An in-house maintenance program for uninterruptible power supplies (UPS) targets two major components: batteries and the system itself. Each one is critical to the reliability and long-term performance of the UPS. The type of batteries installed, along with their capacity, will dictate the type of maintenance tasks technicians perform and the tasks’ frequency.
For example, smaller passive-standby systems generally use sealed batteries that require little maintenance. Double-conversion systems typically use flooded-cell batteries that require monthly maintenance. But even though they require more maintenance and are more expensive to replace, flooded-cell batteries offer nearly three times longer performance life than sealed batteries.
Typically, flooded-cell batteries are installed in banks and isolated rooms. In terms of their maintenance, technicians should:
• inspect and test the room’s ventilation system at least monthly to ensure proper operation
• inspect batteries for proper electrolyte levels and signs of leaks
• inspect terminals for signs of corrosion and accumulation of dirt, as well as measure and record the voltage and current of the entire bank.
• record the voltage for a random number of individual cells and test their electrolytes
• record measurements in a log to track battery performance.
Twice annually, technicians also should inspect and re-torque the system’s battery connections. Loose connections lead to a buildup of heat at the battery terminals, decreasing system capacity, reducing battery life, and creating potential fire hazards.
They also should load-test the battery bank annually to determine its capacity. This process requires disconnecting the UPS from its power source and allowing the batteries to supply power to a connected load. The test continues until the system design reaches its run time or until the system shuts down because of low battery voltage. Technicians should conduct thermal scans during the test to identify loose or corroded connections.
The UPS itself also requires regular maintenance. Technicians should take the system offline at least annually to inspect its components for signs of corrosion and heat damage. A thermal imaging system can help identify loose connections and components that can overheat.
Finally, technicians should clean dirt and dust from UPS components, particularly if the accumulations are likely to interfere with heat transfer. Technicians also should re-torque power connections according to the manufacturer’s specifications.
— James Piper, P.E., is a national facilities maintenance and engineering consultant based in Bowie, Md.
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