June 1, 2000

TT #9 BOA Paxinos #2 Onan Generators

By: Rob Lowe

Technical Tips #9 


 Notes And Updates: Modern RV's are equipped with elecrtrical systems that automatically control the generator output and the informartion contained in this article while relevant for older RV's it is no longer accurate for newer RV's. In many of these coaches, both output circuits are wired in parallel supplying increased wattage availalbe to all circuits.

Paxinos Technical Seminar Overview (#2)

After attending the Fall BOA Rally in Paxinos, many of us learned some additional information about our Bounders. In this article I will continue to cover some of the seminars that I attended and present some of the helpful hints and suggestions that I picked up. I hope you find them useful.

Onan Generator Seminar: Most Bounders are equipped with Onan generators the seminar conducted by Mr. Bill Murphy of Onan Corporation was quite informative. He noted that the Marquis 5000-watt generator (black in colour) has been re-rated to 5500 watts in 1998 with no changes to the unit. It appears that in performance tests of this generator model on the assembly line it has been consistently producing 5,600 to 5,800 watts and its durability has been exceeding earlier models. Thus, if you have a Marquis 5000, you have actually have a 5500-watt unit. It is critical to regularly check the oil level since most Onan generators are designed to burn a certain amount of oil. Onan owners' manuals are being rewritten to remove references to 30-weight oil, since all of their generators will perform better with multigrade oil typically 15W40. He highly recommended switching to this grade at the next oil change. Oil and oil filter should be changed every 50 hours of operation, or once per season regardless of the amount of use. Onan filters are recommended primarily because they include check valves in the system that other after-market filters may not. Using other brands of filters may prevent proper oil flow through the engine causing severe mechanical failure.

Bill said that the most common problem that he sees as he travels throughout North America is under use of the generator. He used the term "use it or lose it" to describe the performance of their units, noting that more fail from lack-of-use than over-use. The recommended monthly exercising is to run the generator for a minimum of two (2) hours under half to three quarters load (both air conditioners and an electric heater running) to remove the condensation of water that naturally occurs in RV generators. The use of the generator to power the air conditioners as you travel rather than engine driven air conditioners is also recommended. Not only is it more fuel efficient, the generator also gets the use it needs to perform longer.

Remember that the usual design of the generator and Bounder electrical system is that one 30 Amp circuit breaker on the generator supplies power to the coach and one air conditioner (typically the front). I call this breaker the main or primary breaker. The other 20 or 30 Amp circuit breaker on the generator supplies power strictly to the other air conditioner (typically the rear). Which air conditioner is connected to the main circuit breaker on the generator is determined by the "front - rear" air conditioner selector switch in your coach's electrical circuit breaker compartment on the older bounders or by the Electronic control system on the newer coaches. If the selector switch is set to front (implying that when you are in a campground the front air conditioner will receive campground power) then the rear air conditioner is the "other". If it is set to the rear, then the front air conditioner is connected the other generator circuit. Using one air conditioner (which consumes about 1,500 to 2,000 watts) does not fully load the generator and using an electric heater conditioner (which consumes about 1,000 to 1,500 watts) only loads the main generator circuit. The other circuit has no load and the generator is running at about half its capacity. Proper exercising of the generator requires both circuits to be loaded and thus you must use both air conditioners. If your coach has only one air conditioner then the generator utilizes only one circuit breaker even though it has two power circuits.

This seminar together with the plant tour also demonstrated that more Bounders are being equipped with smaller capacity generators. Cost saving is one reason, another is more efficient appliances and air conditioners combined with better designed generators that can run for extended periods of time at higher load levels. The winner is the Bounder owner since the generator is operating at more efficient power levels.


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