electrical grounding concern - Page 2 - Montana Owners Club

Biggjb · 04-30-2015, 04:29 AM

Quote:

quote:Originally posted by DonPd

I made a 50 amp tester and use it before plugging in my power.

Site for the 50 amp tester;
http://www.myrv.us/electric/Pg/tester_50amp.htm

Site for 30 amp tester;
http://www.myrv.us/electric/pg/tester_30amp.htm

Here is some information that might save your life.
http://www.noshockzone.org/are-little-shocks-ok/

http://www.noshockzone.org/

Ok this is were I need an electician who knows how a 5th wheel is wired. The technician spent 2 days with my 5er. I bought a 30 amp shore cord and used it. The grounding problem was still still, we took apart the twist lock plus at the trailer and replaced it...stilldid not resolve the problem. With the power on, he tested one leg of the 50 amp breaker, measure from ground to one leg and it read 247V and the other leg read 0V. He the measured again but this time he measured from neutral and both legs measured 120V. He thinks some where in the 5er a neutral has bonded to ground. What is also funny is when he turne off all breakers in the trailer, he still read 47V across the water heater and the second AC unit, but I am only wired for a second AC unit. I checked the seconded AC unit wires and they are all seperated. Any further suggestions would be greatly appreciated. We bought it at camping world in Syracuse and we are considering taking it to them for repair.

rohrmann · 04-30-2015, 09:13 AM

The only way you are reading 247V to ground on one leg and 0 volts to ground on the other leg is the one leg you are reading 0 volts to ground is directly shorted to that ground. That is also why, from that ground connection to the other leg you are reading 247 volts. If you haven't already checked, as was suggested, using another power cable that works on other rigs, that should be done. If that still gives you the same condition, then somewhere in your rig, you have a ground cable and one of the hot leg cables burnt together, and that is also why you are getting shocked when touching metal on your rig when you are standing on the ground. This needs to be repaired before you burn up everything in your trailer, which may have already happened.

Biggjb · 04-30-2015, 06:44 PM

Quote:

quote:Originally posted by rohrmann

The only way you are reading 247V to ground on one leg and 0 volts to ground on the other leg is the one leg you are reading 0 volts to ground is directly shorted to that ground. That is also why, from that ground connection to the other leg you are reading 247 volts. If you haven't already checked, as was suggested, using another power cable that works on other rigs, that should be done. If that still gives you the same condition, then somewhere in your rig, you have a ground cable and one of the hot leg cables burnt together, and that is also why you are getting shocked when touching metal on your rig when you are standing on the ground. This needs to be repaired before you burn up everything in your trailer, which may have already happened.

The power cord has been ruled out. The twist lock at the trailer has been ruled out. He was then going to rewire from the twist lock to the distribution panel but he said that would cost a fortune and he could not guarente it would work. I am not sure how to start looking for the faulty circuit. Would measuring across the neutral and ground of each circuit in the distribution panel work?

rohrmann · 04-30-2015, 07:22 PM

I would first, if you have not already done this, make sure the 50 amp main breaker in the trailer's distribution panel is off. Then, you will have to remove the cover to access the terminals of the breakers. Inside the panel, you will also see, what should be a white wire, the neutral, and also a green wire, which is the ground. If everything was normal, using a voltmeter, from either the ground or the neutral to either of the hot legs that attach to the 50 amp breaker, you should be able to read about 120 volts. What you were saying previously, is you were reading 120 volts to each hot leg from the neutral, but 247 volts from the ground to one of the hot legs and 0 volts from the other hot leg to the ground. What that is telling me, if you are still reading these voltages at the trailer panel, is the hot leg you are reading 0 volts to ground is shorted directly to the ground wire. If this is still the case, somewhere between the receptacle where your shore cable connects on the outside of the trailer to the panel where your trailer breakers are located, is where the two cables are electrically connected/shorted together. You will have to physically expose and inspect the entire run of cables between these two points to locate the place where these cables are shorted.

