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Posted by D Sherman [98.225.32.22] on Sunday, December 04, 2011 at 14:22:55 :
In Reply to: OT diesel generator posted by Bill in CO [67.135.131.130] on Sunday, December 04, 2011 at 14:00:40 :
I used to use an Onan 6.5 kW 2-cyl civilian generator all the time, which was identical to a 5 kW military unit that you're probably looking at. A guy gave it to me for free because it had a hole in a piston and was all carboned up. It was easy to start and reliable and didn't use much fuel. I don't use it any more because for construction nowadays I like to use an inverter and a battery so I can leave it on all the time without making noise and burning fuel.
As for power, 5 kW should be plenty to run a home so long as you don't run an electric range and water heater. In a pinch you can run the water heat off of it, and you can run probably half of the range, but it's not something you'd want to to long-term. I assume you're not even thinking about powering an electric furnace or baseboard heaters. 5 kW is more than enough for all the non-heating loads in a house and for running normal shop tools since you don't turn everything on all at once. The utilities figure the average load of a home at 2-3 kW.
I expect your well pump is probably about 1 HP, which is roughly 1 kW, conservatively figured. It's not going to be more than 2 hp which is still easy for that unit. Centrifugal pumps are an easy-to-start load because the pump has no resistance at zero RPMs. 240 vs 120 volt doesn't matter. I always ran my table saw off 230 with the Onan.
In general, with any generator, the more 240 V loads you can put on it rather than 120 the better because 240 V loads load down both armature windings equally, whereas the same amount of power on a 120 V load takes it all from just one of the two windings. When I'm using a portable generator with a long extension cord and a tool that draws a lot of current, I run 240 volts through the cord and have a 240/120 step-down transformer I put at the end of the cord to plug the tool into. This is not only easier on the generator but cuts my line losses by half so the tool gets more voltage. The transformer is in a sturdy case and has a handle on top for easy carrying.
Bottom line is if your military unit is the Onan 5/6.5 kW one, it's definitely a step above the "emergency backup" grade of portable generators and is made to run for a long time. They run at 1800 rpm rather than 3600 like the "emergency" ones. They have an oil pressure shutdown switch that cuts off the fuel solenoid, and glow plugs in the air intake for cold starting. It takes a good beefy battery to crank them enthusiastically, so make sure your battery is good. Not sure if the military version has a 12 or 24 volt starter. Fuel economy is good. Noise is not too bad with a car muffler on it. Weight is about 700 lbs so it's not something you want to pick up and move around a lot. With any genset, long periods of running at full speed with no load are hard on an engine. Better to pick a genset that's small enough that you'll be putting full load on it occasionally than one that's "loafing" all the time. Maybe that means you can't turn on absolutely everything in the house all at once, but that's okay.