Testing, Proper PM Program Essential to Power System Reliability

By Greg Livengood  
OTHER PARTS OF THIS ARTICLEPt. 1: Backup UPS System Maintenance MattersPt. 2: This PagePt. 3: Consider Emergency Response Factors in Backup Power Systems Issues

The first step to having a reliable power system is proper factory testing of the equipment, followed by acceptance testing and commissioning of the complete system on site. Once installed, it is then critical that managers develop a comprehensive preventive maintenance (PM) program and that technicians follow it. Managers can use the following criteria to develop the program:

These references give managers detailed recommended and required PM tasks that are too numerous to list. Also, maintenance and testing requirements vary depending on facility type and the critical nature of the supported loads.

PM Program Components

A typical PM program for standby power systems and equipment can include the following steps:


  • Check the coolant heater, coolant level, oil level, and charge-air piping.
  • Visually inspect exterior of equipment for obvious damage or leaks.
  • Check gauges and instruments.


  • Load test generators and transfer switch operation. For hospitals, the testing frequency must be 12 times per year with intervals of not less than 20 days and not more than 40 days as required by the Joint Commission.
  • Visually examine fuel samples.
  • Check coolant concentration.
  • Visually examine belt tension.
  • Check air filters and battery chargers.
  • Drain fuel filter and drain water from fuel tank. Fix if this is a recurring issue.
  • Drain exhaust concentrate.
  • Check battery electrolyte levels.
  • Check connections for corrosion.


  • Visually inspect for loose connections, burned insulation and signs of wear.
  • Visually inspect fuses for discoloration caused by heat from poor contact or corrosion.
  • For hospitals, perform tests of stored emergency-power-supply systems.


  • Clean crankcase breathers.
  • Check radiator hoses.
  • Visually check for liquid contamination from batteries and capacitors.
  • Clean equipment enclosure.
  • Inspect environment HVAC equipment and performance to check temperature and humidity.
  • Conduct thermal scans of electrical connections to ensure all are tight and not generating heat, which is the first and sometimes only indication of a problem. Using this non-evasive diagnostic tool helps identify hot spots not visible to the human eye. Re-torque if the thermal scan provides evidence of a loose connection.
  • Test entire transfer switching sequence.
  • Exercise main and feeder circuit breakers over 600 volts (V).


  • Provide a complete operational test of the system, including a monitored battery rundown test to determine if battery strings or cells are nearing the ends of their useful lives.
  • Flush and refill the cooling system.
  • Change the oil and filter, as well as the coolant filter
  • Change the air and fuel filters.
  • Inspect the main and feeder circuit breakers less than or equal to 600V, and periodically exercise the components per manufacturer recommendations and test them under simulated overload trip conditions.
  • Test the UPS transfer switch, circuit breakers and maintenance bypasses.


  • Test the main and feeder circuit breakers greater than 600V under load conditions.

Every three years

  • Run a four-hour generator load test.

As needed

  • Test components suspected of being defective or that have been subjected to unusual adverse conditions.
  • Only qualified personnel who have been adequately trained and adhere to requirements of the NFPA 70E, Electrical Safety in the Workplace, and other applicable safety requirements should perform PM work.

Continue Reading: Power Management

Backup UPS System Maintenance Matters

Testing, Proper PM Program Essential to Power System Reliability

Consider Emergency Response Factors in Backup Power Systems Issues

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  posted on 4/19/2013   Article Use Policy

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