Open Ground question

Tom/Barb wrote:

ScottG wrote:


That's not the case. It trips all the GFCI's at the facility but is ok on a standard 30A (no GFCI).

We do not know all the GFIs at the storage facility are good. they are probably all on the same circuit. and wired wrong.

a cheap tester will eliminate the doubt.

to determine if it is the trailer, simply read continuity between the two hot leads and the common ground on the trailer plug, it should show and open.

If it doesn't show an open circuit, it would pop the 30 amp breaker at home or smoke something.
.

If a GFCI is wired wrong in any way, it will not work (trip) under any circumstances.

Further, a continuity check may very well not reveal the leak. The higher voltage will often cause continuity when low V wont. Think of this as an active short.

Tom/Barb wrote:
...It is easy to determine if it is the trailer. read continuity between the two hot legs and the Common ground of the plug, it should be open to both.

OP has a 30 amp unit, so there will be only one hot leg. The test suggested should still be valid--just between hot, neutral and ground rather than between two hots and ground.

ktmrfs wrote:

open ground will NOT trip a GFI. A GFI is designed to work with a circuit that is not grounded, e.g. the old two prong plug.

there are TWO things that will cause a GFI to trip.

1) unbalanced current between the hot and neutral.
2) ground neutral short. e.g. somewhere downstream the ground and neutral are touching.

now a regular 30A RV circuit most often does NOT have a GFI, so no issue.

couple of things that could be causing an issue.
1) leakage in the fridge 120V element to ground.

one way to check is to turn OFF every breaker in the RV. GFI should Not trip. if it does, the fault is before the 30A main breaker. If no GFI trip, trip each circuit and see which one trips the GFI. whatever circuit trips the GFI tells you which circuit either has excessive leakage current or a ground neutral short.

This is one of the best responses to the question; there are a lot of confused people who seem not to understand what a GFCI detects and what it does not detect.

If you have leakage from hot to ground, shutting off the breakers will help track that down. If there's a short or partial short between neutral and ground, shutting off the breakers will not take that away (they only shut off the hot side) and you're left with the job of hunting it down. These can be rather tricky to find, either in a house or in an RV, but it's a definite safety hazard under certain fault conditions such as an open ground connection and should be corrected.

There is also a small chance that there is sufficient leakage from ordinary noise suppression and other input conditioning circuits on the various electrical devices in the RV which, if taken individually, would not be sufficient to trip the GFCI. This would only affect things with three prong plugs. In most cases it's more productive to assume that this is not the cause and look for other problems.

ScottG wrote:


That's not the case. It trips all the GFCI's at the facility but is ok on a standard 30A (no GFCI).

We do not know all the GFIs at the storage facility are good. they are probably all on the same circuit. and wired wrong.

a cheap tester will eliminate the doubt.

to determine if it is the trailer, simply read continuity between the two hot leads and the common ground on the trailer plug, it should show and open.

If it doesn't show an open circuit, it would pop the 30 amp breaker at home or smoke something.
.

Tom/Barb wrote:

No, it would not because a GFCI fault is not an overload.

His 30 AMP at home would not be a ground fault.

ScottG wrote:

Tom/Barb wrote:

ScottG wrote:
Of course you have an open ground. Your ground isn't supposed to be bonded and none of that matters anyway. A GFCI doesn't trip because of an "open ground".
Somewhere, you have a leakage to ground. Could be a wet outside receptacle, bad fridge heater *even if it works fine) or water heater or even a bad microwave (rare). I would unplug the appliances and see if the fault remains.

If that was his problem, plugging it at home would pop the breaker.

No, it would not because a GFCI fault is not an overload.

OP, another thing that can cause it is a failing converter. I would turn off its breaker and see if it still trips the GFCI.

It is easy to determine if it is the trailer. read continuity between the two hot legs and the Common ground of the plug, it should be open to both.

Tom/Barb wrote:

ScottG wrote:
Of course you have an open ground. Your ground isn't supposed to be bonded and none of that matters anyway. A GFCI doesn't trip because of an "open ground".
Somewhere, you have a leakage to ground. Could be a wet outside receptacle, bad fridge heater *even if it works fine) or water heater or even a bad microwave (rare). I would unplug the appliances and see if the fault remains.

If that was his problem, plugging it at home would pop the breaker.

not unless his breaker at home is a GFI breaker. not real common especially on a 30A 120V circuit. low current leakage to ground does not make a normal breaker trip.

A plug in GFCI tester isn't going to show you anything. The GFCI trips when the RV is plugged in. That in itself proves the gfci will trip which is all the tester will do.
Now if the GFCI wouldn't trip, that's when the little tester would tell you something.

KTMRFS - great info!!

DBECHEN wrote:
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 anything the GFCI trips on the pole. We talked to our storage facility manager and they had an electrician come out and he said the issue was our RV having an open ground. We have a Progressive Industries surge protector that was installed by the first owner. When we plug into the 30 amp plug at our house and in campgrounds there is no problem. Any ideas what may be causing this? Thanks in advance.

open ground will NOT trip a GFI. A GFI is designed to work with a circuit that is not grounded, e.g. the old two prong plug.

there are TWO things that will cause a GFI to trip.

1) unbalanced current between the hot and neutral.
2) ground neutral short. e.g. somewhere downstream the ground and neutral are touching.

now a regular 30A RV circuit most often does NOT have a GFI, so no issue.

couple of things that could be causing an issue.
1) leakage in the fridge 120V element to ground.

one way to check is to turn OFF every breaker in the RV. GFI should Not trip. if it does, the fault is before the 30A main breaker. If no GFI trip, trip each circuit and see which one trips the GFI. whatever circuit trips the GFI tells you which circuit either has excessive leakage current or a ground neutral short.

Tom/Barb wrote:

Tom/Barb wrote:
If it works every where but there, I would suspect there.

there is a cheap little tester for GFI circuits get one and test the storage facility.

It depends upon if the facility is using the white wire as a common ground or if they are using the bare copper to a ground post as the common ground.

TESTER

That would be extremely unlikely and have to be boot-legged. A GFCI would never work (ie trip) on that kind of illegal circuit.