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Old 07-02-2015, 08:54 AM   #1
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Double GFCI

Have you had this problem?
Just left a park where the 30 Amp service was Ground Fault Circuit Breaker protected. Every time I turned ON the post breaker it tripped a breaker on the RV, causing the post breaker to trip back OFF too. Even a qualified electrician could not get us power.
I tried using a GCFI circuit at my son's house and it trips both OFF too.
Moral: Can't use House or Post GFCI's

Asked why the park had GFCI's on 30A but not on 50A service, Answer, that was code. Park was behind a dam. Only place I ever saw this.
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Old 07-02-2015, 10:08 AM   #2
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Quote:
Originally Posted by Fiesta48 View Post
Have you had this problem?
Just left a park where the 30 Amp service was Ground Fault Circuit Breaker protected. Every time I turned ON the post breaker it tripped a breaker on the RV, causing the post breaker to trip back OFF too. Even a qualified electrician could not get us power.
I tried using a GCFI circuit at my son's house and it trips both OFF too.
Moral: Can't use House or Post GFCI's
Asked why the park had GFCI's on 30A but not on 50A service, Answer, that was code. Park was behind a dam. Only place I ever saw this.
Fiesta48
If you are tripping a pedestal GFCI , (Ground-Fault Circuit Interrupter), you have a "ground fault" in your RV electric cord.... OR somewhere in the coach itself.

To determine if that ground fault is in the cord:
1.) Turn the pedestal breaker off
2.) Unplug both ends your cord
3.) Connect only the pedestal end of your cord to the pedestal.
If the GFCI trips replce the cord.
If it the GFCI doesn't trip the cord is okay....(if does replace the cord).

If the cord is okay:
1.) Turn OFF all of the 120VAC breakers in the main breaker panel of the coach.
2.) Connect the coach to the pedestal via the good cord.
3.) Turn the pedestal circuit breaker ON.
4.) Turn the breaker panel breakers ON one at a time... (when the GFCI trips you have you have found which circuit has the ground fault).
5.) When the GFCI trips unplug, (or disconnect), anything/everything connected to that circuit and reset the GFCI.
6.) Next plug in, (reconnect) things one by one.
7.) When the GFCI trips you have found the culprit.

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Old 07-02-2015, 11:06 AM   #3
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Mel S checklist is very good. If you verify the power cord is good the next step is to add in circuits as he described. I have seen several posts regarding the Norcold 12XX series with an ice maker. For some reason they seem to be subject to leaking to ground. I would start shutting all things down as Mel said and then making it the first device/circuit you put back on line. It solved my problem while waiting for my residential refer to be installed.
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Old 07-02-2015, 11:38 AM   #4
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FWIW I Would be tempted to modify any adapter for plugging a 50 A System into 30 A by tying the safety ground to the neutral at the adapter. That would keep loop currents out of the GFI in the pedestal. That is probably the problem. IF the system is OK on a 50 A pedestal you do not have a Ground Fault in the unit but you may well have currents in the wrong place in an adapter.
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Old 07-03-2015, 11:33 AM   #5
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I agree with mel on this one: there is likely a ground fault on the coach: disconnect everything, and make connections one at a time until you find out where it is.

Quote:
Originally Posted by nothermark View Post
FWIW I Would be tempted to modify any adapter for plugging a 50 A System into 30 A by tying the safety ground to the neutral at the adapter. That would keep loop currents out of the GFI in the pedestal. That is probably the problem.
Actually, I would think that tying the neutral to the ground at the adapter would cause more problems and would make the GFCI trip more often. Adding that connection would create a loop where some of the neutral current from the rig could cross over to the ground, bypass the GFCI, and connect back up with the neutral connection back at the main service entrance breaker panel. With some of the neutral current flowing through the grounding conductor, the GFCI will see an imbalance in the hot and neutral currents, and that will cause it to trip. By connecting neutral and ground at the coach, you would be creating an actual ground fault, the very thing that the GFCI is trying to detect and prevent.

There should be only one connection between the neutral and ground conductors, and that should be at the main service entrance panel and not in the motorhome. That main service entrance panel is back at the campground (or home) where the utility service first enters the property.

