Defeating GFI

[Sean]

If the GFCI in question is working properly, then any ground-neutral fault in the coach would trip it instantly.  The fact that it is not tripping instantly means that either it is inoperative, or else you don't really have such a fault in your coach.  Step one here would be to test the GFCI.  The self-test button is unreliable; instead, purchase a GFCI tester -- this is one of those little three-light testers that also tell you if the outlet is properly wired, except that it also has a little button you press to test the GFCI.  Available at Home Depot and elsewhere, they are maybe $15.  Handy to have, because you can never tell when a plain-looking outlet might be wired downstream of a GFCI, and this lets you know right away.

Now, having said all of that, my experience is that GFCI outlets that nuisance-trip after a period of time (as opposed to when you first plug in) are also defective.  One common issue is moisture in the J-box, which can become just conductive enough to cause a trickle current between either the hot or the neutral and the ground.  When you think about it, moisture is exactly one of the reasons GFCI outlets are so important in the first place.

If your coach is tripping this one outlet consistently after a period of time, I would not implicate the coach itself unless is also does that consistently to other GFCI outlets.  If you can't find another outlet nearby to test, then drop the $20 and replace your host's receptacle for him, and see if the problem goes away.  We carried a spare GFCI with us for exactly this reason.  (We also carried spare 50- and 30-amp breakers for defective campground pedestals, along with spare receptacles.  When you get the last good spot at that remote state park, it's easier to just fix the dang pedestal than to move or try to get rangers or volunteer hosts to do anything about it.)

HTH,

-Sean

[wagwar]

It does not trip instantly, until I flip one of my breakers in the bus on (eg entry door receptacle). Recall that I have all of my breakers off. With all breakers off the gfi will pop after a few minutes of charging- even at a low 5a level. If I flip a breaker on, that will cause it to pop immediately. So, still not able to definitively rule out neutral ground bond or ground fault problem.

[wagwar]

Btw, I can confirm that neutral and ground are not bonded in main panel, so if it is a neutral ground bond problem, it is not happening at my main panel.

[robertglines1]

Pro already been mentioned--Grounds bonded within some appliance.  Been there on that one.

[Seangie]

Dave (wagwar) -

How did you make out?  Any progress?

-Sean

[wagwar]

Not really. I swapped out the gfi for standard rec. temporarily. I need to thoroughly test the neutral ground bond for proper operation, but I just don't know how to go about it. 
 
The tests that Sean outlined in the previous thread that I linked to in a previous response seem to check out ok. So I'm not sure where to go from here. I think i may still have a problem.

[Lin]

Just a question.  Would using one of those little 3 prong to 2 prong adaptors have worked since it cuts out the ground?

[bobofthenorth]

Just a question.  Would using one of those little 3 prong to 2 prong adaptors have worked since it cuts out the ground?

Sometimes. Yes. But. ........

If the ground fault is a connection between the ground and neutral (green/white) on the coach then the 3 to 2 adapter will let you hook up.  Whatever you have for a ground fault still exists - you've just masked its effect.

If the ground fault is an alternative path to ground - ie. not through the green wire - then the 3 to 2 adapter won't change anything. 

I can think of situations where the 3:2 adapter might be an acceptable risk --  FOR ME --- but I can also remember homes that were wired with only 2 conductors.  We don't do that anymore either.

Ultimately this comes in the category of "if you have to ask the question then you shouldn't try it at home".

[Jriddle]

Sometimes. Yes. But. ........

If the ground fault is a connection between the ground and neutral (green/white) on the coach then the 3 to 2 adapter will let you hook up.  Whatever you have for a ground fault still exists - you've just masked its effect.

If the ground fault is an alternative path to ground - ie. not through the green wire - then the 3 to 2 adapter won't change anything. 

I can think of situations where the 3:2 adapter might be an acceptable risk --  FOR ME --- but I can also remember homes that were wired with only 2 conductors.  We don't do that anymore either.

Ultimately this comes in the category of "if you have to ask the question then you shouldn't try it at home".

I remember living in a trailer house that was wired by a friend. Every time it rained we would get shocked when the door  was opened from the outside. I guess we are lucky to be around to tell the story. You must ensure you don't become the ground for a ground fault. I guess at that time nothing would hurt me LOL. Young dump and ______?

John

[wagwar]

REVISIT of the GFI Problem:

We are visiting our friends Howard and Ellen. Howard and I ran down the ground fault interrupt problem on this thread to an auxiliary Makita air compressor I had plugged into a GFI in the engine bay. After extensive testing, we discovered that unplugging the air compressor from the outlet, the GFI shore connection quit dropping. So apparently if I need to use a GFI outlet, I just need to unplug the air compressor. Perhaps the ground and neutral are bonded inside the compressor? I can't say. However at that point, we also had the Trace SW4024 inverter disconnected.

So then we reconnected the Trace SW4024 inverter. I had the inverter Off when we reconnected to the GFI. The power conditioner accepts the power. The auto transfer switch accepts the power and the main AC panel breakers are all ON. The GFI did not trip and I had power in the coach.

So I have no reason to believe that I have either a ground fault OR a problem with the neutral-ground bond inside the bus. 

So then I turn on the inverter and a minute or so later, the GFI kicks out.

We checked the wiring into and out of the inverter, the automatic transfer switch and the breaker for inverter input and there is no obvious problem with the wiring. We have eliminated any ground faults or neutral-ground bonding issues in the main bus panel.

Still, I cannot connect to a GFI outlet with the inverter ON. If I leave the inverter Off, I have no problem. As soon as I turn the inverter ON - whether it is ON (inverting) or ON (Charge only) the GFI kicks out. I have also tried (as Sean Welsh suggested) to remove the spade connector inside the invertor for the ground relay connection. It makes no difference.

Any suggestions?

[Geoff]

I just skipped through 3 pages of advice to give you my simple solution since I have the same setup--

I have a separate 40amp 3- stage 120v batery charger (plugged into the GFI) with 12v alligator clips I use in this situation.  The house batteries stay charged for low usage of the inverter. 

I also used to trip the GFI, this is how I got around that.

--Geoff

[wagwar]

Outcome:
Sean and Robertglines called it right. After 2 days of testing and running down circuits from the house thru the ATS, Inverter and EMS, here's what it came down to:

1. The 120 vac Makita air compressor that was plugged into a GFI in the engine bay was causing a ground fault at the shore pedestal GFI. I suppose the ground and neutral are bonded within the appliance, simply unplugging it from the receptacle resolved that issue.

2. There was an additional ground fault occurring whenever the inverter was turned on. That turned out to be a weak GFI receptacle in the shore pedestal. A different GFI receptacle worked fine.

So, as it turns out there were no neutral-ground bond or ground faults within the bus wiring itself. I'm glad to know that.

Thanks to all of you who responded. This is a great resource.

Jim