12v Wiring

[beyond]

Hey all,
I'm done with the floor finally and beginning to wire out for 12v (110 to come later). I've received conflicting views on whether 12v has a ground, and when/if the ground is installed for 12v.
Need to Ground 12V DC system? - Boat Design Forums
I've attached two graphics portraying what I am trying to do. The small solid blue squares are individual lights, and the faded squares around them are complete circuits to be controlled by one switch each. The squares down the middle are the ceiling vents. 110 as noted prior will a completely separate system.
To start the process can I simply run my positive and negative to each location? or worry about ground at this time?

Thanks!

[3 Dog Nite]

I would choose to run a ground (neg) wire to each fixture or outlet. Run 1 wire per circuit, right along with the hot (pos). Don't run just 1 wire for everything. That lone wire would have to carry all of the amps & be a larger gauge. Be sure to run them through rubber gromets so the vibrations don't wear the wire's insulation & cause a short.
I would not ground out the fixtures to the chassis like in a car.

Ricky

[wkerfoot]

Like Ricky,

I ran a ground wire to all fixtures, 12V outlets and fantastic fan locations. I did not run a ground to the running and tail lights. I used two wire 12 gauge for all my wiring which needed a ground.

Bill

[beyond]

Bill and Ricky,
Would that mean that there is the positive, negative, and ground to all fixtures, 12v outlets, and fan locations? I am thinking that negative and ground are the same. Yes?

[overlander63]

Originally Posted by beyond

Bill and Ricky,
Would that mean that there is the positive, negative, and ground to all fixtures, 12v outlets, and fan locations? I am thinking that negative and ground are the same. Yes?

Two wires for 12 volts. Black is power, white is ground.

[wkerfoot]

The trailer is negative ground, just like the tow vehicle, unless you have an old British car. Black is positive and white is negative or ground

[TG Twinkie]

It would make things soooo! much simpler if everyone would refer to the -negative wire in the 12 volt circuit as "COMMON". I know auto makers call it ground, trailer manufacturers call it ground. But it's NOT ground. It is common to all of the devices in the trailer and TV. But it is not grounded to EARTH Ground. I would run 2 wires to everything if I were to rewire my unit. The reason AS and others don't is to save money.

[uwe]

I suggest that your Airstream's shell and ribs make a really nice ground wire. I find it redundant to run separate ground wires to light fixtures and pumps etc. UNLESS they are mounted in fiberglass end caps, or otherwise against wood or non-ferrous surfaces.
It is of paramount importance, though, that if you are using the shell and frame as a ground ( negative potential) , to make absolutely sure to have a very safe and solid negative battery connection to the shell AND frame. If you follow the Airstream original wiring diagrams, you will see that the negative wires ( white ones) always end up being grounded to the shell at some point.
Having said that, I use heavy ground wires to all motor driven DC devices, to avoid flickering lights when fans or pumps jump into action. In any event, it does not hurt to run separate grounds to each fixture, but I find it unnecessary.

[63air]

I second using the shell. The more wire you you run , the more you increase chances for future problems.

[Sheridan]

On the other hand, if there is a ground problem, the fix is located at a central point where it would be easier to diagnose and repair.

[Minno]

Hey Beyond,

If you're running multiple 12 volt circuits, then I'd recommend using a different color wire for the positive wire on each circuit. There are plenty of colors available - black, red, blue, purple, orange, green, brown, etc. Then it's easier to keep track of what wire is what circuit and fuse. If you have trouble down the road, or want to add another light or whatever, you'll know which circuit it is by the color of the positive wire. Keep all the ground/common/negative wires white. Also, make sure the wire gauge matches the load and fuse you plan on using it for.

Chris

[toastie]

These are the diagram's that I followed. Ran a ground right to tongue, tongue to a grounding bar, bargman cable ground to grounding bar, electric brakes and battery to grounding bar, complete design control. Everything is working perfect..........toastie