Frequently Asked Questions
Do you have a question about a Cummins Onan Commercial product? Browse through our Frequently Asked Questions below -- you may find that we already have an answer for you. We will be adding new questions regularly, so please check this page often.
If your question isn't addressed here, please contact your local Cummins Onan Certified Dealer/Distributor for assistance. They are your source for Cummins Onan parts and accessories, manuals, technical advice, maintenance service and repairs. Or if you already own a Cummins Onan Commercial generator you can download or view your operators manual online.
What is the difference between a generator that utilizes brushes and one that does not, and which should I choose?
Cummins Onan generators use electrographic brushes that typically have a wear out interval of 2000+ hours. Given this relatively long service interval, there is no technical advantage to a brush vs. non-brush system. This should not be a major concern when selecting generator sets.
Brush type alternators do have an additional service point. Replacing brushes is much less expensive that replacing a brushless exciter system should it fail.
Do diesel generators need exercising like gasoline generators?
Yes, regular exercise helps lubricate the seals and engine components and keeps carbon from building up. Regular exercise also heats up the generator windings and removes or expels excess moisture. In sets equipped with brushes, exercising helps prevent corrosion build up on the slip rings.
How often should I run my gasoline generator to keep it in good condition.
It may seem strange that not using a machine could cause performance problems, but with commercial vehicle generators that's exactly the case. Regular "exercise" is an important part of keeping your generator healthy. Lack of use can cause moisture build-up and fuel system damage that make it run poorly. In fact, in as little as 30 days, the fuel in gasoline-powered generators can begin to break down into gums and varnishes that clog the fuel system. Fuel varnishing results in hard starting and surging. (A surging generator never settles at a stable operating speed.)
To prevent such problems, we recommend running gasoline generators at a minimum of 50 percent capacity for two hours at least once every four weeks. A long two-hour exercise period is preferable to several short periods.
Is generator power clean enough to run a computer?
Yes, with Cummins Onan generators this is no problem. The generator set should be turned on and warmed up before turning on the computer. The normal precautions for home use should be followed for RV use as well.
What is the single biggest issue with a generator set installation?
Making sure cool air gets to the generator set and warm air gets out of the generator set, without mixing or recirculating. If in doubt about the correct installation process, we recommend that you have the work done by a certified dealer or distributor of Cummins Onan commercial vehicle generators.
Are there Cummins Onan hydraulic generator sets? What is the warranty?
Yes. The Cummins Onan hydraulic generator models, offered in 6-25 kW, are manufactured to the highest standards and are designed to provide, clean, quiet power; single-side serviceability; flexible installation and high motor-starting capability.
The HG Series is an engineered hydraulic generator system including the hydraulic pump, motor, generator, filtration system, oil cooler and reservoir in one complete, compact, and lightweight unit.
The Cummins Onan limited warranty covers virtually everything except routine maintenance for the first five years that you own your generator set, or the first 1,000 hours of operation, whichever comes first. In addition, it includes a free 90-day adjustment policy, which provides that Cummins Inc. will make minor adjustments to your new generator set during the first three months you own it -- free of charge!
Travel Time Repair Allowance: In addition to the 5-year, 1000-hour warranty, travel time repair allowance of 2.5 hours and mileage cost up to 100 miles is included for the first 2 years.
Do you have any accessories for these generator sets?
Yes, accessories such as tail pipes, remote panels & harnesses, muffler kits, etc., are available through your local Cummins Onan dealer/distributor. If there is an item not carried by your local source, you can contact Onan Indiana by phone at 1-800-589-9027 or online at www.onanindiana.com.
What are the advantages or disadvantages of a piston pump motor or a gear pump motor?
The Cummins Onan HG Series 20 & 25 kW uses a piston pump motor to drive the alternator because a piston pump motor is required in a closed loop system. Closed loop systems are much more efficient in the higher kW ranges.
On the 6-15 kW we use an open loop hydraulic system. The axial piston pump does not offer a substantial technical advantage over the gear pump. In this application the gear pump could theoretically wear out a little faster. In this application the expected life of the gear pump is pretty close to the expected life of the axial piston pump.
Dirt is the major failure mode culprit in almost all hydraulic system failures. Should a piston drive motor be damaged from dirt contamination, it will be more expensive to replace than a gear pump. The gear pumps are also more forgiving with contamination.
Can I rewire my Cummins Onan generator from 120V to 120V / 240V?
No, on the newer generators you generally cannot.
