1A. How much current can pass between your two hands passing through the heart? What about at 240v?

Assuming the fault current of 1A can pass through your body. Then computing for T given I = 1000mA

T=(20/1000)^1.43 = 0.0037 second or 3.7millisecond

In the second url is this graph:

Before the above graph is this statement:

"What a Ground Fault Current Interrupter does not:

2.
It
does not
limit the magnitude of ground fault current. It does limit the length of time that a ground fault will flow. In other words, you will still receive a severe shock during the time it takes the GFCI device to trip “off.” See Figure 3"

If the current passing through the human body is 1A. The tripping time must be 0.0037 second which is not possible for GFCI.

For 240v. What is the resistance and maximum current that can really pass through the body so we can accurately compute for T and decide if the 240v cloned GFCI outlet sold worldwide is useless for utmost safety.

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Originally Posted by tersh
Here is something disturbing for 240v users especially since the only GFCI receptacle model in the world was assembled by an unknown company. Meiji is just one OEM customer of this unknown company that assembled the cloned Fairchild chip. The first url above mentioned:

"
At voltages greater than 150 V, the resistance of the human body decreases dramatically and the fault current flowing through the body increases to unsafe levels requiring impossibly fast trip time. The purpose of the grounding conductor is to prevent the case or cabinet of a piece of equipment from exceeding 150 V if an energized conductor faults to it. The resulting current through the grounding conductor will also trip the GFCI to eliminate the danger of fibrillation."

The same url gave this formula

T = (20/I)^1.43

where T is in sec and
I
is in mA, and shown in Figure 3. Note that at currents greater than 300 mA, the delay is fixed at 20 msec.

For 120v. What is the resistance of the human body and if the fault current is 1A. How much current can pass between your two hands passing through the heart? What about at 240v?

Assuming the fault current of 1A can pass through your body. Then computing for T given I = 1000mA

T=(20/1000)^1.43 = 0.0037 second or 3.7millisecond

In the second url is this graph:

Before the above graph is this statement:

"What a Ground Fault Current Interrupter does not:

2.
It
does not
limit the magnitude of ground fault current. It does limit the length of time that a ground fault will flow. In other words, you will still receive a severe shock during the time it takes the GFCI device to trip “off.” See Figure 3"

If the current passing through the human body is 1A. The tripping time must be 0.0037 second which is not possible for GFCI.

For 240v. What is the resistance and maximum current that can really pass through the body so we can accurately compute for T and decide if the 240v cloned GFCI outlet sold worldwide is useless for utmost safety.

I was thinking if using isolation transformer for fridge for 240v users is safer than a 240v GFCI from an unknown manufacturer and especially with the information above.

Say. What would happen when you connect an GFCI to an isolation transformer. Would it trip if there is leak from one live wire to ground? Since the ground is isolation, it shouldn't trip, should it?

But connecting the shaded pole motor to the Meiji GFCI outlet and to a medical isolation transformer.

The shaded pole motor still trips 4 out of 5 switchings (sometimes 100% trip 5 out of 5). The isolation transformer totally isolate the ground from source. It is a high quality medical isolation transformer with datasheet at http://catalog.triadmagnetics.com/Asset/VPM240-2080.pdf I got precisely to make sure the isolation is top notch. It even has dieelectric shielding between primary and secondary of the toroid which is difficult to manufacturer that is why it costs a lot.

If you connect GFCI to a true isolation transformer, what instance can the GFCI still trip when the ground is supposed to be separated already?

9. Originally Posted by tersh
Say. What would happen when you cnnecto an GFCI to an isolation transformer. Would it trip if there is leak from one live wire to ground? Since the ground is isolation, it shouldn't trip, should it?

If you connect GFCI to a true isolation transformer, what instance can the GFCI still trip when the ground is supposed to be separated already?
Theoretically speaking, on a genuinely isolated, ungrounded electrical supply, a GFCI cannot detect when there is a connection between a supply conductor and earth. GFCI's serve no purpose on ungrounded systems.

In your experiments, there has been nothing to even suggest that the GFCI was tripping due to an unintentional leakage current to earth.

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Originally Posted by LarryFine
There are radio frequencies well below 20 kHz that are not audible. Radio and audio waves are completely different.
So what is the relationship between inductive kick and LC filter? What part of inductive kick can LC filter able to filter?

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