Guage ?

[KZGoodchild]

Hey all, geting to wiring trailer now! While Polishing on too hot days to be inside..... anyhow, have run most 12 v wires, but forgot to string up grounds.... I think I read somewhere that I can string three lights (conventional) on one ground wire. My problem is can i or should I use a smaller guage wire, or same as the "hot" wire? I have used 14 ga up to now, and am considering 18 ga for ground////???? Also, Should I run this to the frame, wall "joists", or back to battery negative ???

[HiJoeSilver]

Your 12v circuit doesn't really have a ground, it has a positive and negative to each fixture. The system does get grounded to the frame usually from the fuse panel to the shell or frame or both. Which means you can actually use the frame/shell for a negative path, but that can cause problems.
Back on point the wires feeding the fixtures should be the same going to and leaving the fixture since they both carry the same amount of current, so use 14 gauge on both. The negatives should run back to the battery/fuse panel.
If you have positives and negatives and are thinking the fixtures need a ground as well(like 120vac) they don't.

[ITSNO60]

What he said^^^ Undersized ground wires can overheat and in extreme cases start a fire. When the wires are the same size and the terminations are solid they won't overheat because the fuse on the positive side will melt first. Since there is no fuse on the grounded (negative) side if you use skinny wire it can get hot enough to burn without the fuse on the positive side melting.

[mimiandrews]

All electricity flows through both wires. Make them both adequate size.

12 v. is not a "just in case" ground like one finds in AC circuits, it's part of the primary path.

[rmkrum]

A better way to think about 120v AC circuits is as follows:

Black wire is the "hot" or 120 volt supply lead.

White wire is the "neutral" or 120 volt return lead.

The green or bare copper wire is the "safety earth" or ground lead. This is used to provide an alternate return path in case the hot wire gets shorted to the case of an appliance. It's really there just to blow a fuse or trip a circuit breaker.

The 12 volt DC wiring has a positive supply wire. Color varies a lot for convenience of tracing circuits.

The negative supply is either a wire the exact same wire gauge as the supply wire, or the body and frame of the vehicle.

Wire sizes are yet another discussion. Rule of thumb is for a 20 amp circuit, 12 gauge wire. 15 amp circuit, 14 gauge wire. Other amp ratings, there are wire size tables that tell the tale. Wire gauge has nothing to do with the supply voltage. It's all about current capacity.

[KZGoodchild]

Alright so I'll get another 500 ft of 14 ga, but, if i have a 45 amp WFCO Power converter but am using only 14 ga wire, is that too small a gauge ????

[HiJoeSilver]

Originally Posted by KZGoodchild

Alright so I'll get another 500 ft of 14 ga, but, if i have a 45 amp WFCO Power converter but am using only 14 ga wire, is that too small a gauge ????

It depends which wire you're talking about. The wire from the converter should feed a fuse panel, through the fuse panel it should then connect to the branch circuits and battery. The wire that connects the converter to the fuse panel should be a minimum 8 gauge for 45 amps. The battery cables should be this size minimum as well for 45 amps, unless you have a large inverter then you'll need bigger wire connecting the battery and inverter.
When the circuits branch out from the fuse panel each branch will(should) take a portion of current. In your case each circuit should be set up so it takes 15 amps of load max with everything on in that branch on, because you're using 14 gauge wire.