APC 900XL Power Supply User Manual


 
Page 21
5.0 Operation
Note: Option switches may
be thrown at any time and
take effect immediately.
5.5.3 Replace battery
In the event the UPS's battery fails a battery test, the UPS will emit "chirps" for a period
of 1 minute. If the UPS is left operating while in this condition, the UPS will emits chirps
once every 5 hours until a successful battery test is completed.
5.5.4 Overload
The UPS will emit a loud, sustained tone when overloaded. When an overload is applied
while on-line, the alarm will sound until the overload is removed. If the overload is
applied while on-battery, the alarm will sound until the UPS Enable control is switched
off.
5.6 Option switches
5.6.1 Option switch 1
The UPS contains utility fault detection circuitry that is extremely sensitive to line
voltage distortions including spikes, notches, sudden dips and swells. The UPS is factory
set to react to such line voltage distortions by transferring the load immediately to on-
battery operation. This affords maximum protection for all load types. Where power
quality is poor due to local cyclic heavy load switching or use of inexpensive fuel
generators, the UPS may be caused to transfer to on-battery operation very often. If the
UPS is powering loads that are known to operate normally under such conditions, such
behavior is undesirable as battery capacity is being spent unnecessarily.
The user may set Option switch 1 to the on ( I ) position in order to desensitize the UPS
to rapid low amplitude line voltage fluctuations. When this is done, the UPS's upper
transfer voltage is also increased by 3%, for a total of 13% above the nominal input
voltage. This allows the UPS's battery charger to maintain maximum possible battery
capacity, saving it for gross utility failures.