Getting Shocked...

[movinair]

I am in the process of gutting a 1957 Overlander (26ft). I plugged it into external power, and all the interior lights work. This is handy as I work inside, to see what I'm doing.
However when I went outside to try to unscrew the banana wrap*, and touched the metal screws, I got bitten by an electric shock. Does that mean I have a wire that is grounding out somewhere that shouldn't be? How can I find it?
*Not sure what that part is called - the aluminum curved bar that the floor tucks under and the underbelly pan connects to. It is very corroded, so I wondered if the electricity flowing through it accellerated the process, or if it's just because its from 1957.

any help greatly appreciated.
matthias

[Jammer]

Get somebody qualified to look at it.

Yes you probably have a wire grounding out somewhere. Possibly a previous owner did that deliberately out of ignorance.

The trailer shell should be grounded to the grounding pin of the shore power connection. I believe a 1957 may be old enough that this wasn't done in the stock wiring, and the quality of any later rework may have been variable.

[TG Twinkie]

It sounds like your power source is not wired correctly. It could also be a simple matter that the umbilical cord is the problem or that the neutral wire is grounded to the chassis of the trailer. Is this a 20 amp circuit? By that I mean. Do you use a regular extension cord to power the trailer? In any case the first thing you should do is get a tester for checking your power source. Most are available at places like Lowes or Home Depot for a nominal fee. This testing device will tell you if the neutral and hot leg are reversed. If they are reversed and the neutral is grounded in the trailer, the skin of the trailer will be hot when you are plugged in. If everything at the source checks out, then plug the tester into an outlet in the trailer. Here are a couple of websites with info. www.dasplace.net and www.myrv.us with info. If you have questions post them here.
If you don't feel qualified to do this checking yourself then get a qualified person to help you out. Even 120volts can kill you. I would highly recommend that you unplug the trailer until you get the problem resolved.

[vswingfield]

It is also possible that the outlet you have the trailer plugged into is wired backwards or the trailer umbilical is wired backwards. The outlets wired incorrectly is more common than you might think. It's not unusual for campgrounds to have an outlet wired incorrectly and a move to a different site can take care of the problem. You can pick up a tester locally or online pretty inexpensively. I keep one in the trailer. There are also ones that show the AC voltage, but are more expensive and more difficult to find. You can find one like the one in the link to Amazon at most hardware stores.

On edit:

Twinkie is exactly right. He just beat me with the post. The testers we are talking about are the same. He is especially right about the danger involved. Unplug the trailer till you figure out what is going on. If you don't feel competent, this would be an excellent place for professional help. It could be some of the best money you ever spent.

[DaveFL]

When I plugged in at home with an extension cord that the ground pin was missing my cheapo detector looked the same, two green lights showing, positive and negative not reversed but it didn't show that the ground wire wasn't connected. From this I now know that if the chassis is grounded to the ground a cheap detector won't show it.

[Airdog]

I had a similar problem with my 72 Sovereign. I could feel current especially when hooking up the water supply and the ground was damp or wet. I removed and cleaned the ground for the power supply to the frame and that fix my problem. Remove the ground, grind the metal shiny and replace with a clean new bolt and put some fresh paint over it. It might be what some of the others said, but I would check the easy and cheap things first. Good luck, Bill

[pbearsailor]

If your '57 looks like mine did inside the walls, I would sure recommend forgetting that original 54 year old mess and starting over. If you're gutting it anyway, don't waste time on the old wiring and just run some lighting off a good extension cord while you're working. Run a new electrical system when you get to that point.

cheers,
steve

[movinair]

Thanks everyone for your advice. I am going ahead with using extension cords while I disassemble. I'm going to plan to just re-wire everything.

While taking out the fridge, I notice that the 120V outlet was wired with the ground to the aluminum frame? Shouldn't it have a ground wire that goes to the chassis or to the fuse/breaker box ground terminal?

The 120V outlet that the AC/DC converter is plugged into doesn't have a ground at all? Shouldn't it also be grounded to the chassis or fuse/breaker box?

