Open Ground question

[DBECHEN]

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.

[enblethen]

Turning off breakers or on will not show a GFCI issue as breakers do not open ground or neutral leads. You must physically open that portion of the system. Problem could be any where in the 120 volt AC system.
Refer, water heater equipped with 120 volt AC element or converter would be places to start.

[myredracer]

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.

ScottG wrote:

Oddly, GFCI is not required by NEC for a "Trailer" 30A supply or even a RV 50A outlet.

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.

[ktmrfs]

Harvard wrote:
For the record, DC resistance readings will not detect stray capacitance leakage current (AC leakage).

correct, nor will it catch an inductive path to ground from a motor.

And motors are notoreous for tripping a GFI. That is why NEC does not require that certain kitchen circuits have a GFI. For example a fridge or freezer does not need to be on a GFI, so you can put a GFI outlet downstream of the fridge for the other kitchen outlets. Don't want to go on vacation and discover the fridge or freezer tripped the GFI and spoiled the food.

However often a resistance in the 10's or 100's of Kohms is an indicator of a AC leakage path through something that normally is a very high resistance.

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[DBECHEN]

enblethen wrote:
It does not take much o trip a GFCI receptacle.
OP: try unplugging your 120 volt cord powering your refer. Grounded heating element is a common item that goes bad and can trip GFCI.
Is the PI unit hardwired or does it have plug and receptacles. If it is plug and receptacle by-pass the unit. If it is hardwired and you have some experience wirte around the unit.

The PI is hard wired into the rig. I will start with the fridge and work from there. Thanks for a solid starting point.

[DBECHEN]

ktmrfs wrote:
If you have access to an DVM, measure the resistance between the neutral and ground on your trailer plug. It should read in the megohms. If it reads a few ohms, say 10 or less you have a ground neutral bond in the trailer. this is a NO NO. it is against NEC code, and it WILL trip an upstream GFI even if ALL the breakers in the trailer are turned off.

If it reads in the Kohms, but less than about 1 Megohm, you likely have some circuit with leakage to ground. again that can likely trip the GFI and you need to find the source of the leakage.

Since you said the OP installed the surge protector I would carefully check the surge protector wiring and any wiring in the trailer panel for any ground/neutral connection.

If resistance is in the meghom range, do as I previously suggested. turn off all breakers, plug into a GFI outlet, then turn on the 30A. if no trip, then turn on the other breakers one at a time till you trip. only have the 30A and ONE breaker on at a time.

And BTW, the electrician at the storage place is not much of an electrician. If he was he would know that an open ground will NOT trip a GFI. GFI's work just fine on circuits with NO ground. they still protect you and will not trip on an open ground.

In fact,other than checking for a ground/neutral short, a GFI does not even look at current in the ground lead. It looks for a difference between hot and neutral current. If there is a difference, that means there is current flowing in another circuit, like through your body, back to the voltage source.

Thanks for the areas to look at first it should cut down on the time searching for the problem.

[Harvard]

For the record, DC resistance readings will not detect stray capacitance leakage current (AC leakage).

[ktmrfs]

If you have access to an DVM, measure the resistance between the neutral and ground on your trailer plug. It should read in the megohms. If it reads a few ohms, say 10 or less you have a ground neutral bond in the trailer. this is a NO NO. it is against NEC code, and it WILL trip an upstream GFI even if ALL the breakers in the trailer are turned off.

If it reads in the Kohms, but less than about 1 Megohm, you likely have some circuit with leakage to ground. again that can likely trip the GFI and you need to find the source of the leakage.

Since you said the OP installed the surge protector I would carefully check the surge protector wiring and any wiring in the trailer panel for any ground/neutral connection.

If resistance is in the meghom range, do as I previously suggested. turn off all breakers, plug into a GFI outlet, then turn on the 30A. if no trip, then turn on the other breakers one at a time till you trip. only have the 30A and ONE breaker on at a time.

And BTW, the electrician at the storage place is not much of an electrician. If he was he would know that an open ground will NOT trip a GFI. GFI's work just fine on circuits with NO ground. they still protect you and will not trip on an open ground.

In fact,other than checking for a ground/neutral short, a GFI does not even look at current in the ground lead. It looks for a difference between hot and neutral current. If there is a difference, that means there is current flowing in another circuit, like through your body, back to the voltage source.

