simultaneously supply the inverter with dc power and recharge the battery.
This shall be an automatic function and shall cause no disturbance to the
critical load.
1.3.4.4
Failure of ac Input Power to Return
Should the ac input power fail to return before the battery voltage reaches
the discharge limit, the UPS system shall disconnect from the critical load
to safeguard the battery.
1.3.4.5
Failure of a Module
**************************************************************************
NOTE: Delete for parallel non-redundant
multi-module UPS systems and single module UPS
systems.
**************************************************************************
In a redundant configuration, failure of one module shall cause that module
to be disconnected from the system critical load bus by its internal
protective devices and its individual output protective device. The
remaining module shall continue to carry the load. Upon restoration of the
failed module, it shall be possible to reconnect the failed module to the
critical load bus to resume redundant operation without disruption of the
critical load.
1.3.4.6
Transfer to Bypass ac Power Source
**************************************************************************
NOTE: Edit as required for parallel non-redundant
multi-module UPS systems or single module UPS
systems.
**************************************************************************
When the static bypass switch senses an overload, two or more inverter
shutdown signals, or degradation of the inverter output, the bypass switch
shall automatically transfer the critical load from the inverter output to
the bypass ac power source without an interruption of power only if the
connected load exceeds the capacity of the remaining on-line modules. If
the bypass ac power source is out of normal tolerance limits, the UPS and
the critical load shall shut down.
1.3.4.7
Retransfer to Inverter
The static bypass switch shall be capable of automatically retransferring
the load back to the inverter output after the inverter output has returned
to normal conditions. Retransfer shall not occur if the two sources are
not synchronized.
1.3.4.8
UPS Module Maintenance
**************************************************************************
NOTE: Delete for parallel non-redundant multi
module UPS systems and single module UPS systems.
**************************************************************************
UPS modules shall be capable of manual disconnection from the critical load
bus for maintenance without disturbing the critical load bus.
SECTION 16265A
Page 11
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