Installing Generator

From what I see, a prewire needs to have five things:

1: Some type of vapor barrier between the genset and the inside. Usually metal flashing.

2: Some way to mount it.

3: An ability to tap into the fuel tank at 1/4 level.

4: A way to route the exhaust safely, preferably using the Onan resonator.

5: The electrical output, including a remote start switch, and maybe even a generator controller.

From there, the install should be done by people who know what they are doing. If installed right, with acoustic insulation on all but the bottom (the bottom doesn't get insulation due to possibility of fuel spills getting absorbed by it), shock mounts, engineering to handle vibrations on the exhaust, fuel, and electrical lines, and finally proper clearances for air to come in and out, it will be pretty quiet. Without this done, the Onan can be quite loud and vibrate the coach like a Magic Finger bed.

Typically Onan 4000 in a C or 30A Class A. I've seen Onan 2800 but only in truck campers. Get the mounting dimensions and verify that 4000 will fit the space. I added an older Onan, the "4.0 RV Genset" to an older coach that was also pre-wired and it went pretty well.

I, personally, haven't looked at our RV gas tank to see how the genset fuel tap looks or connects. If the coach is new enough to be fuel injected, you can't tap into a fuel supply or return line near the genset. Must run fuel line from the tank.

If it is prewired, great! But don't forget it will need a fuel line from the gas tank and you will have to have a frame built and welded into place in addition to the cost of the genny.

Thanks, I am looking at a C Class I originally had a 31 foot last year and I am now looking at a 23 foot as I moved to the city and need a smaller one to fit in driveway and i need a generator, the one I am looking at is a not bad price but does not have a generator. I was told it was prewired I just want to ensure that a aftermarket install is as reliable as a generator initially installed generator. I would assume a Onan 4000 would be required?

Onan generators are very reliable if properly maintained and are what most RV manufacturers install in their rigs. If the RV is factory prepped for a generator, installation is relatively easy as long as you use the proper type of Onan generator as they do have different methods of dispersing exhaust. A 4000 watt Onan is normally installed for a single AC rig , or a 5500 watt Onan for a rig with 2 AC units.

Also which fuel type will be used, propane, Diesel, or gasoline? Portable generators are not designed to run in the confined space of the generator compartment but they can be stored there and removed for use once you get to your campsite. Portable generators are a popular choice for many as they don't need much power and don't want to overspend on an item they may only use sporadically throughout the year.

A 2000 watt portable generator will run most items including microwave but no AC. A 3000 watt portable generator will run most single AC units, you can parallel two 2000 watt portables for 4000 watts, capable of powering your entire rig. Honda, Yamaha, and Champion inverter generators in the sizes above are popular choices here on the forum and all have a good reputation for customer service.

Aftermarket, what particular unit are you referring to. Not the tubular framed models I hope. Unless it's one designed to be mounted under a coach you will not be able to quiet it down to a level that would be liveable.