Community Forums

hawk232 · 12-10-2012, 06:10 PM

just bought a 2006 puma 25bh and brought it home saturday.

When I bought the camper the initial problem was that with any extension cord I was getting about 37V through the frame of the camper. Switching breakers off one at a time would slowly reduce the voltage until all of them were off. When all breakers were off, including the main, I still had about 6V running through the frame.
The next day I took two grounds off of the frame, sanded everything to bare metal, put di electric grease then re installed. After doing this, when using a grounded cord I only have 1.5V running through the frame. However, using a cord without a ground (ground broken off) I still have about 6V running through the frame. I know that a ground should always be used etc etc…. but there is never a guarantee that the ground will be functioning properly at campgrounds so I would like to get it down to below the 2V that I have heard is considered acceptable per code.
Next I pulled out the inverter and cleaned the ground wire there. Afterwards I am at roughly 4V. I get 4V going from the frame to the earth and I can duplicate that EXACT voltage by going from the ground buss bar in the inverter to the neutral buss bar. It seems that somehow 4-6V is being introduced into the neutral circuit. Any ideas?

For what it is worth I have a pop up that only has .9V with the same un grounded ext cord, so I know its possible and that something must be wrong with the travel trailer.

ruffian · 12-10-2012, 08:17 PM

Reversed Neutral. No Doubt.

The ground is not the problem. Voltage induced into the ground/chassis is because of a crossed Hot/Neutral at some point in the circuit. Remember that the breakers are on the "hot" wire so a bad neutral circuit probably won't be shut of with the on-board breakers.

Chances are good that if you measure voltage between your coach chassis and a good ground you will see more than 37 V.

Thehammer · 12-10-2012, 08:19 PM

First, I am not certain how you are measuring the voltage o the frame. What is your "ground" or reference that you are measuring this voltage to.

When connecting your TT to an electrical supply, you have a hot black wire (and a second hot red wire if connected to 50a 240 VAC), a neutral white wire and a ground wire that is either green or bare copper. That ground wire should be connected to the frame. That ground wire should also be connected to your electrical ground and to a ground pole inserted into the dirt in the physical ground. Note that at the primary electrical box the white neutral and ground wires are connected together.

If you are measuring the voltage to the frame to that electrical ground wire (green or bare copper) then either there is no connection between where the ground comes into your TT and the frame, or your electrical ground source is defective.

There are a couple of tests to try (note that the electrical plug must be disconnected from the TT. I also recommend removing the battery or at least remove the fuse from the battery):

1) Disconnect the electrical supply to your TT. Unplug it. Take a DVM (volt ohm meter) and set it to resistance on the lowest setting which should be x1 ohm. Touch the two leads together. It will read close to zero but may read a bit above zero. Ideally, you would like to get a value close to this in this test. Now connect one lead to your chassis. It is important that this be a good connection. Connect the other lead to another point on your chassis. You should read a value a little above what you got when you touched the two leads together. If not, one or both of your contacts to the chassis is not very good because of pant, rust, oil, etc. repeat this until you get a good chassis ground. Now insert the other lead into the ground(!) electrical feed to your trailer. The resistance should be almost as low as when you touched the two leads.

http://www.myrv.us/Imgs/PDF/30-amp%20Service.pdf

Note that the battery ground should also be connected to the chassis ground so you could use that as one of your chassis ground tests.

If you read a high resistance, then you have to trace where this wire comes in and should be connected to the chassis. I would start looking inside the circuit breaker box. Look for where that green wire (or bare copper) comes in and how it is connected to the chassis.

2) Are you certain that the ground in the electrical supply is good? The easiest way to test this is with one of those neon plug testers, but that is more difficult if you are hooked up to a 240 VAC 50 A supply. If you are hooked up to a 30 A, then get an adapter and a tester from a hardware store. The other way to test this is like the above with a voltmeter set to resistance, but I hesitate to recommend this because you will be dealing with a plug that has power to it. Inserting the DVM lead into the wrong part of the plug could get you killed or just blow out your DVM.

I hope others chime in and look at my suggestions to make certain I am correct, prior to doing this.

As always with electricity, it can get you killed. Do not do anything unless you are qualified to do so. While the TT has only 12 V when not connected to AC, there is a considerable amount of power in that battery and messing up can cause the battery to blow up.

Thehammer · 12-10-2012, 08:31 PM

I forgot to add that you should check to see that your extension cord that is connected to the TT could also have a break in the ground wire.

