Open Neutral?

[prndl]

My 2955RL is parked alongside my garage and is being powered by a 120 V 15A extension cord. Keeps the batteries charged.

I was cleaning the storage area and using my shop vac plugged in at the trailer side outlet. I also vacuumed out the dust and dirt in the outside compartment for the refer. I happened to touch the metal surround for the refrigerator outside compartment and got a shock. This was while the vacuum was running. I turned the vac off and I did not get a shock from the surround. The shop vac does not have a separate ground (three prong plug). I tried other devices plugged into the same outlet on the trailer and there was no shock. All were grounded plugs though.

Is there a open neutral on the trailer wiring? If so, how do I find it?

[rohrmann]

If you do not get shocked at any other time than when operating the shop vac, I would suspect there is a problem with the shop vac. Since you were not getting shocked with anything else plugged into the same outlet, I would get rid of that vacuum before you get a worse shock and not be able to tell about it.

[Ahdmeyer]

could it be possibly static electric from the vacuum?

[dhuhn]

You could get an outlet tester to find out if its wired right . Here is one on amazon
https://www.amazon.com/Receptacle-Te...%2C257&sr=8-10

[prndl]

OK. I have several of those testers and when I plug them in they all say "Correct"

This is very interesting....
I put my VOM on the outlet in the kitchen, the one with the GFI in it.
I get 24 volts across the ground and neutral.

I started to eliminate individual circuits by turning off the breakers one by one.
Each time I turned one off the Ground neutral voltage dropped by 2 volts and when I had turned them all off except the the kitchen I was down to 14 volts neutral to ground.

With the final circuit breaker off I tested for continuity across the neutral ground and there is none. This might be due to the GFI plug.

I sure don't want to pull out the power station but there is no other choice.

[rohrmann]

If you do not get continuity between the ground and the neutral, I would start checking the outlet the rig is plugged into, and if that is good, the next point would be the rig end of the shore cord or whatever type of cord you are using. You might also check all the connections in the rig's main panel, as loose connections, both 120 volt and 12 volt are quite common. The ground and neutral will have a common connection at the meter/main panel and then are separate from that point, but still should be the same potential. You should get no voltage reading across a neutral to ground.

[BB_TX]

Originally Posted by rohrmann

If you do not get continuity between the ground and the neutral, I would start checking the outlet the rig is plugged into, and if that is good, the next point would be the rig end of the shore cord or whatever type of cord you are using. You might also check all the connections in the rig's main panel, as loose connections, both 120 volt and 12 volt are quite common. The ground and neutral will have a common connection at the meter/main panel and then are separate from that point, but still should be the same potential. You should get no voltage reading across a neutral to ground.

I agree with all of Bob’s comments.

My thought is that there is a weak connection in your grounding circuits and/or neutral circuits somewhere. I checked all my wire connections in the power panel (hot, neutral, ground, 12 volts) when my trailer was about a year old and found a number of wire terminal screws not properly tightened. Some people have even had wires and/or terminals there damaged due to overheating of bad connections.

I would check the wire connections in the shore power outlet. It is also possible the wire connections in the connector on the back of the trailer you plug your power cord are not good. There have been a number of cases of burned connectors there due to bad wiring. And lastly, but probably least likely, would be wire connections in your power cord.

A newer two prong electrical appliance is supposed to be inherently shock proof. Can’t think of a way a two prong device could cause a voltage on a frame that is supposed to be grounded unless that frame is not properly grounded.

[prndl]

After pulling out the converter/power station and also my transfer switch and all the accompanying wiring out of the compartment, I started testing backwards. I found that the wall plug at my house I was using for my 120V source, one outlet was showing "open Ground".

Now why this did not show up using the tester inside the rig but only at the plug itself I don't know.

I replaced the duplex plug and all is good now. I just have to put all the switches and wiring back and all is well.

Another day of RV mysteries discovered and solved.

[BB_TX]

Originally Posted by prndl

............
I found that the wall plug at my house I was using for my 120V source, one outlet was showing "open Ground".

Now why this did not show up using the tester inside the rig but only at the plug itself I don't know.
...........

The only thing I can think of that caused that is that the frame of the trailer is grounded making it electrically common to all other grounds including the main ground wire back to your power source. Since the source ground was open, it is possible that the trailer frame had a weak earth ground thru the jacks, just enough to allow the testers to show good ground, but not good enough to actually provide a good safety ground to drain off that frame voltage.

On the positive side, you now have an intimate knowledge of your entire power distribution system.

[prndl]

From what I have discovered the neutral and ground buss bars in the trailer power center are not bonded to the case. That is, there is no continuity between them.

Since there is no actual ground to earth on the trailer the power circuit is treated like a sub panel. The ground used is the ground wire in the power cable back to the source.

Think of it like an electrical accessory. When you plug in an electrical device like a table lamp or toaster &tc, you don't run a ground to earth from the device when using it. The ground is in the power cord.

The trailer is an accessory plugged in to the pedestal.

edit: I should have read this first. The answer is in the article. https://www.rvtravel.com/hot-skin-vo...oubleshooting/


This is also why when I use my generator for power I use a bonded plug.
(Unless you are going to run an earth ground to the ground connection on the generator, which nobody ever does)

[BB_TX]

You are correct. By code the neutral and ground are only connected at a single point at the power source. Multiple connections create what is called a ground loop that allows current to flow thru the ground wire that should only flowing thru the neutral wire.

The main ground wire should be connected to trailer frame somewhere. If you were to meter the ground buss bar in your load center to trailer frame you should find zero ohms between the two. That does several things. It drains off any stray or induced voltage on the frame to eliminate “hot skin”. It also provides a path for a neutral/ground fault to trip your GFCI circuits. And it creates a ground path to trip a circuit breaker in the case of a short between a hot wire and frame.