By Greg Illes
Before you repair or rebuild that Onan built-in generator, and certainly before you purchase another portable generator, there are some relatively new issues to be aware of and consider.
The old Onan 4KW series, and most older portable generators, use a fuel motor (gas/diesel/propane) to drive a motor-generator. This requires that the engine run at a constant 3,600 rpm in order to achieve the standard 60Hz AC voltage frequency (sine wave). The end result of this technology is a lot of weight and noise.
A typical open-frame portable (think contractors, Home Depot, Harbor Freight, etc.) will make enough noise to compete with jet takeoffs at your local international airport. Say goodbye to a peaceful campground if one of these turkeys is within a hundred yards of your campsite.
The standard of the industry, the Onan 4,000 kilowatt series, is much quieter, but still pretty audible across several campsites. But it’s also HEAVY, almost 200 pounds in a typical installation. People love their Onans because they’re built in, draw fuel from the RV tank, have a remote start and are (mostly) trouble-free. Certainly, if your RV has one already and it’s working okay, you’re not likely looking to replace it. But I’ve run into more than a few RV owners who have bought quieter, more fuel-efficient units to run in addition to their Onans.
For any major change in generator resource, new or replacement, the newest technology to be aware of is the inverter-generator. These products have created a sea change in the market, and I’m kinda surprised that Onan has not come up with a competitive offering. (Are we looking at a replay of the U.S. auto market with Japan?)
The inverter-generator also uses a fuel engine, and many are very quiet in operation. But more importantly, the engine drives a very different kind of electrical generator. This design drives a variable-frequency motor generator which powers a full-electronic inverter power supply. The electronic supply puts out 60Hz regardless of engine speed. Without going into a lot of technical detail, let me just say that the final result is that the engine only has to turn fast enough to power the existing load.
How does this work? If all you’re doing is running your lights and the TV, the inverter-generator runs just above idle, barely audible inside the RV. Fire up the AC or the microwave, and the generator leaps to life, powering up into the typical high-rpm growl (although still MUCH quieter than the open-frame models). When the microwave shuts off, the inverter-generator settles back down to a purr again.
Using one of these in a campground environment is a dream come true. At low load, these little units can’t be heard over a light breeze even in the next campsite. They barely sip gasoline, running many hours on one gallon. There are also remote-start units available, and power ratings from one to four KW and more. The 2KW units weigh about 50 pounds — that’s it.
The next time you see a fellow camper walking around his campsite and it sounds like he’s pumping up an air mattress, go check out his generator. He’s likely peacefully powering his rig with a red (Honda) or blue (Yamaha) inverter-generator, and you can thank him for his campground courtesy.
Editor: Browse through the large selection of inverter-generators available at Amazon.
Greg Illes is a retired systems engineer who loves thinking up RV upgrades and modifications. When he’s not working on his motorhome, he’s traveling in it. You can follow his blog at www.divver-city.com/blog.
