The book, RV Electrical Systems, which you can find on Phred's Poop Sheets (google that and look for his electrical info), is what I used. Essentially, the physical aspect of the electrical wiring is the same as household electrical wiring.
The electrical service line comes into the breaker box ("mains breaker" type box, with the MAIN BREAKER, not a "mains lug" box with no main breaker). 30 Amp installations use one 120 VAC supply line. 50 Amp installations use 2 120 VAC supply lines. (You could actually hook up a 240 VAC circuit in your bus if you had some kind of power equipment that required it.)
The incoming ground wire gets wired to the breaker box on the grounding lug strip. The ground wire should also be wired to the chassis of the bus. That is very important. The ground lug strip is the one that is physically connected to the breaker box itself. If you use regular household "Romex" cabling, the ground wires will all be bare copper wire. That is fine. Just be neat with your wiring, and don't let them touch any of the hot or neutral wires where they might make electrical contact with the tips of the wires in the breaker box. (Boxes are designed to make this difficult anyway.)
The incoming hot wire(s) gets wired to the breaker box at the main circuit breaker.
The incoming neutral wire gets wired to the breaker box on the neutral lug strip. The neutral wiring should be "floating", that is, not connected to the ground wire or the chassis (which is a ground) anywhere in the bus. THIS IS VERY IMPORTANT. The neutral lug strip is the strip that is insulated from the breaker box, usually on raised insulated posts, and with a shielding strip that will keep the neutral wires from sticking through the lug strip and contacting the breaker box.
There is a simple formula for Watts/Amps/Volts. Watts are Volts times Amps. You sometimes see them referred to as Volt-Amps. Volts are Watts/Amps. Amps are Watts/Volts.
There is a tenfold difference in AC and DC voltage, so AC Watts and DC Watts are different because because they have different voltages. I didn't say that exactly properly, but here's how it works:
120VAC * 10 AMPS = 1200 Watts
12VDC * 10 AMPS = 120 Watts
120VAC * 1 AMP = 120 Watts
120VDC * 10 AMPS = 120 Watts
If you find the Wattage of an item (reefer, tool, pump) and know its operating voltage, you can determine how many Amps a circuit will have to carry in order to run the item properly.
Reefer @ 1500 Watts on a 120 VAC line uses 12.5 AMPS for continuous
operation. Some equipment uses as much as 3 times its running Amperage to start, particularly equipment with motors in it. This surge demand has to be accounted for in designing a circuit.
Wire sizing is important. A wire sized to carry, say, 20 amps on a 20 amp circuit for the example of the reefer above could run the reefer fine at 12.5 Amps of current. It could also handle the 37.5 Amps that the reefer requires to start its compressor motor on a momentary basis
, but it could not handle a continuous
load of 37.5 Amps -- it would heat up and maybe cause a fire.
The book I mentioned goes into great detail about all of this, circuits, wire sizing, etc. (as do other books, but I have read the one mentioned above).
Circuits are very simple, essentially, even in RV or household wiring. They work just like the Radio Shack kids' electrical experiment circuits, only the wires are longer -- and the goal of making them is NOT to see how big a spark you can make!