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-   -   "Open Ground" (https://www.airforums.com/forums/f37/open-ground-155772.html)

Tao 08-23-2016 06:46 PM

"Open Ground"
 
I searched - did not find answer that seemed to fit.

Given:
2013 Airstream Intl. 19. As new condition just purchased.

I upgraded the two Interstates to AGM's and upgraded the charger/converter.

Now, today was the first time I decided to check the outlets inside the trailer with my little yellow, 3 diode tester (red, yellow, yellow lights).

Have 4 outlets in the trailer. ALL 4 test as Open Ground!! (center yellow light glows).

The power pole which is only 110 15 amp at U-Haul storage checks perfect. So power coming in is OK. But all of the interior outlets are showing Open Ground.

Everything seems to work and GFI does not trip and cut the power.

Question:
What in the world is going on?

Is this normal for a GFI circuit in an RV?

If not, how to resolve without spending a fortune at the dealership?

Thanks.

TG Twinkie 08-23-2016 07:03 PM

You could have a bad shore power cable adaptor. Since you are plugged into a 15 amp outlet you must be using an adaptor of some sort.
If you know how to use a multimeter. You can check for continuity in the adaptor as well as the shore power cable to the panel inside the coach.

HiJoeSilver 08-23-2016 07:18 PM

I hope it's only showing open ground!!!

If it's showing open neutral disconnect power you've got a serious problem.

The open ground is normal in an RV. The tester is designed for home circuits where the neutral and ground are connected in the breaker panel. In an RV the neutral and ground are NOT connected in the breaker panel, so the tester is trying to read a ground connection between neutral and ground but it's not there and thinks there is a problem.
You can check your voltages and resistances between outlet plugs. Hot to neutral, and hot to ground should show 120v, OL resistance. Neutral to ground should show 0 volts, OL resistance.
Ground to metal shell should be 0 volts and 0 resistance.

If the shore power outlet showed open ground then there would be a problem. On that end.

Al and Missy 08-23-2016 07:44 PM

Quote:

Originally Posted by HiJoeSilver (Post 1840129)
I hope it's only showing open ground!!!

If it's showing open neutral disconnect power you've got a serious problem.

The open ground is normal in an RV. The tester is designed for home circuits where the neutral and ground are connected in the breaker panel. In an RV the neutral and ground are NOT connected in the breaker panel, so the tester is trying to read a ground connection between neutral and ground but it's not there and thinks there is a problem.
You can check your voltages and resistances between outlet plugs. Hot to neutral, and hot to ground should show 120v, OL resistance. Neutral to ground should show 0 volts, OL resistance.
Ground to metal shell should be 0 volts and 0 resistance.

If the shore power outlet showed open ground then there would be a problem. On that end.

If he is plugged into a service which checks OK, the tester should be able to see back to the bond at the power panel at U-haul.

Ground is probably open in the trailer.

Al

Tao 08-23-2016 07:51 PM

I'll see if I can find a 30 amp outlet locally to plug into. IF that clears the Open Ground (it is just the ground that is open, not the neutral), then I know the adapter cable or the extension cord is screwed up.

Make sense?

TG Twinkie 08-23-2016 07:52 PM

An open ground is NOT normal in an RV. The panel in the coach is considered a sub panel where the neutral and ground are NOT bonded (connected together). This sub panel is connected to a main panel in which the neutral and ground are bonded.
Therefor if all is wired correctly your tester should not indicate an open ground.
You need to locate the problem and have it corrected.

Tao 08-23-2016 07:53 PM

Quote:

Originally Posted by HiJoeSilver (Post 1840129)
I hope it's only showing open ground!!!

If it's showing open neutral disconnect power you've got a serious problem.

The open ground is normal in an RV. The tester is designed for home circuits where the neutral and ground are connected in the breaker panel. In an RV the neutral and ground are NOT connected in the breaker panel, so the tester is trying to read a ground connection between neutral and ground but it's not there and thinks there is a problem.
You can check your voltages and resistances between outlet plugs. Hot to neutral, and hot to ground should show 120v, OL resistance. Neutral to ground should show 0 volts, OL resistance.
Ground to metal shell should be 0 volts and 0 resistance.

If the shore power outlet showed open ground then there would be a problem. On that end.

I wondered if it was normal. Makes sense when you explain it.
Guess the true test will be if plugged into a 35 amp outlet with no adapter do I have the same open ground result on the little tester.

Jack

Tao 08-23-2016 07:56 PM

Quote:

Originally Posted by TG Twinkie (Post 1840142)
An open ground is NOT normal in an RV. The panel in the coach is considered a sub panel where the neutral and ground are NOT bonded (connected together). This sub panel is connected to a main panel in which the neutral and ground are bonded.
Therefor if all is wired correctly your tester should not indicate an open ground.
You need to locate the problem and have it corrected.

Oh, OK, that is 180 degrees different.

I'm thinking it's the adapter as I tightened all of the connections at the AC side the breaker box.

Gotta find a 35 amp electrical outlet. We have a few parks here in the area at Jordan Lake I can try.

