Originally Posted by bapos
Do you have a generator preference? I am not in love with any brand (I am partial to Honda products but they dont make many models for rvs) so I am wide open to suggestion? . . .
There is no answer right for everyone. I don't want to start a food fight, like the Ford vs. Chevy vs. Chrysler opinions of the 1960's. What is right for a couple camping 2-3 weekends a year, and what is right for a family of 5 living in their bus full-time would probably be totally different.
The correct answer for each user is a balance (or compromise) of:
- Cost of acquisition (free is good, if it works)
- Cost of operation and maintenance (fuel, routine service, breakdown repairs, overhauls)
- Reliability - "mean time between failures"
- Life expectancy (could be measured in years or operating hours)
- Frequency of use
- Type of fuel
- Rated capacity versus expected loads
(Note that the "full time" or "primary power" rating of most gennys is about 2/3 to 3/4 the short-term "standby" rating that is typically published. Try to stay within the "full time" rating when sizing the genny and loads. If in doubt, select the next size larger.)
The generators I oversee are stationary powerplants to back up communications - about 2 dozen 8.5 kW Kohlers, some Onans ranging from antique 3 to 5 kW models up to new ones rated between 65 or 70 kW, plus a couple of other oddball makes thrown in. I assist with but am not responsible for the maintenance on mobile and portable genny units.
The first thing I would say, is that I would prefer any generator that runs at 1800 RPM over a similar generator that runs at 3600 RPM.
Except for the small inverter generators that use electronics to generate 60 Hz, the frequency of the AC must be maintained by the engine RPM. A unit that turns half as fast is likely to last more than twice as long. The slow units are most likely to be diesel powered.
Then there is the question of fuel. One consideration is matching the engine fuel supply and plumbing a permanently-mounted generator into the same tank(s), so that you cut down on the types of fuel you carry and handle. Other considerations:
Diesel engines are harder to start cold. Diesel engines have more torque. Diesel fuel can absorb water and grow bacteria if it sits.
Gasoline is readily available, at least for now. Gasoline goes bad fairly rapidly, and will gum up your carburetor, perhaps permanently, if it is not used often. A generator used once per year is asking for trouble, one used every week and refueled should never have a problem.
Liquified Propane never goes bad, but is under pressure and will disappear if you have a leak. Propane can give you quick starts if you can flow enough vapor. The tank(s) need enough surface area to boil off vapor from the "superheated" liquid during a heavy draw. Three 20-lb barbecue tanks in parallel will flow three times more vapor from the combined 60 lbs of liquid than a single 100-lb upright cylinder of the same diameter. There's a reason that big LP tanks lie on their side - more vapor-producing area.
Another trick to overcome flow restrictions is to have two regulators - the regulator at the tank would have a higher pressure than the second regulator at the carburetor. The pressure in the tank (when not drawing vapor) can be 90 to 200 psi, depending on ambient temperature. This pressure prevents any more propane liquid from boiling into vapor until a valve is opened. Operating pressure is measured in water column inches, and is generally less than 2 psi. One suggestion would be a 14-inch pressure regulator at the tank feeding into the fuel lines, followed by the standard (7-inch?) pressure regulator at the generator, not at the tank.
Propane tanks must draw heat from the air to boil some more of the liquid when the existing vapor starts to be drawn off. I have heard of tanks mounted in closed RV compartments in winter drawing enough heat to cause chilling of the water vapor in the surrounding air into ice, freezing the regulator into cutting off the propane vapor flow.
The third thing I would say, is that I like quiet. I don't like to hear fans, blowers, generators, or loud exhausts. So in general for generators, my preference is the quieter, the better.
The fourth consideration is that liquid cooling for a fixed genny would be preferred for evenness of temperature, but the weight savings of air cooling makes a portable generator portable.
Finally, many people have taken generators meant to be portable, and have adapted them to mount semi-permanently in vehicles.
So, my preferences. If I was contracted to equip a tour bus for the Rolling Stones, money no object, but it had better work every time, I would probably pick a liquid-cooled Onan Quiet Diesel. We have had good luck with the three we have, and they are not too obnoxious noise-wise in their special cabinets. But they are "spendy."
For small generators, the attitude is either buy cheap, and toss it if it breaks and can't be fixed, or buy quality and make it last. Some people like their Hondas, some are happier buying half-price knock-offs.
I am in both schools. Even though I hate noise, I am tempted to get one of the Harbor Freight 2-strokes that put out 600 watts for $90 with magazine coupon, just to have a tiny unit to toss around for projects or emergency back up to a primary one.
Next size up, I am leaning toward the pricier Yamaha inverter units over the similar Hondas. They are rated a few db quieter, and most models have cast iron cylinder sleeves for better wear. I am leaning toward a portable unit of about 2 kW pre-converted for "tri-fuel" including propane from the link I posted earlier. This would be for battery charging and light duty, not for running air conditioners. I am of the minimalist, off-grid mentality, and hopefully the genny would be used to back up a solar charger on cloudy days, and not be used to run everything for 16 waking hours per day.
Anything larger would be whatever I could get a killer deal on, whether rebuilding a scrapped unit, or someone getting rid of a used unit at an overly reasonable price. If I were to run air conditioning, I would look at the used market and compare price to condition on available 4 to 12 kW units, and select the most promising compromise.