Onan 10K generator for home use-removed from the rig.

The 120/240 output can be wired onto a standard range receptacle or wired into a transfer panel in the house. Transfer panels are available at many big box hardware stores.
On like this
Transfer panel

A generator interlock kit for his main circuit breaker box costs less, is easier to install and much more flexible.

This really has nothing to do with getting the generator running but it will be the next step.

To get the generator running, your friend will need a 12V battery and an AC powered battery charger as the generator most likely doesn't have a battery charge circuit built in. (It's an option on at least some of the Onan RV generators, rarely fitted.) Probably it's unnecessary to worry about the other wires for the inside remote control and hour counter and pilot light for basic operation; the start and stop switch on the generator I think should work just fine with them left unconnected. Of course, having a remote panel would probably be more convenient.

I'd think an old but not completely dead car battery, or a not old riding lawn mower battery, would suffice for starting the generator.

The Onans use a bunch of latching relays. You will need wiring diagrams from ONAN not Cummins. I take it this is a diesel.

Start Run circuit
Safety shutdown circuit
Both are needed.
Onan is famous for using 3 colors of wiring and ID numbers on the wire.

The plastic rings around wires are current sensors. Do not remove. Anything with a plug and socket should be unplugged and doused with Caig DeOxit D100 then replugged.

You need a ganged 240 breaker near the machine.

The generator must be enclosed with ventilation. It cannot survive getting wet.
Long term storage plug the exhaust with a rag. I strongly recommend a RAcor fuel water filter. If the unit has glow plugs I also recommend a push button over ride if temps approach 0°F.

Keep the unit high enough off the ground to make oil changes easy.

Here's a link to a YouTube video of a Onan Quiet Diesel 10kw generator:
https://www.youtube.com/watch?v=p3nx7OIExHI

Apparently all you need is a battery and fuel supply. The remote start panel should not be needed.

Thank you guys I appreciate all your good help.

MEXICOWANDERER wrote:
The Onans use a bunch of latching relays. You will need wiring diagrams from ONAN not Cummins.

The generators are still branded as "ONAN", but the Cummins site is where you need to go for manuals, etc.

Cummins Generators & Power Systems - RV Generators

cal an electrician.

Thank you Cavie. I know he intends to get an electrician for the house end of it. Maybe electricians might be pretty good at getting the genny set up to go also. He actually has a house and a mobile home next to it, and he was thinking it might be able to power both if it's set up right. This is in the mountains of Oregon, and when the power goes down from storms or fire it can be out a long time.

would need full model and spec number to be certain of information, but can be done for sure. If the genny is a ONAN Quiet Diesel, then it has 120/240V, 1 phase power output, as do most residential services. There are many considerations to apply here, but are far beyond the scope of this forum. Special consideration has to be made for a mounting framework, as all the cooling air intake and discharge are in bottom of these generators. An ONAN installation manual would be helpful. I have helped someone do this before, and it turned out to be very nice project.