HiJoeSilver 08-23-2016 08:03 PM

Sorry misread the symptoms. Plugged in to shore power you should show a good ground.

Tao 08-23-2016 08:07 PM

Quote:

Originally Posted by HiJoeSilver (Post 1840150)
Sorry misread the symptoms. Plugged in to shore power you should show a good ground.

No problem, appreciate the good intention.

Jack

A W Warn 08-23-2016 08:08 PM

I suggest you should use a multi-meter to test continuity of the ground wire in your adapter (to eliminate that as an issue)

If the adapter is not the issue and if you used an extension cord: check continuity of the ground wire within the extension cord.

If the extension cord is not the problem and if there has been a recent upgrade/change to your 120v system: remove the breaker box cover (disconnect 120v first) and look at the ground bar where all of the bare copper wires are connected to see if one bare copper wire has been left loose.

If no wire has been left loose at the ground bar inside the breaker box: remove the individual receptacles that show the open ground (disconnect 120v first), starting at the receptacle closest to the breaker box, to see if the ground wire is loose.

HiJoeSilver 08-23-2016 08:17 PM

Quote:

Originally Posted by Tao (Post 1840151)
No problem, appreciate the good intention.

Jack

Nope I need to be more careful, pay more attention to what I'm typing, especially when helping diagnose electrical issues.
Don't need others to hop on yes you should, I feel bad as it is.

HiJoeSilver 08-23-2016 09:19 PM

Quote:

Originally Posted by A W Warn (Post 1840152)
I suggest you should use a multi-meter to test continuity of the ground wire in your adapter (to eliminate that as an issue)

If the adapter is not the issue and if you used an extension cord: check continuity of the ground wire within the extension cord.

If the extension cord is not the problem and if there has been a recent upgrade/change to your 120v system: remove the breaker box cover (disconnect 120v first) and look at the ground bar where all of the bare copper wires are connected to see if one bare copper wire has been left loose.

If no wire has been left loose at the ground bar inside the breaker box: remove the individual receptacles that show the open ground (disconnect 120v first), starting at the receptacle closest to the breaker box, to see if the ground wire is loose.

Spot on.
There are lots of potential problem points. Chasing electrical gremlins is a pain. Bad connection on ground from post to adapter to 30 amp plug, to 30 amp receptacle on side of trailer to the back side of that same receptacle to the ground bar in the breaker panel.



Before checking other things check the ground continuity in the adapter with a multi meter. Plug one multimeter prong into ground inlet and other to ground prong it should read zero resistance. If your multi meter probes only have tiny metal tips showing pull the rubber around them there are probably rubber boots that come off to expose longer probes.

Next I would take a quick look at the breaker panel. Check all the ground wires are connected and tight.

If that looks good I would state some progressive troubleshooting from source to ground bar in breaker panel.

Connecting the adapter to your power cord then check continuity from the adapter ground prong to the ground prong on the 30a connector, the ground is the one with the little ear. This will test the connection between the adapter through the power cord. You may not be getting a good connection there.

If that connection tests good then next step. Connect the power cord to the trailer inlet.
In a 19' trailer you will probably be able to pull the power cord end all the way into your trailer getting the end you normally plug into shore power close to the breaker panel. With the power cord connected to your trailer inlet. Check the resistance from the ground prong on the adapter to the ground bar in the breaker panel. Should be zero.

If all previous tests were good and this is not good then the connection on the back of the power inlet to the trailer is probably bad. I know AS had an issue a few years ago with those connections not being tight. You'll have to unscrew the trailer power inlet from the trailer side pull it out gently and check continuity and connections from exterior and interior side of the power inlet.
If you follow the progression you're trying to find the broken link in the chain. Good trouble shooting usually checks the ends Then starts at one and continues down the line.

Of note, the receptacles are different than house receptacles. When you remove them you'll have to remove the back of it, normally a tab on each side to pop it off. The wires are pushed down into slots in the back of them pinching them between copper prongs. Normally the wire is continuous from beginning to end. Meaning as it goes through outlet to outlet, the wire is never really cut. So even if the ground was loose in one it should be a continuous run to the next.

Long and verbose but hope it helps.

HiJoeSilver 08-23-2016 10:06 PM

Ok on second thought, check the wires on the back of the gfci first. Chances are that is the one spot AS uses a normal house type outlet fixture. A loose connection there will affect the other 3 downstream outlets.
Do you have outlets that aren't on that gfci circuit, probably not in a 19' trailer. But if you do check those with circuit tester.

Electrical has to many darn possibilities.

cwf 08-23-2016 10:22 PM

Make SURE you remove ALL AC power before tinkering with your wires.. Just sayin'

xrvr 08-24-2016 06:21 AM

Try a different adapter.

Tao 08-24-2016 01:40 PM

Wow, so simple yet the path to the solution took a long time.

Just got back from the trailer. Bought a new 50' extension cord and adapter at Walmart on the way.

Plugged in the new extension cord, problem completely gone. Inspected the old one and must have driven over it because I found a cut in the cord that must have shorted out the ground wire.

So simple!
Thanks for the help folks, I appreciate it!

Jack


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