Electrical Problem needs a solution-Help!!!

[Waliczek]

I finished my teardrop trailer about 3 weeks ago, and I came across a trailer I could not pass up. It was free. A 1955 12ft Boles Aero. All Aluminum, skin and studs. I stripped it all out, and the 115 VAC wiring was garbage. I pulled it out and re-wired. Well, I wired the trailer for 120VAC, but I think I have a problem.

1. I installed a new entrance recepticle.
2. I ran this service line to a three circut main box. Using the standard method.
a. Black wire to the Positive buss
b. White wire to the negative buss
c. Bare wire was conected to the negative buss also.
3. All recepticle boxes are plastic, all plugs and switches are wired standard, and no wire tounching the metal skin, or the metal studs. (Boles Areo) All Aluminum.
4. GFI in kitchen area shows the ready light, indicating that all is wired correctly.

Problem: Volt meter shows 120 VDC when positive probe and negative probe touch the entrance recpticle. Also show 120 VAC when neg. probe touches the bare wire.
Howerever, when the positive probe is on the black wire, and I touch the metal skin, or stud with the neg. probe, I get a reading of about 25V. HOW Come???, and what to do. I don"t want to close up the walls before this problem is resolved. Can anyone help?
Tom

[jgalt]

I would say this is pretty normal. You said that the chassis and skin are isolated from the AC Neutral (White) and Ground? If this is the case, then you are just getting a 'poor' ground connection to real earth ground.

If you did the same test measuring between AC Hot (Black) and a metal rod driven into the earth, you'ld get a higher reading - maybe 60-80V I'm guessing.

One last item, Shouldn't the ground wire be connected to the frame? If this is done, any short of the AC Hot wire to the skin would blow the fuse. Otherwise, the hot wire could short, not blow the fuse - and you'l have a 'hot' camper! Any electricians out there please double-check this for me!

[Waliczek]

Hello,
I did not ground anything to the shin or chaisis. I was going to connect
my ground from the battery to to the skin and frame for the 12 V systemn,
and I did not think I should have both systems on the same ground. Maybe I am wrong, and it makes no difference. But if for some reason, the
trailer goes hot from a short, then the 12V appliances cold be ruined. Maybe I worry too much I am going to connect the ground from the box to ground, and see if that makes a difference.
Thanks for your thoughts. If any other ideas come to mind, please forward them on.
Tom

[David Alston]

I am not sure if this is the source of your problem, or if I have read your message correctly, but in a three wire AC system you have a hot wire, a neutral wire and a safety wire. The safety or ground wire is the bare one. You don't connect the bare wire to what you have termed the "negative". There is no true negative in an AC system. You should remove the safety wire from the netural terminal and connect it to a chassis ground so that it will function properly.

David.

[Waliczek]

Jgalt & Dave, Thank you, your adivse is correct and sound. As luck would have it, a long time licensed electrician came to the job site this morning, and he confirmed. I need to get the bare wire to the frame and chaisis, to complete the safety ground. Now when I touch the positive and the skin, I read 120V. That way if something shorts out, it trips the fuse.
Thanks again. I feel better about this whle thing.
Tom