Of Course I Have a Backup Generator

By Richard P. Bingham | Dec 15, 2005
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At a recent National Electrical Code taskforce meeting dealing with mission-critical facilities relative to scenarios proposed by the Department of Homeland Security, the main concern seemed to be “you can’t test critical facilities. I want to make sure they work when I need them, but testing might cause damage.”

The person who related the story said that he had heard this same complaint when visiting facilities to check their operational readiness. This wasn’t just one person’s experience, either. Others echoed it in the group as well.

Just like any piece of equipment, backup generators used in emergency power systems need a preventative and routine maintenance program. Contrary to the above concern, not periodically running the generator increases the odds of system failure.

It is just like your car or truck—leave it in the garage for a couple of years without using it and the battery will probably be dead. However, if you ran it every day, you’d be confident that it would work each time you turned the key. In fact, the battery is the most common problem diesel generator suppliers encounter with generators that fail to start.

There are several excellent resources for developing a maintenance program for backup generator systems. One of the best is the NFPA 110 Standard for Emergency and Standby Power Systems.

Another more general source, but with a specific section on generator maintenance, is the NFPA 70B Recommended Practice for Electrical Equipment Maintenance. Most of the manufacturers of such equipment have valuable information on the subject, such as the Cummins Power Generation Web site,

Some maintenance tasks should be conducted weekly. Others are monthly, quarterly or yearly. The frequency depends how important the facility thinks testing is to ensure the generator will function if utility power isn’t adequate (or when someone presses the “test” button). The basic concept is similar to checking out your vehicle before going on a long trip—you’d give all the vital organs (fuel, oil, coolant, tires, etc.) a once-over just in case.

Depending on the length of expected run-time, there might be a main supply and day tank for fuel storage. If the fuel is too old, it could contain condensation.

The oil needs to be changed annually or after 50 hours of operation—whichever comes first. Make sure the coolant system is clear of air obstructions on the louvers, heat exchanger and radiator and has proper antifreeze -protection.

The water jacket, hoses and pumps should be leak-free. Don’t forget to check the electrolyte level and specific gravity. When operating, the charger should fully recharge the battery, just like in your vehicle.

Electrical wiring, switches and lights should be inspected, and circuit breakers, fuses and transfer switches cleaned annually. Just like a vehicle engine, the prime mover’s ignition and fuel components need routine maintenance.

Don’t forget the heart of the system—the generator; it should be have a physical inspection, cleaning, electrical tests and even occasional impedance tests.

With the visual inspections, checking, component changes and cleaning completed, it is time for weekly or monthly operation tests. The actual run-time and test frequency is based on the classification of the emergency power supply system. This determines whether failure of the equipment to perform could result in the loss of human life or serious injury, such as with hospitals and emergency response call centers.

“It is important that a program be in effect to ensure that the generating unit will be test-run on a regular basis and also be subjected to a full-load test at least monthly for a minimum of 2 hours,” states the NFPA 70B 2002 Section 25.3.5. “In addition, generator startup, transfer, restoration of power, retransfer, and auxiliary generator shutdown operation should be checked at least twice a year.”

Running the test for 30 seconds is just as bad as not running the test at all. Enough time must be allotted to recharge the batteries and drive the moisture out of the system.

If the load in the facility changes, test the generator to see that it will adequately carry the load, and not just on a kilovolt or watt rating. Many of the electronic loads found in today’s facilities result in significant harmonic currents. Generators can be victims of harmonic currents, just like motors and other electromagnetic equipment. Harmonics can result in overheating, especially where higher order harmonics are present.

To all of those people out there who are afraid to press the button: Develop and carry out a preventative maintenance program on your emergency power system. You too will be able have the confidence that it will work as required, when required—whether for a real emergency or routine test. EC

BINGHAM, a contributing editor for power quality, can be reached at 732.287.3680.


About The Author

BINGHAM, a contributing editor for power quality, can be reached at 908.499.5321.





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