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Operating Instructions
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4.0 OPERATING INSTRUCTIONS
Refer to Figure 5.
4.1 Initial System Start-Up
All load circuit breakers and tie circuit breakers are initially open.
1. Press the CLOSE LOAD 1 button located on the panel behind the Control door. The Load 1
breaker should close when the button is pressed.
2. Press the CLOSE LOAD 2 button located behind the Control door. The Load 2 breaker should
close when the button is pushed.
3. Once one or both UPS systems are on-line, a transfer of either critical load between systems or a
continuous tie operation can be performed subject to conditions outlined in 1.0 - System
Description and 2.0 - Operation Description and the following sections.
4.2 Basic Operation
4.2.1 Momentary Tie - Load Transfers
A momentary tie operation is used to transfer a critical load from a UPS system, which requires isola-
tion for maintenance, to another UPS system without placing the critical load on utility bypass.
The isolated UPS system can be serviced while the critical load remains protected by a fully func-
tional UPS system. Once service is complete, perform another Momentary tie operation to return the
critical load to its normal UPS system. This can be done without placing the critical load on utility
bypass.
4.2.2 Normal Transfer Operation Configurations
Transfers of a critical load between systems can be performed from several initial system configura-
tions. The guiding criteria for permitting transfers is that the critical load must remain on UPS
inverter output.
Transfers to a UPS system operating on its bypass source cannot be initiated due to logic lockouts.
However, a critical load initially on a UPS system’s bypass source can be transferred to the other UPS
system operating on inverter output.
In addition to checking system configurations, the Power-Tie logic uses three independent criteria for
verifying synchronization. The Power-Tie logic verifies system voltages are within proper limits. And
the Power-Tie logic verifies the UPS system which will accept the additional load has sufficient UPS
capacity.
The logic intelligently determines which system to synchronize with, which UPS system capacity to
check, and which load(s) to check, based on which system the operator selects to transfer load. The
Power-Tie logic “knows” the present system configuration.
The Power-Tie logic automatically returns both UPS systems to independent operation by resynchro-
nizing them to their own bypass source and separating all control loops between the systems when
the transfer is complete.
4.2.3 Maintenance Procedures - Isolating Each UPS System
Power-Tie system capabilities permit each UPS system to be completely isolated for service while its
load continues to be powered and protected by the other UPS system. In addition, since all controls of
each system are electrically isolated from the other system, any operation or fault on the system being
serviced does not affect the system supplying the combined loads.
NOTE
The operation can be performed with the UPS on bypass or inverter output. The Power-Tie
logic confirms that the Tie breaker is open to prevent inadvertently putting the systems in
parallel.