2 questions

[rama777]

Is it ok to run more than one ground wire to the same piece of metal? They are on different screws of course, but on the same metal. Also, I am about to test my 12 volt system but I've removed some things from the wires like the water pump and some lights. So some wires have elelctrical tape on the ends but they aren't hooked up to anything. Will this cause glitches and shorts or does it matter at all? Thanks for your support.

[markdoane]

I think you can run as many as you want. For ground wires, I like to ttach to a frame bow and use anti-corrosion paste, the kind that is used for connecting aluminum wires.

Taping off the ends of wire should be fine to keep them from shorting, I use wire nuts for a little more insulation.

[rama777]

Does it really matter at all where and what type of metal you put the grounds on?

[Jim Clark]

Originally Posted by rama777

Does it really matter at all where and what type of metal you put the grounds on?

Well yes. Example. The engine in a car is mounted on rubber motor mounts to the frame of the car. If you ground your battery to the frame the engine is not grounded unless you have attached a grounding strap from the frame to the engine. You have to do a little thinking about what and where you place your grounds. I clean the metal very well and use electrical grease when I ground.

I had a boss who had a boat, the boat battery had a ground to the engine and a hot lead. My boss just couldn't figure out why his lights didn't work. It was simple he connected his ground wire to the fiberglass hull of the boat.

Jim

[Fyrzowt]

I had a boss who had a boat, the boat battery had a ground to the engine and a hot lead. My boss just couldn't figure out why his lights didn't work. It was simple he connected his ground wire to the fiberglass hull of the boat.

Funny story, but a great lesson.

[kaffe_1477]

Best method to ground, in my opinion, is to use self tapping screws into the frame. The anti-corrosion paste is a good idea too.

Actually now that I think about it...the whole trailer would be a ground if the frame is grounded. Right? Aluminum is a great conductor and as I think about it, isn't the frame and shell all attached? So would it really matter where you grounded it?

Then again...passing current from carbon Steel (the frame) to Aluminum would speed up the cathodic corrosion of the Aluminum where they meet. This is not a good thing at all.

[sander17]

I would recommend the steel frame. Aluminum is so chemically reactive that you never see bare metal in air. It is always coated with at least a one molecule thick layer of aluminum oxide. That is why aluminum electrical wiring should always have the special paste used to keep the connections from overheating. The iron oxide on the steel conducts electricity well enough to prevent heating if current flows thru it.

[markdoane]

I wouldn't use the steel frame as a ground. First, there isn't anything electrical that uses the frame as a return path. The brakes have a separate ground wire. OK, maybe the power jack. Run a separate ground for that too.

Don't knows about current models, but my old tradewind doesn't have any good steel-to-aluminum connection that doesn't have plywood (or paint) between.

The electrical devices that need a good ground are the running lights and brake lights, maybe the interior lights. They're all mounted on the aluminum shell.

My recommendation: use the aluminum.

[safari57]

Suggest rather than use a battery to test the 12v, system before hooking up to your converter or inverter, that you use a battery charger. A suggestion I got from a car rewiring firm years ago when redoing one of my hotrods. You are less likely to damage anything, including your battery. Once everything checks out okay, then put the battery in and hook up the converter/inverter and you know that everthing from the battery out is already working okay.

Barry

[Minnie's Mate]

Originally Posted by Jim Clark

I had a boss who had a boat, the boat battery had a ground to the engine and a hot lead. My boss just couldn't figure out why his lights didn't work. It was simple he connected his ground wire to the fiberglass hull of the boat.

Jim

Similar thing happened at the press conference when Chevrolet introduced the Corvette back in the '50's. They couldn't get the engine to start...or even turn over. Seems they used conventional wisdom and grounded to the car body...forgetting that it was fiber glass. A quick change in the ground to the chassis and it started right up. They were quite embarassed as they were introducing this great performance car that wouldn't even start, but once it did, man it just hasn't stopped since!

[wkerfoot]

Originally Posted by markdoane

I wouldn't use the steel frame as a ground. First, there isn't anything electrical that uses the frame as a return path. The brakes have a separate ground wire. OK, maybe the power jack. Run a separate ground for that too.

Don't knows about current models, but my old tradewind doesn't have any good steel-to-aluminum connection that doesn't have plywood (or paint) between.

The electrical devices that need a good ground are the running lights and brake lights, maybe the interior lights. They're all mounted on the aluminum shell.

My recommendation: use the aluminum.

Mark,

Don't you have bolts connecting the channel to the outriggers? I realize that this will have the plywood floor between but still a good connection from aluminum to steel.

Bill

[markdoane]

Bill,

Yes I do, but they are the first thing to corrode and build up a layer of oxide. That, and the fact that they are located in a pretty inaccessible location for R&R. And originally the outrigger was painted. Makes it a pretty iffy connection in my opinion.

All of these conditions are prohibited by the NEC.

[TomW]

Originally Posted by markdoane

I wouldn't use the steel frame as a ground. First, there isn't anything electrical that uses the frame as a return path...OK, maybe the power jack. Run a separate ground for that too.

Don't knows about current models, but my old [59?] Tradewind doesn't have any good steel-to-aluminum connection that doesn't have plywood (or paint) between.

The electrical devices that need a good ground are the running lights and brake lights, maybe the interior lights. They're all mounted on the aluminum shell...

Jumping ahead to quasi-modern-day , here are a few observations on my '67 Airstream as it was delivered to the original owner:

The Univolt had a 10 gauge copper wire coming off the the negative terminal which was wrapped under one of the elevator bolts which tied the aft shell to the aft-most frame member spanning between the two C-channels. Thus, as delivered from the factory, the shell was tied electrically to the frame. The wire then continued to the 12 volt distribution panel.

Originally Posted by Minnetonka's Best

...maybe the interior lights...

All of my '67's 12 volt interior power users are all wired with two conductors; The shell does not help electrically for anything located inside, but Don nailed it as far as the running & brake lights are concerned.

Like Don, I don't know about current models.

Tom