Biggjb · 05-02-2015, 03:37 AM

Quote:

quote:Originally posted by rohrmann

I would first, if you have not already done this, make sure the 50 amp main breaker in the trailer's distribution panel is off. Then, you will have to remove the cover to access the terminals of the breakers. Inside the panel, you will also see, what should be a white wire, the neutral, and also a green wire, which is the ground. If everything was normal, using a voltmeter, from either the ground or the neutral to either of the hot legs that attach to the 50 amp breaker, you should be able to read about 120 volts. What you were saying previously, is you were reading 120 volts to each hot leg from the neutral, but 247 volts from the ground to one of the hot legs and 0 volts from the other hot leg to the ground. What that is telling me, if you are still reading these voltages at the trailer panel, is the hot leg you are reading 0 volts to ground is shorted directly to the ground wire. If this is still the case, somewhere between the receptacle where your shore cable connects on the outside of the trailer to the panel where your trailer breakers are located, is where the two cables are electrically connected/shorted together. You will have to physically expose and inspect the entire run of cables between these two points to locate the place where these cables are shorted.

Rorhmann, if I understand you correctly, the problem could be with the main line between the twist lock and the distribution panel. If that is the I should be able to do a continuity check between either of the hot legs and ground. This I did not do. I hope this is the problem as I really am not looking forward to checking ever circuit in my 5er.

rohrmann · 05-02-2015, 05:10 AM

Good luck and be very careful doing all this. Just make sure you are fully disconnected from shore power before testing anything. I wish we were closer, could assist you. I'm just wondering what happened to cause this, maybe a critter got in and chewed on the wires or did you do any work on the rig recently? When you are testing, the hot leg that is reading 0 volts should have 0 or very little resistance to the ground, where the other hot leg should have infinite resistance to the same ground, or close to infinite. The neutral should also show infinite to both hot legs, and the hot legs should also show infinite to each other. If all these tests show what I have described, then you definitely have a problem in that main run of cables to the panel.

Biggjb · 05-02-2015, 09:28 AM

Quote:

quote:Originally posted by rohrmann

Good luck and be very careful doing all this. Just make sure you are fully disconnected from shore power before testing anything. I wish we were closer, could assist you. I'm just wondering what happened to cause this, maybe a critter got in and chewed on the wires or did you do any work on the rig recently? When you are testing, the hot leg that is reading 0 volts should have 0 or very little resistance to the ground, where the other hot leg should have infinite resistance to the same ground, or close to infinite. The neutral should also show infinite to both hot legs, and the hot legs should also show infinite to each other. If all these tests show what I have described, then you definitely have a problem in that main run of cables to the panel.

Bob, I isolated the main wires coming into the distribution panel from the shore power. The resistance from ground to both hot legs was infinite. Also, the resistance from neutral to both hot legs was also infinite, and the resistance between both hot legs was
also infinite. To me this means the main wiring to the distribution panel is goo. I wonder if I should check each circuit the same way

Phil P · 05-02-2015, 12:50 PM

Hi

I have been watching you progress.

I think you have a problem with the distribution panel itself.

I would disconnect the power and remove the main breaker, shut off all the rest of the breakers and check the L1 and L2 to ground / natural and see what you get.

One question is you unit generator ready?

Phil P

Biggjb · 05-02-2015, 03:36 PM

Quote:

quote:Originally posted by Phil P

Hi

I have been watching you progress.

I think you have a problem with the distribution panel itself.

I would disconnect the power and remove the main breaker, shut off all the rest of the breakers and check the L1 and L2 to ground / natural and see what you get.

One question is you unit generator ready?

Phil P

Phil, I had some very interesting test results today. With the main wires totally removed from the distribution panel the resistance from all 4 legs to each other was infinite. Which to me meant the main wiring was good. However, with no power going to the 5er and ALL breakers turned off, I measure the resistance from the ground bar to all the beakers and they all were infinity...but when I measured from the hot leg which originally measured 0V when the power was turned on, it read 0. To me this means there is a ground from one of the trailers circuit which is now touching the hot leg.

