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Operating Instructions
29
4.2.11 Continuous Tie-Systems
A UPS system that has lost one or more modules can be taken off-line for service. The UPS system
with partial capacity can be continuously tied to the other UPS system (also full or partial capacity)
and the critical loads of both systems are protected by the single, fully redundant UPS. When service
is complete the UPS module(s) can be brought on-line again and the system separated, without plac-
ing a critical load on the Bypass source.
Normal Operating Configuration
Initially both load isolation breakers are closed. The Tie breaker is open. Both UPS systems are on
inverter output. See Figure 5.
Once the Tie operation is initiated the systems synchronize to the selected Primary Bypass source.
The Power-Tie logic checks the system configurations, verifies synchronization, verifies system volt-
ages are within proper limits, and verifies that the on-line UPS modules of both system have suffi-
cient capacity to maintain the combined loads before allowing the systems to be tied.
Tying the UPS Systems - Continuous Parallel Operations
Both load isolation circuit breakers will be initially closed and the Tie circuit breaker initially open.
The Tie circuit breaker is closed if the systems are in a combined loads mode. Both UPS systems will
be on inverter output.
1. Select the Primary Bypass source for the combined systems with the PRIMARY BYPASS
SELECT switch in the CONTINUOUS TIE CONTROL section of the control panel. If System 1
will be the Primary Bypass then the switch should be in the SYS1 position.
2. Press the SYNCHRONIZE SYSTEMS button in the CONTINUOUS TIE CONTROL section of the
control panel. The push button turns on.
3. Wait for the OK TO TIE SYSTEMS light to turn on.
4. After the OK TO TIE SYSTEMS light turns on, press the PUSH TO TIE SYSTEMS AFTER OK
button. The Tie breaker will close to put the systems in parallel operation.
5. Both systems will share both critical load feeders.
Returning Parallel Systems to Normal Operation - End Continuous Tie
Both Load circuit breakers and the Tie circuit breaker will be initially closed.
1. Press the SYNCHRONIZE SYSTEMS button. The light turns off.
2. Wait for the OK TO OPEN TIE light to turn on.
3. Once the OK TO OPEN TIE light turns on, press the PUSH TO OPEN TIE AFTER OK button.
The Tie circuit breaker opens, separating the systems.
4. Both UPS systems will supply their normal load feeders and operate independent of each other.