Any enclosed camper with wheels, used for fun or getting away from regular lifestyle, could be called a recreational vehicle, or RV. Normally, though, the term "RV" is used to describe an A, B or C-Class motor home. Travel trailers which are towed and camper tops which are attached to pickup truck beds do not typically have generators fitted by the manufacturer. A and C-Class RVs usually do, and B-Class RVs usually have a cargo bay preconfigured to have one fitted as an option. Wiring an Onan generator that is manufacturer-installed, or installed into a generator-ready bay, is a straightforward project.
Install the wiring harness which allows the generator to function. Decide whether a remote switch to start and stop the generator is important, or whether using the switch on the generator's fascia will be adequate. If a remote starter/stop-run switch is required, run a twin-core 14-gauge wire from the generator to the location of the switch, and attach a rocker switch according to the switch manufacturer's instructions. Depressing the top of the rocker switch will cause the generator to start; depressing the bottom of the rocker switch will cause the generator to stop. The switch will return to a central, non-functional position when not depressed. Connect the twin-core wire to the terminals on the generator control panel, which will be clearly marked, using spade connectors.
Install the wiring harness which allows the generator to function without a remote starter facility by connecting a live wire directly to the generator control panel. Typically the generator's ground will be made through it's mounts to the RV's chassis. Observe Onan's installation instructions for the live wire, which will usually be attached to a threaded captive bolt. If this is the case, attach an eyelet terminal to the end of the wire from the dedicated battery, and secure it in place on the threaded captive nut using a lock washer, a conventional washer and then a bolt. Starter disconnect, fuel pump control and electric choke control will all be automatic.
Install the wiring harness which transfers electricity from the generator to the RV. Run wire from the location of the generator to the inside of the cargo bay set aside for the storage of the shore power cord. Use type-UF wire rated for the amperage created by your generator. At the generator end connect the live wire to a clearly-marked insulated threaded captive bolt using an eyelet terminal secured in place on the threaded captive nut using a lock washer, a conventional washer and then a bolt. Connect the negative wire to the negative terminal in the same fashion, and the earth wire to the earth terminal in the same fashion. At the end in the cargo bay connect the wire to an outlet prescribed for the amperage demand of your RV and the corresponding amperage delivery of your generator, either 30 or 50 amps. Carefully observe the outlet manufacturer's instructions regarding polarity.
Install a starter battery dedicated to the generator, so starting power does not rely on and/or deplete the coach or chassis batteries of the RV. Wired correctly, the battery will be charged by the running generator, just as the chassis battery is charged by the chassis engine. Consult the generator manufacturer's literature concerning battery capacity; typically a ride-on lawnmower battery will perform adequately. Locate the battery where it will not be subject to excess heat or undampened vibration. Fit it in a proprietary battery tray, and secure it in place with the strap or metal clasp included with the tray. Use black colour-coded 6-gauge wire to connect the negative terminal to ground, and use red colour-coded 6-gauge wire to connect the positive terminal to the marked terminal on the Onan generator, typically on or near the starter motor.
When routing wires in an RV, always use plastic zip ties to secure the wires where they will not contact hot components or moving parts. If the wires pass through a hole drilled to accommodate them, use a rubber grommet to protect the wires from abrasion.
Electricity is dangerous. Make sure to disconnect the negative cables of any batteries in the system you are working on, and make sure the generator is not running when wiring the 120-volt components of the system.