GFI Trips on shore power

[cricco]

I’m literally at wits end. After being forced to pay $16k for my nightmare blown engine in Virginia, I thought all was well with my 2006 Monaco Monarch. However, I’m getting everything ready to dewinterize, and take our first short trip, when the refrigerator starts beeping at me. I discovered that the bathroom GFI was tripped. After further experimenting, my bathroom GFI keeps tripping on shore power, but works fine on generator. I currently have it plugged in at home, where we have a 30 AMP shore line for the RV. My house wiring is not the issue. This only happens with shore power. I doubt it’s the GFI outlet, as my 50 AMP generator doesn’t trip it. Can anyone help me with this problem?

[road-runner]

houstonstroker wrote:
It appears that he was plugged at home before his trip. If his home outlet is GFCI then that may be the problem. I have found that GFCI RVs do not like to be plugged into GFCI shore power (home). They do not play well together.

Just as a data point, I've had 2 different GFCI RVs plugged into GFCI shore power for over 15 years with zero trips.

[ktmrfs]

houstonstroker wrote:
It appears that he was plugged at home before his trip. If his home outlet is GFCI then that may be the problem. I have found that GFCI RVs do not like to be plugged into GFCI shore power (home). They do not play well together.

my 30A home outlet is on a GFI and it doesn't give any problems with the downstream GFI in the trailer.

Now if you have a GFI on the home outlet AND somehow there is a ground/neutral bond in the trailer I suspect the home GFI will trip since the newer ones (last 5 years at least) will also trip if they detect a ground/neutral short.

[houstonstroker]

It appears that he was plugged at home before his trip. If his home outlet is GFCI then that may be the problem. I have found that GFCI RVs do not like to be plugged into GFCI shore power (home). They do not play well together.

[2chiefsRus]

maybe the original poster just doesn't run the ice maker when dry camping and using the generator.

[CA_Traveler]

ktmrsf, Good explanation but I suspect that the OPs Class A MH has a built in gen that has its neutral and ground bonded.

Check for leakage between the shore plug and ATS. Or possibly the gen voltage or it's waveform is different enough that the GFCI doesn't detect leakage with the gen.

GFCI's do fail and replacement can be a simple solution. Just be sure to use one that is compatible with the alternator and gen if they specs a certain GFCI.

Replacing the ice maker may also solve the problem. I'd certainly use an extension cord from the ice maker to several different 20A GFCI shore plugs to see if it by itself trips the GFCI.

Updated compatibility to include the alternator.

[ktmrfs]

cricco wrote:
Thank GOD! I figured out the culprit! I unplugged the ice maker, and everything seems good now. I guess I can survive without campground water ice.

I suspect that the ice maker has a leakage path to ground. Now why does it trip the GFI on shore power but not a generator?

A GFI will trip when it detects an imbalance in current between the hot and neutral lines of a circuit OR a ground/neutral short.

OK, now lets see how that comes into play on a generator vs shore power.

On shore power the trailer has a path back to the panel where ground and neutral are bonded. So, if there is a path for current to go from hot to a ground, wherever it may be in the ice maker. The GFI sees the current imbalance and trips.

Now how about the generator? Well most generators do NOT tie neutral and ground together anywhere. Nor does your trailer. Now the trailer is on rubber tires maybe stab jacks to the ground and the generator unless it is onboard is sitting somewhere with a likely very high resistance to actual earth or the trailer. So...... there is NO (well not enough) of a leakage path for current to flow except between the hot to neutral through the load. Hence GFI won't trip. put a ground/neutral bond on the generator and repeat and good chance it will trip.

Here is an interesting experiment you can do on your trailer GFI circuit. Power the trailer from a generator with NO neutral/ground bond. If the trailer is wired to code the trailer also has no ground/neutral bond. Now power up the trailer from the generator, don't connect the external ground on the generator to anything. Go into the trailer with a circuit checker with a GFI tester. Push the GFI test button when plugged downstream of the GFI outlet. Won't trip the GFI. Why? The GFI tester will put a path between hot and ground that should be sufficient to trip the GFI simulating a "ground fault". But there is no path from ground back to the hot to complete the circuit. Hence it doesn't trip. all the current still flows from hot to neutral.

Now plug into shore power and repeat. GFI will trip if working correctly. Now Neutral and ground are bonded together at the panel and there is a low resitance path such that a leakage path develops shunting enough current away from the neutral to trip the GFI.

Given this operation there are conditions where a GFI will NOT trip and can cause electrocution. An example is if you were to be wearing highly insulated shoes, on a reasonably insulated surface and put one hand on the hot side of a outlet and the other on the neutral. ALL the current will flow through you and none through any other path to ground. No GFI trip.... could be death.

In most cases most of the current will flow through you from hot to neutral, but some will travel through another path, like your legs to complete a path back to the panel neutral and ground. The GFI will sense this small current imbalance between hot and neutral and trip in a few cycles of 60 Hz, saving you.

[cricco]

Thank GOD! I figured out the culprit! I unplugged the ice maker, and everything seems good now. I guess I can survive without campground water ice.