Open Ground question
Hi all, I have been having a problem with plugging into the shore power at our storage facility. They have all circuits run through GFCI outlets on the pole. When we plug in and we are not running any...
Forum Discussion
I'd start by turning off all breakers in the panel. Then turn on the 30 amp main breaker and if the GFCI doesn't trip, that rules out anything related to the shore power cord and panel. Then turn on one branch circuit breaker at a time until the GFCI trips. A defective HWT element is one common cause of tripping a GFCI and may have failed due to turning it on without water in the tank.
If you did happen to have an open ground in the 30 amp supply, the EMS would be shutting you down. You seem to have a leakage to ground somewhere which causes an imbalance in the current in the hot and neutral conductors which the GFCI will sense and trip. A GFCI looks for current on the hot & neutral to sum to zero and trips when the imbalance reaches a min. of 5 milliamps. Below is a simplified drawing of how a GFCI recept. works. You only need a hot and neutral to work. You still could have a leakage to ground with an open ground if the TT had a return path to ground somewhere like maybe via the stab. & tongue jacks. I don't think it's even possible for an RV panel to have the neutral and ground bonded together since they don't come with a bonding screw like in panelboards for building use (and are removable) - unless a factory worker negligently did so somehow. There must always be a contiguous ground conductor all the way back to the building's main service panel.
FWIW, CGs and other facilities sometimes say they have an "electrician" when they are only a glorified maintenance/handyman person. While checking things out, I'd suggest using a receptacle tester to check the polarity of all receptacles and the one you're plugged into. I found 2 recepts. in our TT with reversed polarity.
If you did happen to have an open ground in the 30 amp supply, the EMS would be shutting you down. You seem to have a leakage to ground somewhere which causes an imbalance in the current in the hot and neutral conductors which the GFCI will sense and trip. A GFCI looks for current on the hot & neutral to sum to zero and trips when the imbalance reaches a min. of 5 milliamps. Below is a simplified drawing of how a GFCI recept. works. You only need a hot and neutral to work. You still could have a leakage to ground with an open ground if the TT had a return path to ground somewhere like maybe via the stab. & tongue jacks. I don't think it's even possible for an RV panel to have the neutral and ground bonded together since they don't come with a bonding screw like in panelboards for building use (and are removable) - unless a factory worker negligently did so somehow. There must always be a contiguous ground conductor all the way back to the building's main service panel.
FWIW, CGs and other facilities sometimes say they have an "electrician" when they are only a glorified maintenance/handyman person. While checking things out, I'd suggest using a receptacle tester to check the polarity of all receptacles and the one you're plugged into. I found 2 recepts. in our TT with reversed polarity.
ScottG wrote:I've often wondered about that too. Cost is around $40 retail. When it comes to residences, they now call for GFCIs and AFCIs on just about anything they can think of. The NEC code writers don't seem to pay the attention to the RV world it deserves.
Oddly, GFCI is not required by NEC for a "Trailer" 30A supply or even a RV 50A outlet.