Am I right that when re-wiring, the trailer will need at least two 120V outlets, one for the converter and one for the fridge to run on shore power? Is it advisable to make a third to use with standard items such as plugging in a laptop or charging a cell phone?

Steve - do you have any kind of diagrams for the wiring of your '57? I can't find any manuals or diagrams of any kind, and would sure like something to follow.
again many thanks folks,
Matthias (Movinair)

[pbearsailor]

Originally Posted by movinair

Steve - do you have any kind of diagrams for the wiring of your '57? I can't find any manuals or diagrams of any kind, and would sure like something to follow.

Matthias, there weren't any manuals for back in those years, other than just a small general booklet, along with individual booklets for water heater, fridge, etc. The original system was just so basic, you'd probably not really want to follow much of it anyway.

My '57 had no 12 volt system other than one overhead light powered by the tow vehicle. The AC was all 2 wire with wire nuts and electrical tape holding things together. No boxes on the outlets.

For my redo, I just planned out what I wanted to power and where it would be located and developed a plan from there. Other than a bunch of 110 volt outlets, my trailer is mostly 12 volt now with all LED lighting, solar, and golf cart batteries.

cheers,
steve

[SpaceEgg]

Originally Posted by movinair

However when I went outside to try to unscrew the banana wrap*, and touched the metal screws, I got bitten by an electric shock. Does that mean I have a wire that is grounding out somewhere that shouldn't be? How can I find it?

any help greatly appreciated.
matthias

I have a similar problem with my 59 Tradewind. A couple of brief points...

1) Search the Airstream electrical forums for "floating ground". I think that's the technical term for they type of electrical system a trailer has. Since the only part of the trailer that actually touches the ground are non-conductive rubber tires (and maybe your hitch) it's hard to actually wire a good conductive "ground wire". So you must wire the ground wires within the trailer to the grounded wire in your 120VAC fuse box which then safely returns any excess electricity to the shore power. If you instead ground your outlets to the trailer shell (like a lot of 12VDC systems do), it can become a high-voltage short-circuit back to the trailer fusebox and electrify the entire shell.

2) Re-wiring might be a lot of trouble. Best to accurately discern what and where the problem is before you try to fix everything. Purchase or borrow a reliable voltmeter and troubleshoot each outlet, the fusebox, and the trailer shell. You may find the system wiring is in better shape than you thought, but needs a little safety tweaking, or just a better fusebox.

3) FYI - I have 5 outlets in my trailer - one for fridge, one up front in dinette, one above each twin bed and one below kitchen sink (previous owner had an electric hot water heater). I also have those old 2-system AC/DC lights with an optional AC plug above each twin bed, above the kitchen sink, and above the bathroom sink. Apparently, someone decided they needed electricity EVERYWHERE!! But it's rather convenient.

Good luck. I would love to hear what you discover is the matter, as I still need to address this issue myself.

[Aviator]

I believe the tongue jack is the grounding point for your trailer. It is the only metal that actually touches the earth.

[TG Twinkie]

The tongue jack is not the grounding point. You could and would lose the ground if you put a non conductive block under the jack. The grounding point is the power source. In all of the devices (ie outlets etc) there is a bare wire which is ground. All of the bare wires are connected to a ground buss in the power panel of the trailer. Don't confuse ground with neutral. The neutral should not be grounded inside the trailer.The ground buss is connected to the ground wire that attaches to the trailer skin or frame inside the trailer, it is usually a #6 or larger solid wire; it is also connected to the ground wire in the power cord for your trailer which is in turn connected to the ground buss in the power panel that you get power. This is where the ground is finally connected to EARTH ground. If everything is wired correctly. All of the above is for the 120 volt AC power in your trailer.
Not to be confused with the DC wire called GROUND, this is actually the DC common for all of the 12 power in the trailer as well as the TV ground for the exterior lighting. In the DC circuit there is current flow through the skin of the trailer. It is 12 volt DC and is not a shock hazard. If you take notice, most if not all of the DC devices in the trailer have one wire. It takes 2 wires to make a circuit. In the DC system the trailer body and frame is the second wire. The skin of the trailer is connected to the negative terminal of the battery; sometimes thru a 50 amp fuse for the interior DC system. The exterior DC lighting circuits are protected thru the fuse panel in the TV and the ground (common) is connected to the frame of the TV as well as the trailer.
The automotive industry made a mistake years ago when they labeled the "common" side of the DC electrical systems ground. That is my opinion. But it's too late to change it now. It just adds confusion to the mysteries of electrical systems. After all, IT'S THE SMOKE IN THE ELECTRCAL SYSTEMS THAT MAKES THINGS WORK, BECAUSE WHEN YOU LET THE SMOKE OUT IT DOESN'T WORK ANYMORE. LOL

