Posted by John T on November 07, 2014 at 06:24:54 from (216.249.72.121):
In Reply to: GFCI dilemma resolved posted by George Marsh on November 06, 2014 at 15:23:22:
Okay gang, lets do some of the math and look at how the GFCI operates and respond to Georges post: This is kind of an Engineering analysis, it gets a little deep and technical, bear with me, but its just how I am "wired" after engineering school and 40 years:
If George is right?????? (I'm NOT saying he is or isn't, just using his figures, its his post, his info which I take at his word, and his question)
1) If the GFCI is drawing (per George, NOT me) 2.6 watts at 120 volts, that means its drawing 2.6/120 = 22 Milliamps just sitting there with its sensing electronics at work. NOT ME SAYING IM USING GEORGES INFO and if my math is right NO WARRANTY so don't anyone have a calf, I may well be wrong and likely am, so there lol
2) ME SAYING How the GFCI works is that if there is 5 milliamps less current flow in the Neutral then the Hot line conductor (5 milliamps of fault current being returned OTHER THEN the Neutral) IT TRIPS OPEN. So if George is right??? (using HIS info, not me saying) SURE if there's a current flow of 22 Milliamps in the Ground that's NOT in the Neutral, THE GFCI TRIPS.
BUT HERES COMES THE RUB
HOW AND MOST IMPORTANT WHERE DO YOU GET THAT 22 MILLIAMPS TO FLOW IN THE GROUND INSTEAD OF THE NEUTRAL??????????????
LISTEN
If you short Ground to Neutral BEFORE the current flows through the GFI's Torroidal Coil THAT HAS NO AFFECT because the 22 Milliamps flowing out the hot is still returned by the Neutral BEFORE it may be split between Ground and Neutral where you make the jump/short.
It looks to me like if you jump the GFCI's Ground terminal with the GFCI's Neutral terminal on its INPUT (NOT the download downstream feeder) that short is BEFORE any current flows through the GFCI's Torroidal Coil, so the Neutral that's flowing through the sensing coil still sees all that's coming out the hot AND THAT SHOULDNT BE THE CAUSE OF A TRIP.
HOWEVER if the short (Neutral to Ground) is AFTER current flows through the Torroidal Coil, SUCH AS IF YOU SHORT THE DOWNSTREAM OUTPUT TERMINAL ON THE GFCI TO GROUND, then theres a parallel current path for that 22 milliamps of return current so the Neutral current (through torroidal coil) could possibly be 5 milliamps different then the hot current AND IF SO (IM NOT saying yes or no) THE GFCI COULD TRIP.
SUMMARY OF WHAT IM SAYING
If you short Neutral to Ground BEFORE Neutral current flows through the GFCI's torroidal coil THAT DONT AFFECT OR TRIP THE GFCI because all current out the hot (through the sensing coil) still gets returned by the Neutral (through the sensing coil) and theres NO IMBALANCE, NO TRIP.
If you short Ground to the Neutral output terminal that's downstream (current has flowed through sensing coil) and if 22 milliamps is flowing THAT CAN TRIP THE GFCI.
NOW LETS TALK ABOUT A VOLTAGE DIFFERENCE IN NEUTRAL TO GROUND AND ITS AFFECT
At the main panel Neutral is bonded to Ground so you can se there's sure NOT much voltage difference between those two wires there......
Okay as the wires run out from the panel, due to capacitance, and they are BOTH running in parallel with the hot, the voltage on the ground can be higher then mother earth for sure since the earth bond is way back at the panel HOWEVER HOWEVER HOWEVER since Hot and Neutral are BOTH in parallel with the Hot and BOTH are the same length and near same capacitance to hot, the voltage difference between the Neutral and Ground can sure be somewhat different BUT IT AINT MUCH and so little it would take an electrostatic high quality voltmeter (IE extreme high input impedance) to even measure it.
CONCLUSION I just dont envision enough voltage and enough energy difference between hot and ground to cause a 5 milliamp current draw enough to trip a GFCI BUT THATS NOTTTTTTTT BASED ON ANY CALCULATIONS OR ACTUAL MEASUREMENTS OR DATA WHATSOEVER SO NO FREAKING WARRANTY. If you have actual verifiable data to prove theres enough voltage and enough energy between Neutral and Ground to cause a 5 milliamp current flow THEN WHAT I ENVISIONED IS WRONG AS RAIN AND NO PROBLEM. I HAVE NO data, so if you have some and some sound engineering proof I will certainly believe it IE show and prove theres enough of a voltage difference and enough energy between hot and neutral to cause a 5 milliamp current flow....
NUFF SAID it got so deep I sort of lost interest already lol and am not gonna spend much more time on it, I may be right or wrong, it don't matter much..........but it takes some real data and measurements and not guesses or speculation which is what a lot of the above is, as I have no real data OTHER THEN I believe it takes 5 Milliamps of current difference between Hot and Neutral passing through the GFCI's Torroidal Coil to trip it I THINK AT LEAST THAT PARTS RIGHT!!!
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