I am rewiring my 85 burro. I decided to leave the previous 110V wiring in as it works ok, however, when I was taking out the 12V wiring, I noticed the 110V had a large green wire for the ground. Is this really necessary? Isn't that what the ground plug is for?
I also remember seeing someone say that this wire should be attached to the frame. But someone else said the frame is the worst place for a ground. Confused to say the least. I tried to use the previous grounds that went to the frame and have had nothing but heartache. Any suggestions?
Your confusion arises from mixing up "ground" and "return."
Ground is a term for safety connections. Both the AC and the DC should be grounded to the trailer frame at one point each. This ensures the frame stays at the same voltage level as the earth. The AC ground (the green or bare wire in AC circuits) is connected to earth at some point.
Return is a term for a part of the electrical
circuit. In an electrical
circuit, one wire goes to each load to supply current to that load, another wire goes to each load to return current to the source. All the current through a load is carried by the two wires, none of the current should flow through ground.
In AC wiring, the wire supplying current to the load is called high or hot (black), the wire returning current from the load is called low or neutral (white). The safety or ground wire (green) should not normally have current flowing through it; when current does flow through ground it is because of a fault in the circuit.
A ground fault may mean that your body has completed a circuit between hot and ground (i.e., in your house you get into the tub with a hair dryer running in you hand). Some of the current supplied by the hot wire is now flowing through your body through ground back to the source. This means that the currents in the hot wire and the neutral wire are imbalanced. This imbalance is sensed by the ground fault circuit interrupter (GFCI) which interrupts the hot side of the circuit in a fraction of a second, saving your life.
In DC wiring in our cars or trailers, the wire supplying current to the load is called +12 volts or positive, the wire returning current from the load is called -12 volts or negative or 12 volt return. Wiring colors for DC are not as well defined as for AC.