I need a ground...

[cpaharley2008]

I'm in the process of installing red minature led lights on several switches to indicate power on condition. The main disconnect was easy, I was able to tap into the main 12v ground behind the converter. Now I'm installing one on my 12v heat pads, under my bed for my tank heaters. I have found the source/juice for the light on the pad switch. But now I need a ground.
Can I use the propane copper tubing? what about a nearby 120v outlet with a metal box? Both of these make the bulb work. Would either of these be a problem? I have access to some white,red and black 12v wires but my led wire is really small like 24 gauge and I do not think those "taps" will work with such small wires. If so, which is ground, the red or white or black? thanx

[Jim Bennett]

Originally Posted by cpaharley2008 (jim)

If so, which is ground, the red or white or black? thanx

Neither is ground. The red is positive, the black is negative. The negative is grounded at the converter only.

[cpaharley2008]

ground is negative, it works when I attach it to a brass elbow on my water line, also when I touch it to my propane line, all of these are grounded. I feel safer touching a water line. Now to see if it works when there is no water because I think the water is making my ground by connecting the brass elbow to a common ground. The draw is minimal, .03 milliamps for the led bulb. I'll look for a better negative tomorrow and it is only on when I turn the pads on.

[Vermilye]

While the chassis & related metal are grounded, it is not a good idea to use them in place of a negative wire. It works, but running a wire to the location of your negative wires at the converter is better.

I would definitely not use the propane line. While unlikely, if you happen to break the electrical connection of the propane line at a fitting, the resulting spark could ignite the gas.

[cpaharley2008]

tomorrow I'll try to tap into a black wire using a thicker wire and then fuse the smaller wire to the thicker one. I've got bowling tonite and the temps are dropping to 40's so can not do anymore til then.

[Jim Bennett]

Originally Posted by cpaharley2008 (jim)

ground is negative

Not exactly. Yes, the negative is bonded to ground, but the ground should not be used as a negative conductor, as Jon said. It has been done in some cases in the past, but is not a good idea. There are systems out there that use a positive ground too.

With DC wiring in our trailers, you really should not consider or concern yourself with the ground. The circuits work with positive and negative conductors back to a battery. Things would still work fine if the ground was not connected to the negative at all. Grounding all pieces of metal will prevent the metal from becoming "hot" and being a shock hazard.