Quote:
IF the system is OK on a 50 A pedestal you do not have a Ground Fault in the unit but you may well have currents in the wrong place in an adapter.
I'm not sure how you come to this conclusion. Most (all?) 50 amp pedestals do not have GFCI protection on the 50 amp outlet. Without a GFCI tripping, (or using specialized test instruments to measure a current imbalance in the hot and neutral) how would you know if you have a ground fault problem? It's quite possible that there could be a ground fault in the coach, and you'd never know it using a 50 amp pedestal.
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Old 07-03-2015, 12:14 PM   #6
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I have seen this.

Suggestion: Carry a 30-50 adaptrer (or 2) for this kind of park

Theory: There are a few devices in your Rig that are suspect
1:Converter.. Some of them will show up as a ground fault when they are in BULK mode..others inFloat mode and well designed ones will not do that

WaterHeater The heat element is contained in a water tight container and insulated (electrically) from it.. However what if it is NOT water tight?

Fridge: See water heater

Outside outlet.. Sometimes fills with rain water causing a ground fault.

Junction boxes (Two per slide) under the coach.
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Old 07-03-2015, 12:19 PM   #7
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I have this issue with my 50a connection at home. It is a 50a GFCI and it will trip when I first plug in. If I use the 30a connection (yes, I have both, previous MH was 30a), after the batteries get charged above bulk mode, then I can switch to the 50a and it works fine. I plan on changing the 50a GFCI to a normal 50a breaker.
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Old 07-04-2015, 06:55 AM   #8
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Originally Posted by ShapeShifter View Post
I agree with mel on this one: there is likely a ground fault on the coach: disconnect everything, and make connections one at a time until you find out where it is.



Actually, I would think that tying the neutral to the ground at the adapter would cause more problems and would make the GFCI trip more often. Adding that connection would create a loop where some of the neutral current from the rig could cross over to the ground, bypass the GFCI, and connect back up with the neutral connection back at the main service entrance breaker panel. With some of the neutral current flowing through the grounding conductor, the GFCI will see an imbalance in the hot and neutral currents, and that will cause it to trip. By connecting neutral and ground at the coach, you would be creating an actual ground fault, the very thing that the GFCI is trying to detect and prevent.

There should be only one connection between the neutral and ground conductors, and that should be at the main service entrance panel and not in the motorhome. That main service entrance panel is back at the campground (or home) where the utility service first enters the property.



I'm not sure how you come to this conclusion. Most (all?) 50 amp pedestals do not have GFCI protection on the 50 amp outlet. Without a GFCI tripping, (or using specialized test instruments to measure a current imbalance in the hot and neutral) how would you know if you have a ground fault problem? It's quite possible that there could be a ground fault in the coach, and you'd never know it using a 50 amp pedestal.

It's very simple. If somebody keeps tripping the 30 Amp GFI it is because of loop currents between the legs. If the neutral and safety ground are connected in the adapter there is no loop current going through the GFI in the Pedestal. The problem is that a 50 Amp Pedestal makes the connection in the Pedestal. Moving it to a 30 Amp adapter keeps it out of the 30 Amp GFI. The only place neutral and ground are connected in the MH are on the generator side of the transfer switch because there is no other ground.
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Old 07-04-2015, 08:17 AM   #9
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Quote:
Originally Posted by nothermark View Post
It's very simple. If somebody keeps tripping the 30 Amp GFI it is because of loop currents between the legs. If the neutral and safety ground are connected in the adapter there is no loop current going through the GFI in the Pedestal. The problem is that a 50 Amp Pedestal makes the connection in the Pedestal. Moving it to a 30 Amp adapter keeps it out of the 30 Amp GFI. The only place neutral and ground are connected in the MH are on the generator side of the transfer switch because there is no other ground.
I guess I'm just not understanding your terminology.

You mention the GFCI tripping because of a "loop current between the legs" but a current loop between hot and neutral sounds like a normal circuit to me, that's the way it's supposed to work.

A GFCI trips when the current in the hot leg does not match the current in the neutral leg withing a small number of milliamps. Those two currents should be balanced. If they are not, that means that besides the hot and neutral, there is current flowing somewhere else, probably through the user to ground. That is a ground fault, and that is what will trip the GFCI.