What I think I should do next is check each circuit the same way by taking each neutral, ground and hot lead for each circuit to see if they are grounded to each other. This way I hope I can determine which circuit I will need to rewire.

Greg

rohrmann · 05-02-2015, 04:51 PM

You should be able to check each breaker terminal, with the breakers open, and verify a grounded hot leg condition just by checking the common ground in the panel to each breaker.

Phil P · 05-03-2015, 11:09 AM

Hi

The reason I would remove the main breaker is to eliminate it as the problem. The main breaker is the only one that has L1 and L2 in it. The rest of the breakers are on only one L1 or L2. If you had the main breaker removed and showed closed circuit from one L to Ground and all breakers off then you have a problem right there in the power center.

Phil P

Biggjb · 05-10-2015, 03:08 PM

Quote:

quote:Originally posted by Phil P

Hi

The reason I would remove the main breaker is to eliminate it as the problem. The main breaker is the only one that has L1 and L2 in it. The rest of the breakers are on only one L1 or L2. If you had the main breaker removed and showed closed circuit from one L to Ground and all breakers off then you have a problem right there in the power center.

Phil P
Hi Phil,

Just returned from Camping World in Syracuse and they stated that there was a ground from one L2 direct to the converter. They rewired from where the shore power enters the 5er right up to the distribution panel and to the converter. The problem has been solved. As it took 2 days to complete the repairs, I took the time to buy a surge protector and will never leave home with it. I would like to thank all who guided me through this mishap.

rohrmann · 05-10-2015, 06:18 PM

So, one of the hot leg cables was grounded between the panel and the outside connector? Did they say just where it failed?

paulinbaja · 05-12-2015, 05:20 AM

It is not clear to me, did the issue stop after the electrician worked on the pedestal? Check with your neighbors if they have the same problem the park could have a serious problem with a transformer or High Voltage wiring underground.

Disconnect!

Phil P · 05-12-2015, 02:54 PM

Hi

Your problem should have gone away when you switched the inverter circuit breaker off!!!

Phil P

Biggjb · 05-12-2015, 03:12 PM

Quote:

quote:Originally posted by paulinbaja

It is not clear to me, did the issue stop after the electrician worked on the pedestal? Check with your neighbors if they have the same problem the park could have a serious problem with a transformer or High Voltage wiring underground.

Disconnect!

The issue did not stop. The electrician corrected a situation he said was normal practice many years ago... The neutral was grounded to ground at the pedestal. This may have corrected the issue at the pedestal, however, the damage was already done to me 5er. We checked with our neighbors and they did not have any issues. The owner has requested the electrician to investigate the grid in question. Unfortunately I left before knowing any result of the investigation.

Biggjb · 05-12-2015, 03:14 PM

Quote:

quote:Originally posted by rohrmann

So, one of the hot leg cables was grounded between the panel and the outside connector? Did they say just where it failed?

They did not state where the failure occurred only that they needed to run new wires to the convertor.

Biggjb · 05-12-2015, 03:17 PM

Quote:

quote:Originally posted by Phil P

Hi

Your problem should have gone away when you switched the inverter circuit breaker off!!!

Phil P

Phil, you may be correct, however, I will never know as issue appears to be solved.

rohrmann · 05-12-2015, 05:03 PM

Having a ground and neutral tied together will not cause the problem experienced by Biggjb. The ground and neutral are always tied together at the main/meter panel, that is where the ground to the customer side of the panel originates, so having it connected together somewhere else in the system will not cause arcing and fire. The utility provides the hot legs and a neutral. The problem that happened was solely inside his rig, but unless the rig was taken apart, he may never know what happened. It may have been a critter that chewed on the wires, which caused them to short together.

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