[mello mike]

TG Twinkie,
For home wiring, whenever you wire an 110v outlet to a metal box that box acts as a ground so an additional wire isn't needed for the ground. Couldn't the same be said for an aluminum Airstream?

[Bill M.]

you should be running both the trailer and any power tools used on a GFI circut. If the GFI kicks off when you plug it in you have a problem that should be fixed.

[Zeppelinium]

Originally Posted by Airdog

I had a similar problem with my 72 Sovereign. I could feel current especially when hooking up the water supply and the ground was damp or wet. ...

In the 70's Airstreams (and maybe others) you have another path to put power on the shell--the "reversed power light." This light should be removed because if the RV park has reversed power and also has an open ground, then the shell will have power through the filament of the bulb and nothing will blow, except you, of course, when you step down onto wet ground.

For home wiring, whenever you wire an 110v outlet to a metal box that box acts as a ground so an additional wire isn't needed for the ground. Couldn't the same be said for an aluminum Airstream?

Mike, the answer is "maybe." The metal box has to have a ground wire to the power system ground and the local ground stake. In the "old days" power wires didn't have the third bare ground wire--ground was supplied by the metal box and the protective flexible metalic sheath that was around the power wires. You cannot rely on this method today, especially if the metal box is part of a pre-60's house installation.

Zep

[TG Twinkie]

The neutral wires within the trailer should not be grounded. Only the ground wire (the bare or green wire) is grounded. There should be two terminal strips within the 120 volt AC panel. One is the Neutral (white wires); This terminal strip should not be grounded, it should be isolated from the metal box with some type of insulating material like bakolite. The other is the Ground (bare wires); at least one of these wires, preferable one of the larger wires should be connected to the skin and/or frame.
If you are getting shocked by the trailer skin, the chances are good that the neutral and hot wire are reversed at the shorepower outlet or in the shore power cord and the neutral wire is connected to the skin and the earth ground does not exist. If the hot and neutral are reversed and there was actually a ground path, the circuit breaker would trip when you plugged in the trailer.
All circuits should be tested with a circuit tester like the one I have attached here. I have also attached a photo of the proper receptacle and cord end for the shore power cord.

[mello mike]

TG Twinkie,
I guess I didn't word my question properly. I'm not asking if it's okay to cross connect the ground and neutral (I know you shouldn't do that). My question is: To ground a modern 3-pronged outlet do I need to connect a bare ground wire to the ground screw then connect that wire to the frame? Or does the fact that I screwed the outlet into the metal interior skin satisfy the ground? (Note: The grounding screw is attached to the same metal plate that the bottom mounting screw goes through).

[TG Twinkie]

Here are a couple of ways to ground the device and the box. The ground wire you use should be part of the Romex cable where one end goes to the power panel and is connected to the ground bus. Black to circuit breaker; White to Neutral buss.

[GeocamperAS]

Why is the 120v ground attached to the trailer shell?

Although current should never flow through ground if all 120v items are working properly, In the event of a short to ground in a device that is plugged in, I would want the current through the ground wire to only go the the campground power source NOT through my trailer shell. #1 The shell will be live. #2 the 120v could feed into my 12v system through the 12v neutral aka ground and cause problems.

[TG Twinkie]

As far as I know all the boxes in the trailer are non metalic, therefore there is no place for the ground wire to contact the skin. I think the only place the AC ground wire would be attached to the frame is at the panel, usually a #6 wire goes to the frame from the ground buss in the panel. That way if a hot wire AC comes in contact with the skin, it will be taken to ground and the breaker should trip instantly.