gfci

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Re: gfci

Triphase, given the new requirements in 2005, I have adjusted accordingly: If the washer receptacle is within 6' of the sink, I install it higher, so that it can be seen in the event it trips.

Better still, if there is more than one outlet for the laundry, I install the GFI in the other receptacle outlet available, whether it's within 6' or not, and load-side the washer outlet. Then the receptacle can drop a bit and be less of an eyesore. ;)
 
Re: gfci

triphase wrote:
"the washer motor can trip the gfi. ..What to do?????
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If a load trips a GFCI, qualified persons can briefly isolate the ground prong with a cheater plug, and hook up a Wiggy (G-N), before watching the inrush.

If you can't watch, and Wiggy can trip GFCI (H-G), then (G-G) during a fault can also trip GFCI. IMO Wiggy's are less likely to smoke with series-connected leads, but won't show volts without current, like digital meters (DMM) do.

Normally, a DMM potential 0-2vac common-mode voltage (G-N) exists on parellel-connected loads, but showing > 5mA between ground & neutral (G-N), or activating the solenoid on a Wiggy is not normal.

Maybe a series/dedicated-circuit EGC normally shows more of this CMV anomaly, but metering the isolated Gnd-prong (G-N) or (G-G) will only test the appliance leakage, on both circuit types; DMM w/no load, then Wiggy w/load.

If a cheater-plugged appliance is faulty, running or not, even a qualified person can be electrocuted by touching it. So, be careful. :(

[ January 10, 2006, 03:35 AM: Message edited by: ramsy ]
 
Re: gfci

OK, OK ! Your killin' Me again. I have had numerous problems, gfi tripping when motors start up refrige, freezers, washers, etc. (can I use lock rotor) Oh, by the way not my installs just troubleshooting and yes did load checks and all appliances are new so are buildings???????? Help!!!!!!!!!!!!!!!
 
Re: gfci

OK, OK ! Your killin' Me again. I have had numerous problems, gfi tripping when motors start up refrige, freezers, washers, etc.
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Me too. :D

I've had a terible time trying to convince some of the people on this forum that such a thing is even possible. :D

Here's the thing though. After giving this a lot of thought I've finally decided that the GFI is actually responding as it's intended. There is actually current "leaking", or not returning through ground.

Edit: Did I say ground? :eek: I meant neutral.

[ January 10, 2006, 10:36 PM: Message edited by: physis ]
 
Re: gfci

physis wrote:
..GFI is actually responding as it's intended. There is actually current "leaking"
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Can the objectional current be found by metering a lifted plumping bond at the panel?

Phantom grounds may leak current through structural bonds.

After load testing a ~1.7 ohm path through EGC's, with two wires behind the wall in non-metalic cable, I had to remove all cord-connected appliances on the circuit before the phantom ground disappeared.

A window-AC cord ground prong, shorted (DVM ~1 ohm) to the steel window frame, to branch neutral was found on all window frames in the house; perhaps bonded to plumbing. Service meter lock prevented opening panel to lift plumbing bond.

I suppose this phantom-ground confusion may be common when motor circuits, case-housing bonded to building structures, share the same circuits? NEC 430.12(E),430.145(C)
 
Re: gfci

Originally posted by triphase:
OK, OK ! Your killin' Me again. I have had numerous problems, gfi tripping when motors start up refrige, freezers, washers, etc.
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I used to see this from time to time when I did residential work. I always quessed that it had someting to do with a starting capacitor causing the hot to draw amps before the neutral let them go.

Sorry that is not a very technical explaination. :cool:
 
Re: gfci

triphase wrote:
OK, OK ! Your killin' Me ..I have had numerous gfi tripping. Help!!!!!!!!!!!!!!!
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Check the outlets for a Bootleg or false ground, another type of phantom ground. That might offer some capacity for juice to flow thru appliance bonds.