[enblethen]

It does not take much o trip a GFCI receptacle.
OP: try unplugging your 120 volt cord powering your refer. Grounded heating element is a common item that goes bad and can trip GFCI.
Is the PI unit hardwired or does it have plug and receptacles. If it is plug and receptacle by-pass the unit. If it is hardwired and you have some experience wirte around the unit.

[Hank_MI]

Listen to ScottG and ktmrfs. Disregard Tom/Barbs incorrect and misleading info as he/she obviously doesn't understand how a GFCI works and what it's intended to protect against. Based on his/her statements there would be no need for a GFCI at all as any issue that causes a GFCI to trip would also trip the breaker. Hopefully you all agree that that is just not true.

[DBECHEN]

ScottG wrote:

ktmrfs wrote:

Tom/Barb wrote:

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.

You do not tell us what Amperage you are plugged into at the storage facility.

GFI protection is very rare for 30 AMP circuits So, I'd assume you are reduced to a lower amperage circuit like 15 AMP or maybe a 25 AMP circuit.

And your Surge protector may be having a problem with it.

120V 30A GFI breakers are not very rare at all. maybe not many installed, but even lowes and home depot have them on the shelf. I had not trouble at all getting one when I installed a 120V 30A circuit for trailer power.

Oddly, GFCI is not required by NEC for a "Trailer" 30A supply or even a RV 50A outlet.

At the storage facility it is plugged into a 120V 25AMP circuit. At home into a 30A non-GF I outlet.

[ktmrfs]

ScottG wrote:

ktmrfs wrote:

Tom/Barb wrote:

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.

You do not tell us what Amperage you are plugged into at the storage facility.

GFI protection is very rare for 30 AMP circuits So, I'd assume you are reduced to a lower amperage circuit like 15 AMP or maybe a 25 AMP circuit.

And your Surge protector may be having a problem with it.

120V 30A GFI breakers are not very rare at all. maybe not many installed, but even lowes and home depot have them on the shelf. I had not trouble at all getting one when I installed a 120V 30A circuit for trailer power.

Oddly, GFCI is not required by NEC for a "Trailer" 30A supply or even a RV 50A outlet.

yes it is odd, since any other outside outlet, hot tub, water fountain etc. IIRC requires a GFI Circuit. and a 30A/50A circuit definitely goes to something outside.

But I put one on anyway. better safe than sorry.

[ktmrfs]

Tom/Barb wrote:

ktmrfs wrote:


only if the house circuit is on a GFI. and in most houses GFI is on outside circuits, bathroom circuits, and kitchen circuits. a garage circuit usually is not on a GFI, so make sure you plug into a GFI Circuit.

All house circuits are on breakers, If there is a short in the trailer it will pop the breaker.

we know where the GFIs are required.

from the OP, an OVERLOAD is NOT the problem. He does NOT have a short. he does NOT trip breakers elswhere. His problem is leakage current. A house breaker that is NOT GFI will NOT help him trace down the problem.

[ScottG]

ktmrfs wrote:

Tom/Barb wrote:

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.

You do not tell us what Amperage you are plugged into at the storage facility.

GFI protection is very rare for 30 AMP circuits So, I'd assume you are reduced to a lower amperage circuit like 15 AMP or maybe a 25 AMP circuit.

And your Surge protector may be having a problem with it.

120V 30A GFI breakers are not very rare at all. maybe not many installed, but even lowes and home depot have them on the shelf. I had not trouble at all getting one when I installed a 120V 30A circuit for trailer power.

Oddly, GFCI is not required by NEC for a "Trailer" 30A supply or even a RV 50A outlet.

[ktmrfs]

Tom/Barb wrote:

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.

You do not tell us what Amperage you are plugged into at the storage facility.

GFI protection is very rare for 30 AMP circuits So, I'd assume you are reduced to a lower amperage circuit like 15 AMP or maybe a 25 AMP circuit.

And your Surge protector may be having a problem with it.

120V 30A GFI breakers are not very rare at all. maybe not many installed, but even lowes and home depot have them on the shelf. I had not trouble at all getting one when I installed a 120V 30A circuit for trailer power.