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CAMPSITE POWER – Chapter 6, Synchronous Generators
In chapter five I wrote about the essential functions of inverter generators. One of the benefits of an inverter generator is the ability for the engine to run at lower speed with a light load and still maintain 120 volts at 60 hertz. This of course saves fuel and lowers noise.
There is another class of generator often used by campers. It is known as a synchronous generator. This class of generator drives an alternator directly from the engine crankshaft. In order to produce the standard 120 volts of alternating current at the correct frequency of 60 hertz, the generator engine MUST run at 3,600 revolutions per minute ALL THE TIME.
Synchronous generators are much simpler than inverter generators since they have fewer expensive parts. Thus, they cost a lot less than their inverter cousins for the same or more wattage output. The downside is they are not as fuel-efficient and can make a whole lot more noise than inverter generators.
I know of only one American company left building synchronous generators in the USA, that is Powermate, the company that reopened the bankrupt Coleman-Powermate plant which had unexpectedly closed in 2008. Not all of Powermate’s products are American made – many are built in China, as are the rest of the portable synchronous generators currently available. They generally have smaller, less efficient mufflers and make more noise than their equally sized counterparts.
Several years ago synchronous generators had a reputation of producing “dirty power”. Many people mistakenly repeated that they were not suitable for sensitive electronic devices like a computer. This is not true with modern electronics. The majority of this class of generator has less than 7% harmonic distortion and can safely power any device in a RV.
National Park Service regulations pertaining to audio disturbances states that “motorized equipment or machinery cannot exceed a noise level of 60 decibels measured on the A-weighted scale at 50 feet” (36 CFR 2.12).
This may sound like mumbo-jumbo with the A-weighted scale and decibel stuff. But, there are meters that are relatively inexpensive that can easily measure the sound level. Many individuals as well as Park Rangers and Volunteer Hosts carry these meters. The current crop of 3,000 watt class open frame synchronous generators coming out of China just barely meet this sound level restriction. Prior to this Chinese design, which uses an automotive type muffler, few if any portable synchronous generators met this low of a noise level. You will find that most of these are rated at no more than 67 dba at 7 meters. This rating complies with NPS regulations. Still, the noise from this class of generators can be considerably more annoying to fellow campers than a well shielded, slower running inverter generator. IMHO, they should only be used in generator designated areas when your neighbors are also running a generator.
Most of these generators use a 200 cc engine that is obviously designed from the durable Honda GX-200 engine . Chinese manufacturers avoid comparing their engines to the Honda engines and will deny any design relationship. Obviously claiming to be like a Honda would create all sorts of legal implications. Still, if it walks like a duck, quacks like a duck and swims like a duck then it must be a duck!
Synchronous generators with engines larger than the 200 cc models usually exceed NPS sound limits and are really not suitable for camping unless you are alone in the middle of the desert.
The 200 cc GX-200 clone will produce a reliable 2,800 watts at a 100% duty cycle – even in 100-degree weather. Ratings of 3,000 to 4,000 watts for these engines are not realistic for continuous duty. They do have some performance problems at altitudes over 6,000 feet and like many gasoline engines require re-jetting of the carburetor.
Under most circumstances, they will power a single rooftop RV air conditioner up to 15K BTU. But, to do so you may need to exclude other parasitic loads in the camper such as the converter, electric water heater and electric operation of the refrigerator.
In March of 2005 I started a thread, 3,000W Chinese Gensets Info on the Woodall’s Forum in the Tech Issues area. Amazingly, the thread is still alive and well. It has become one of the longest running; most viewed and commented threads in the Forum’s history. This is just a testament to the interest RV’ers have in these machines. If you decide to visit this thread be prepared for information overload.
Again, based solely on my experience and opinion, the Champion Power Equipment model 46538 is one of the nicest synchronous generators available. It has a remote controlled electric start and stop, allowing you to turn your generator on or off from inside your camper. It features load shedding and over-voltage protection as well as a nice wheel kit for mobility. Champion gensets are difficult to beat when it comes to quality, performance, technical support, warranty service and replacement parts.
You can reduce the noise from any of these generators with a simple enclosure manufactured and sold by SuperGenProducts. The device is called the SuperGenTent. You can find an extensive testing and review of this product on the Woodall’s Forum here.
In summary, synchronous generators are an acceptable source of portable campsite power. But, be prepared to deal with more engine noise, weight, and fuel usage than the inverter models covered in Chapter 5. This chapter concludes the CAMPSITE POWER series. I hope you found at least some of it beneficial.