[ January 10, 2006, 08:21 PM: Message edited by: ramsy ]
 
Re: gfci

There is a good explanation to why a GFCI trips from motors loads but the truth is older GFCI's would trip also just because the water fill valved shut off (why the washer is always full when you get the call) :D . Think about it, the current running to the load is only canceled out by the same current returning to the source through the same current coil in the GFCI. Now this current is at 60hz. What happens when any inductive load is turned off?
A high voltage spike happens, this voltage spike can cause a current in one of the two circuit conductors because it is only maybe at 1/4 of the 60hz cycle. This alone would cause a GFCI to trip but newer GFCIs have MOVs and time delays to reduce this problem and have done a good job in the newer GFCI's
I have not had a problem with faulse GFCI triping lately as I use to. :D

[ January 10, 2006, 08:47 PM: Message edited by: hurk27 ]
 
Re: gfci

Hey Wayne, How've ya been.

By Wayne:

the current running to the load is only canceled out by the same current returning to the source through the same current coil in the GFCI. Now this current is at 60hz.
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That's a really interesting thought. But I still have to say the path back is the same.

I have to admit though that I really don't know where this disappearing current's going. It's going somewhere.

Edit:

Can the objectional current be found by metering a lifted plumping bond at the panel?

Phantom grounds may leak current through structural bonds.
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The current you're talking about is probably happening over a few micoseconds to a few milaseconds. It's not gonna be easy to catch.

And as for the phantom concept, it's not a phantom, it's real.

[ January 10, 2006, 10:42 PM: Message edited by: physis ]
 
Re: gfci

Originally posted by triphase:What is MOV?
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From littlefuse.com:
A metal oxide varistor, or MOV, is a voltage dependent, nonlinear device that provides excellent transient voltage suppression. When exposed to high transient voltage, the metal oxide varistor clamps voltage to a safe level. A metal oxide varistor absorbs potentially destructive energy and dissipates it as heat, thus protecting vulnerable circuit components and preventing system damage.
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Re: gfci

Sam
The transient current spike will travel in one direction right through the GFCI, in the other direction it has to travel all the way through the load then to the GFCI. I'm thinking that this slight delay is what causes enough phase shift in the return path that causes the imbalance.
This is also why I think that not all inductive loads cause this problem as some have a much shorter path through the load.

The thinking is the spike is produced when the power switch is opened and the arc jumps accross the contacts allowing the buildup of the higher voltage.
I know I'm not puting this down exactly how I'm thinking but it's close. :D
 
Re: gfci

Wayne,

You only have one current path, therefore you cannot have a phase shift. If you have two currents paths then the GFI will trip.

Most nusiance tripping caused by motors is due to coupling capacitance between L-G and N-G. Some of this capacitance exists between the conductors in the cord and is dependent on the length of the cord and the quality of the internal insulation. Additional capacitance exists between the motor windings and internal mettalic parts. Finally (and maybe the biggest cause) there is the capacitance between the internal plates and the external housing of start and run capacitors, again quality of insulation is a big factor.
 
Re: gfci

physis wrote:(GFCI trip current) is probably happening (too fast). It's not gonna be easy to catch.
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Agreed, that would be hard to catch.

And, bonded window frames are also hard to catch. But, false grounded water heaters, washers, & disposers all put neutral current in contact with water, not considered an insulator.

For gas appliances, a N-G bootleg puts current thru gas lines, and returns an objectionable path to earth or main bondings. Fires might happen this way, perhaps less so w/European two prong appliances.

Bootleg grounds (N-G bond) leak objectionable-neutral current, thru appliance grnd-prong, if a return path exists.

If bad GFCI's are more common than false grounds, changing out the GFCI would be the most common fix.

physis wrote:
And as for the phantom concept, it's not a phantom, it's real.
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Agreed. Substitute "phantom" with "hidden" where applicable.
 
Re: gfci

Jim wrote: You only have one current path, therefore you cannot have a phase shift. If you have two current paths then the GFI will trip.
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Could Wayne's inductive kickback idea work on a shared neutral, with the extra path? But, then would any circuit imbalance trip GFCI's on shared neutrals?

Jim wrote: ..capacitance exists between the conductors ..between motor windings ..between internal plates and external housing (of) capacitors
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Capacitance is not objectionable current, but maybe enough momentary current to trip GFCI's with false grounded EGC to neutral; especially on outlets surving motor appliances.

[ January 11, 2006, 11:12 PM: Message edited by: ramsy ]
 
Re: gfci

Ok jim you beat me to it. I cheated by editing that post.

Shared neutral it is. Where do we send the check.
 
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