The comment about neutral / hot being switched is interesting. If you are running 30A, that is possible, but if your chassis is actually electrically grounded through the ground wire in your AC power, I do not understand how it could float and give you the voltage you are reading.

If you are running 50 A, which is 240 VAC, if one hot and the neutral are switched, you would have stuff blowing out in the TT because half the 120 VAC circuit in the TT would be 240 VAC. Boom to your TV or microwave!

I also forgot to suggest that you try that neon electrical tester in the electric plugs inside the TT. That should tell you if the ground circuit to the TT is good, but would not confirm if the chassis is connected to the ground wire.

Thehammer · 12-10-2012, 08:36 PM

It could also be that your ground and neutral are tied together inside your TT, which is an electrical hazard. The ground and neutral must be separate and not tied together except at the main circuit panel that supplies the AC. It must also be separate at any subpanels.

You could also check that by disconnecting the power and then use the DVM to check resistance between neutral and ground. It should be infinite. If not, it could be a wiring problem or an electrical problem in any connected appliance.

hawk232 · 12-10-2012, 09:04 PM

Quote:

Originally Posted by ruffian

Reversed Neutral. No Doubt.

The ground is not the problem. Voltage induced into the ground/chassis is because of a crossed Hot/Neutral at some point in the circuit. Remember that the breakers are on the "hot" wire so a bad neutral circuit probably won't be shut of with the on-board breakers.

Chances are good that if you measure voltage between your coach chassis and a good ground you will see more than 37 V.

good stuff, i will have to see if i can find anything obvious. maybe a previous owner replaced an outlet and swapped wires or something.

Quote:

Originally Posted by Thehammer

First, I am not certain how you are measuring the voltage o the frame. What is your "ground" or reference that you are measuring this voltage to.

When connecting your TT to an electrical supply, you have a hot black wire (and a second hot red wire if connected to 50a 240 VAC), a neutral white wire and a ground wire that is either green or bare copper. That ground wire should be connected to the frame. That ground wire should also be connected to your electrical ground and to a ground pole inserted into the dirt in the physical ground. Note that at the primary electrical box the white neutral and ground wires are connected together.

If you are measuring the voltage to the frame to that electrical ground wire (green or bare copper) then either there is no connection between where the ground comes into your TT and the frame, or your electrical ground source is defective.

There are a couple of tests to try (note that the electrical plug must be disconnected from the TT. I also recommend removing the battery or at least remove the fuse from the battery):

1) Disconnect the electrical supply to your TT. Unplug it. Take a DVM (volt ohm meter) and set it to resistance on the lowest setting which should be x1 ohm. Touch the two leads together. It will read close to zero but may read a bit above zero. Ideally, you would like to get a value close to this in this test. Now connect one lead to your chassis. It is important that this be a good connection. Connect the other lead to another point on your chassis. You should read a value a little above what you got when you touched the two leads together. If not, one or both of your contacts to the chassis is not very good because of pant, rust, oil, etc. repeat this until you get a good chassis ground. Now insert the other lead into the ground(!) electrical feed to your trailer. The resistance should be almost as low as when you touched the two leads.

http://www.myrv.us/Imgs/PDF/30-amp%20Service.pdf

Note that the battery ground should also be connected to the chassis ground so you could use that as one of your chassis ground tests.

If you read a high resistance, then you have to trace where this wire comes in and should be connected to the chassis. I would start looking inside the circuit breaker box. Look for where that green wire (or bare copper) comes in and how it is connected to the chassis.

2) Are you certain that the ground in the electrical supply is good? The easiest way to test this is with one of those neon plug testers, but that is more difficult if you are hooked up to a 240 VAC 50 A supply. If you are hooked up to a 30 A, then get an adapter and a tester from a hardware store. The other way to test this is like the above with a voltmeter set to resistance, but I hesitate to recommend this because you will be dealing with a plug that has power to it. Inserting the DVM lead into the wrong part of the plug could get you killed or just blow out your DVM.

I hope others chime in and look at my suggestions to make certain I am correct, prior to doing this.

As always with electricity, it can get you killed. Do not do anything unless you are qualified to do so. While the TT has only 12 V when not connected to AC, there is a considerable amount of power in that battery and messing up can cause the battery to blow up.

for ground i am using an actual earth ground (rod in the ground). i also suppose i could have stated its just 110 30A

everything on the house outlet is good, ground, polarity etc... also, like stated in my original post, when i use a cord with a proper ground i only have 1.5V. for testing purposed i am using a cord that the ground was broken off of to make sure if I end up at a campground with a screwed up ground, i wont get shocked!!

i will check the resistance of the ground to the frame but i feel pretty confident it is good as i sanded down to bare metal on the frame, cleaned terminals, and reassembled with di electric grease.

