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performed, current is drawn from the batteries. This action results in the unit annunciating that the
batteries are being discharged. At the unit, this is accompanied by the yellow “BATTERY
DISCHARGING” light turning on and an audible alarm sounding. Remote annunciation panels will also
indicate that the battery is discharging.
One other parameter that needs to be set is the percent charge level that is used to indicate a capacity
test failure. This value should normally be set at 60%; however, if your batteries are older and starting
to fail at this level, but 60% is still able to get you the backup time you need, you may want to reduce
this level to a lower value. This way you know that you will need new batteries soon so you can begin to
budget for such an expense. In the mean time, you can continue to operate without receiving a
continuous warning message. Should the batteries degrade further, the lower level will begin to be
exceeded, telling you that you might want to step up the timeframe for replacing the batteries.
Capacity tests can not be performed unless a Quick test is performed first, as it is necessary to check
the integrity of the battery prior to checking its capacity. Therefore, it is not possible to perform
automatic Capacity tests more often than automatic Quick tests; however, it is possible to perform
Quick tests without performing a Capacity test. If daily Quick tests are performed, such tests will be
performed each day during the hour indicated on the automatic battery test setup LCD display. If the
unit can not perform a test anytime during that hour because the batteries are not charged sufficiently
due to a recent power failure, no AC line present during that hour, or the unit being off, no test will
occur again until the following day during that hour. Quick tests and/or Capacity tests performed on a
weekly basis will only be performed on the programmed weekday during the programmed hour. If
unable to perform the test at that time, the UPS will attempt again the following week. Quick tests
and/or Capacity tests performed less than weekly will only be performed on the programmed weekday
during the programmed hour if the prescribed number of weeks have passed since the last test. If
unable to perform the test at that time, the UPS will attempt again the following week. If a test is started
but can not be completed due to an AC line or other problem, the test will not be repeated until the next
programmed interval has passed.
Manual battery tests actually consist of a Quick test followed by a Capacity test. Manual tests will not
result in a failed capacity result unless the charge percentage drops below 20% (not programmable).
However, manual battery tests may be terminated early by the operator.
8.5 OTHER PREVENTIVE MAINTENANCE
The Mesta UPS has been designed for long, fault-free operation. However, to detect possible
developing problems, it is advisable to perform the following list of preventive maintenance on a
monthly or other regular basis interval. The parameter monitoring can be performed using either the
front panel keypad and LCD display, or using a computer/terminal connected to the serial port of the
UPS.
Check all input and output voltages and currents. Make sure voltages are close to the nominal
values and are not approaching either the minimum or maximum levels that can be tolerated by
the UPS. If input voltages are too low or too high, it may be necessary to change a tap on the
distribution transformer feeding the UPS. Check the %RATED output currents to insure that no
phase is pulling more than 85 to 90%. Consider redistributing single phase loads so as to better
balance the load currents, or dropping less critical loads from the UPS if at or above this level. The
UPS will have no problem operating at up to 100% loading; however, any fluctuations in the line or
load could cause the output current to exceed 100%, which could result in an overload shutdown.
You, therefore, want to make sure you have at least a 10 – 15% margin to prevent an overload
condition from occurring.