Consider the "normal" connections:


The arrows in the diagram are sized proportionally to the current in the wire. When everything is working properly, the current in the hot and neutral lines are the same, the GFCI monitoring those lines sees that they are the same, and it is happy. There is no current flowing through the grounding conductor, as it should be.

If you tie the ground and neutral together in the adapter before the GFCI, it seems to me it would increase the chances of tripping the GFCI. Current is flowing through the hot line, and the GFCI is watching for the same amount of current to be flowing in the neutral line. If there is a connection from neutral to ground on the load side of the GFCI, then some of that current can flow through the grounding conductor rather than the neutral conductor. That is causing what I would call a ground loop, and that will trip the GFCI since the current in the neutral does not equal the current in the hot.

This shows that situation:


This is the same drawing, with the addition of the jumper you are proposing between the neutral and ground wires. Now, the same current is flowing through the hot lead, but on the return path some of that current can flow through the neutral wire, and some can flow through the ground wire. This current in the ground wire is not seen by the GFCI, it only sees that the neutral current does not match the hot current -- this is a ground fault, and that will trip the GFCI.

So, I'm confused not only by your terminology, but how such a connection could possibly improve the situation? By adding the jumper, you are not removing a loop current, you are adding a ground loop current. What am I missing in your theory, it doesn't seem to make sense to me?
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Old 07-04-2015, 08:26 AM   #10
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OP. My intention was to help others that may have had this problem.
There's no problem when there's no post GFCI. My new coach has some sophisticed electronics protecting my electrical system(s). That park electrician said THEY had the problem with their GFCI's and newer coaches. Moved to 50A site with no GFCI, and no problem. They have a outdated electrical code.
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Old 07-04-2015, 10:09 AM   #11
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Regardless of whether anybody here thinks the park should have GFCI or not, they do have it and it is not a code violation. In fact, GFCI (and AFCI too) are becoming more prevalent all the time as the newer code editions have generally expanded the requirement for them. And the fact is, this coach does have a ground fault somewhere and that needs to be fixed. Ground faults represent potentially dangerous situations. Yeah it's a pain to find out you have a power system problem, but shooting the messenger isn't a productive response.

The most common sources of RV ground faults are the fridge and water heater electric heater elements and the converter/inverter/charger. Usually these aren't really dangerous, but it's impossible to be sure without isolating the cause. Other good possibilities are frayed wires in the shore power cord, improperly wired 120v outlets (ground and neutral reversed), or neutral & ground bonded in the coach load center (breaker box).
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Old 07-04-2015, 10:22 AM   #12
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Quote:
Originally Posted by Fiesta48 View Post
Have you had this problem?
Just left a park where the 30 Amp service was Ground Fault Circuit Breaker protected. Every time I turned ON the post breaker it tripped a breaker on the RV, causing the post breaker to trip back OFF too. Even a qualified electrician could not get us power.
I tried using a GCFI circuit at my son's house and it trips both OFF too.
Moral: Can't use House or Post GFCI's

Asked why the park had GFCI's on 30A but not on 50A service, Answer, that was code. Park was behind a dam. Only place I ever saw this.
Thinking that the tripping RV breaker circuit has the hot and neutral switched down range somewhere or it just has a ground fault. I had a slight leak to ground with an overhead ac once and never did find it. Just couldn't run it on a gfi, was all and there was no shock to it's touch.
Then again, not sure if you're talking about a branch circuit or the RV main.
I've never seen a 30amp GFI in a campground, either.
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Old 07-04-2015, 10:30 AM   #13
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Others posted obvious choices so no repeat.

Consider your mh a very large "toaster".

It is nothing more than that to the outlet you are connecting to.

If there is any leakage current then the gfi does its job and performs a disconnect.

Next most mh have some sort of distribution point such as an actor load center or breaker panel.

These should be configured as SUP-PANEL meaning safety ground and neutral must be isolated.

They make gfi cords or you can make one to use to test your unit in your driveway to verify it is good.

Switch mode power units often have high leakage current so they can introduce currents on the safety ground but those currents should not cause gfi to trip but they can create a hot chassis if safety ground is bad.

They also can drive the gfi nuts if safety ground is connected to neutral in the wrong place like a borrowed ground.

Follow provided advise to isolate the cause and get it fixed.

While working verify everything is installed correctly and tight.
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