Quote:

Originally Posted by Thehammer

It could also be that your ground and neutral are tied together inside your TT, which is an electrical hazard. The ground and neutral must be separate and not tied together except at the main circuit panel that supplies the AC. It must also be separate at any subpanels.

You could also check that by disconnecting the power and then use the DVM to check resistance between neutral and ground. It should be infinite. If not, it could be a wiring problem or an electrical problem in any connected appliance.

more good info! i will check resistance between the two, they do not appear to be tied together, or if they are there is a voltage difference between the two. when checking between the neutral and ground buss bars i get a voltage the coincides with the voltage running through the chassis if that makes sense??

ruffian · 12-11-2012, 10:14 AM

Hire a Trained Electrician. While the Forum is a very helpful place, none of us will donate to buy the casket.

This is a complicated issue. Contrary to current belief, everything can't be learned on the Internet. Obviously being none of us agree on the answer, someone doesn't know what they are talking about.

Hire help.

hawk232 · 12-11-2012, 10:40 AM

not gunna happen. i have it down to only 6-9V now, which is no where close to lethal. also, it is only when i am using an un grounded cord therefore i KNOW when i am going to be charging it and the proper precautions can be taken.

i would imagine the reason for the different answers is that there are several things that can cause it. and you are correct, as with any form of diagnostic, people will be wrong, and someone will be right.

thanks for your advice though!

Thehammer · 12-11-2012, 03:43 PM

Quote:

Originally Posted by hawk232

for ground i am using an actual earth ground (rod in the ground). i also suppose i could have stated its just 110 30A

everything on the house outlet is good, ground, polarity etc... also, like stated in my original post, when i use a cord with a proper ground i only have 1.5V. for testing purposed i am using a cord that the ground was broken off of to make sure if I end up at a campground with a screwed up ground, i wont get shocked!!

OK, now I know a little more about what you are doing. I withdraw most of my previous comments - sorry I misunderstood. I did not realize that you are intentionally removing the ground from your electrical connection. In my humble opinion, you are checking for a situation that should never occur if you take a simple precaution: Buy a plug in circuit tester and a 30A to 15A adapter. Use that on the campground plug prior to connecting. That will tell you I'd the ground and neutral are good. It will also tell you if the neutral and ground are reversed. If the neutral is bad (floating) then you could get 240V AC to your TT. This test will allay your concern about not having a good ground.
Then, after you have made the connection to your TT, check an interior plug with the same tester to insure that you do not have a broken ground in your cord.

Many others in this site have recommended using a surge protector and voltage monitor. Personally, I think they are expensive. And I have had a surge protector fail in my house because even the very best surge protector can only handle so much power. However, that is just my opinion about surge protectors and I do not have the science to back it up.

With all due respect, your voltage test is misleading because you are reading voltage with (almost) no load on it. The voltage you are reading could have almost zero current and therefore almost no power. Voltage, by itself means very little.

For example, have you ever gotten a static charge shock by rubbing along a carpet? That is several thousand volts.
I used to demonstrate an electrical discharge of several inches through the air between two people and they could not feel hardly anything.

It is not voltage that kills, it is current.

http://www.physics.ohio-state.edu/~p...l_current.html

The voltage you are reading, even if it is ten's of volts can be quite harmless if there is no current. It is not uncommon for a metal roof to have 100 volts induced by overhead voltage lines, but not enough current for it to matter.

So my suggestion: relax, forget your quest and go out and purchase yourself that circuit tester and adapter for about $10.

Thehammer · 12-11-2012, 03:47 PM

I meant to say that the tester "will tell you if the neutral and hot are reversed". Sorry for my error.

hawk232 · 12-11-2012, 08:09 PM

hammer- thanks for the response. i must have been reading your mind because by lunch today i decided to drop the hypothetical testing and just accept that it will probably never matter. i already have a circuit tester, no contact tester and multi meter that are in the camper.

i was just having a stubborn mental issue that even with a bad ground I should have no voltage. because of this i got it down from 40V with no ground down to about 6, so i did do SOME good... not sure it offsets the mental stress though!! lol thanks again!