Trips GFCI

[Richard and Rhonda]

OK, I know others of you have coaches that trip ground fault circuits when plugged into 110. Others of you say you don't have this problem.

Does anyone know why? and better yet what specifically to change to fix that.

[RussWhite]

Richard,

I am going to assume you are referring to the GFI external to the coach that you have plugged the coach into. Hope that is a good assumption as I am going to ramble on about that.

First a quick review of how a GFCI works.
Copied from Hot Stuff Works - When you look at a normal 120-volt outlet in the United States, there are two vertical slots and then a round hole centered below them. The left slot is slightly larger than the right. The left slot is called "neutral," the right slot is called "hot" and the hole below them is called "ground." If an appliance is working properly, all electricity that the appliance uses will flow from hot to neutral. A GFCI monitors the amount of current flowing from hot to neutral. If there is any imbalance, it trips the circuit. It is able to sense a mismatch as small as 4 or 5 milliamps, and it can react as quickly as one-thirtieth of a second.

So if there exists any leakage path from the "hot" phase to ground ( not neutral ) the GFCI is just going to do its job and trip. Remember, the idea of the GFCI was never to power a coach, but to supply power to an individual device and protect the use of that device from becoming part of the leakage path from hot to ground. Your coach would have to have all circuits and appliances in perfect condition ( no leakage paths ) for the GFCI not to trip. If this happened to me I would start by opening all the circuit breakers in the AC distribution panel and crossing my fingers the GFCI did not trip then. If it does it will be a wiring leakage between the plug and the AC panel and probably not easy to find. If it does not trip, then just start closing the breakers one at a time until you find the offending circuit.

Good luck.
Russ

[encantotom]

i know as people have stayed at my place with their newells, every one of them tripped the breaker on my house. if i remember right, the zonkers, days and hockwald's all did.

however, mine has never done it. i attributed it to the EMS (electrical management system) that my coach has on it. it monitors incoming curretn, voltage and freq and polarity and will shut the coach off if any of them are out of spec and if there is a surge. somehow that system protects mine from tripping.

i also think that the way the neutrals are done on the coach has something to do with it.

i will call my son-in-law tomorrow and get his expert advice. he has a phd in power engineering and works for the power company.

tom

[chockwald]

Correction, the Hockwald's not only did not trip the breaker, we were able to run our front A/C (only draws 10amps) without tripping it!

[encantotom]

i did say....if i remember.....

tom

[RussWhite]

Tom's comment about the neutral got me to considering the possibilities. While I don't agree that the EMS has any bearing on tripping how the neutral is handled in the distribution panel sure does. Just remember that for a GFCI not to trip, ALL the current that flows through the hot wire MUST return through the neutral. Now if an owner or a manufacturer bonded the neutral to the ground in the distribution panel that GFCI will trip every time. Most distribution boxes allow for this configuration and it is easy to do. Some even have a screw that is positioned between the neutral and ground buss, and just screwing it in bonds the two systems together - something you do not want to do on an RV. Here is a bit of an explanation from a primer on RV electricity.
First thing first: The neutral and ground in an RV electrical loadcenter are NOT to be bonded together.
The RV chassis is isolated from ground by definition. Metal leveling jacks and such, mounted on the vehicle frame do not make an adequate ground contact. Therefore, in an RV, you always want to have a "floating" neutral, where the neutral and vehicle ground never come together. When you bond the neutral and ground together in an RV, you have a "floating" ground (rather than neutral) and this will result in nutty things happening.

My comment - and one of the "nutty" things will be a GFCI tripping if you try to power the RV through one. So check it out if your coach trips Tom's breaker. Mine did not as I don't remember plugging it in there:D

[Richard and Rhonda]

OK,

I have turned off all the breakers in the internal panel before and the GFI still trips.

Russ, if I interpret your post correctly then I should be able to ohm between ground and neutral. If it is open then that is not the problem. If ground to neutral is not open then that is the place to start looking.

[RussWhite]

Yes - and I had intended to suggest checking resistance between neutral and ground with the coach unplugged. You want a very high reading. Russ

[davidmbrady]

Richard,

Does your bus use a Reverse Polarity Indicator by PMMI? If so, they've been known to trip GFCI's. They can be fixed by swapping the internal resistor. I'll give you more info if you need it. (The upload file size limitation is preventing me from uploading a PMMI doc on the topic).

David Brady
'02 BlueBird LXi

[Richard and Rhonda]

David, YES !!!!! Most of the coaches of my era had that setup by PMMI for the reverse polarity indicator.

I thought I had read about the PMMI issue many years ago on the Bluebird forum.

I tried to contact PMMI but never got a call back.

Could you email me the info richard.entrekinATalconlabs.com?

[davidmbrady]

Hi Richard, It's on its way. Good luck.

David Brady
'02 BlueBird LXi