The Parallel Redundant configuration is the most used UPS configuration in the world. However, it can be shown that the maintenance bypass switch introduces a single point of failure and thereby reduces the overall reliability. A maintenance bypass will be required to allow service and maintenance of the UPS system (so configured) without disconnecting the critical load from a power source. Likewise, a Hot-Tie configuration, which is two separate UPS systems joined by a static transfer switch, has a single point of failure at the switch. Such single points of failure significantly reduce system MTBF.

Regardless of the configuration, the system’s reliability can be dramatically degraded if it is poorly maintained. Since people cause 50% of all UPS system failures, the key to uptime is proper training of the operating personnel. Other key points for preventing such degradation are as follows:

  • Post clear, concise operating instructions
  • Regularly scheduled maintenance by qualified personnel
  • Knowledge of battery’s health and capacity
  • Circuit breaker coordination
  • Spares inventory
  • Test the availability of the backup AC sources
  • Participate in a product upgrade program with the UPS vendor
  • Place the UPS alarm where it must be acknowledged

About PS&C

Power Systems & Controls is a world leader in power quality and power protection technology, building systems for mission critical applications world-wide. Clients include many of the world’s leading research and test laboratories, rail and sea mass transit, advanced manufacturing, and data centers. The company was founded in 1965 by CAT. Today the company is headquartered in Richmond, VA and supports the USG and DOD, Fortune 500, and many other international organizations on a wide range of applications. We don’t just solve power problems; we engineer power solutions.