Tripping a GFI power source?

Bram

Member
Why would my trailer all of a sudden start tripping my GFI circut in the shop? The trailer is 2 yrs old and just started doing it last week. I've tried 2 different GFI circuts and 2 different shore power cords. Even with all AC breakers off it still trips. Everything works fine on the generator and RV park power. Any thoughts?
 

jnbhobe

Well-known member
Check your breaker box for a loose neutral (white wire) or a loose ground (bare or green wire)
 

Willym

Well-known member
GFI's work by comparing the current in the hot side of the circuit with that of the neutral side. If the difference exceeds a certain amount then the circuit is tripped. I don't think that poor connections should cause a GFI trip. However, if you have some current leakage between the hot side and ground between your trailer connector and the circuit box busbars the GFI will trip, even if all the circuit breakers are open. You may have a small physical short causing this, or some water ingress. I'd start by removing the circuit breaker panel cover and looking in there. After that, check the connector on the side of the trailer.
 

jbeletti

Well-known member
My standard answer in this situation - check to see if your electric heating element in the water heater is switched on. If it is, you may have blown the element. Had it happen in a TT I had in 2004. It kept tripping the campgrounds 30 amp GFI breaker.

Jim
 

Bob&Patty

Founders of SoCal Chapter
JB, thanks for the tip. Never thought about the "OL water heater heating element" trick.
 

Bram

Member
Thanks to all for your inputs. I'v been out of town for a few days so I think I'll dive into the AC power panel this weekend and see what I can find. This is definitely a GFI trip and not an amperage overload trip. Jim, the hot water heater element is fine as we used it last weekend at Wine Country RV. Worst case is I will have to put in a non GFI circuit in the shop just for the trailer.
 

branson4020

Icantre Member
Bram,

As I posted before, If everything works when plugged into a non-GFCI outlet, but trips a GFCI outlet, then there is a short between neutral and ground somewhere. Could be at some outlet in the coach, could be in the cord, or transfer switch or ??? - you just have to trace it down.
 

Bram

Member
Thanks again.

I did isolate the problem to the Ceiling fan circuit. With either of the common or ground disconnected it won't trip. I removed the fan and and ceiling shroud and pulled the electrical panel to see if the romex was cut, pinched or stapled for the portions that I could get to. Nothing was out of the ordinary. This means there is a ground/common short somewhere in the wall/ceiling that I can't get to. I think my option is to just leave the ground disconnected at the electrical panel. Wadaya think?
 

branson4020

Icantre Member
Did you put a meter across the disconnected neutral and ground wires to see if there was a short? Could it be in the ceiling fan itself?
 

Bram

Member
Yea, I had the fan completely removed with all three wires open ended, still tripped. Yes there is continuity between the common and ground wires at the electrical panel.
 

hoefler

Well-known member
Continuity between ground and common is normal in all residential wiring. The utility has them connected at the transformer. Your meter base has them connected. And most breaker boxes have them connected as well. A GFIC breaker monitors voltage from hot to common, and has no connection to ground.

Turn off the breaker to the fan, check if GFIC still trips. If not, it is in that circuit, chances have a pinched wire.
 

branson4020

Icantre Member
Continuity between ground and common is normal in all residential wiring. The utility has them connected at the transformer. Your meter base has them connected. And most breaker boxes have them connected as well. A GFIC breaker monitors voltage from hot to common, and has no connection to ground.

Turn off the breaker to the fan, check if GFIC still trips. If not, it is in that circuit, chances have a pinched wire.

Nope, your RV main panel does NOT have neutral and ground bonded. If you are not connected to shore power, there should not be any continuity between neutral and ground.
 

hoefler

Well-known member
Check the outlet in the pedestal you plug into. When plugged into shore power you will have continuity.
 

branson4020

Icantre Member
Check the outlet in the pedestal you plug into. When plugged into shore power you will have continuity.

I agree. Neutral and ground are bonded at the main service panel that feeds that pedestal. They should also be bonded at any power source, like a generator or inverter. But, if you UNPLUG your coach from shore power and check the end of your power cord, you should see no continuity between neutral and ground.
 

hoefler

Well-known member
I agree. Neutral and ground are bonded at the main service panel that feeds that pedestal. They should also be bonded at any power source, like a generator or inverter. But, if you UNPLUG your coach from shore power and check the end of your power cord, you should see no continuity between neutral and ground.

True, but you trip the GFI when you are plugged in, not disconnected.
 

branson4020

Icantre Member
True, but you trip the GFI when you are plugged in, not disconnected.

Yes, exactly. The symptom is that the pedestal (well, garage) GFI trips, but no circuit breaker trips and he can plug into a non-GFI pedestal and everything works. The reason is because the GFCI trips when it senses a current imbalance between whats flowing in the hot and neutral legs. If there is a connection between neutral and ground on the coach side of the GFCI, it creates a path for current to flow around the GFCI. The current will split between the neutral and ground paths, creating an imbalnce that will trip the GFCI.
 

hoefler

Well-known member
But the GFI has nothing to do with the ground wire. GFI's monitor the hot and common only. Look at a GFI breaker, it has the hot lead and the common wire from that circuit hooked to it, no ground monitoring. Think about this, most house hold appliances have 2 prong polarized plugs, no grounds. If a GFI monitors currant going to ground, it would be useless for hair dryers and curling irons being used in the bath room.
 
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