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SYS-APM001-EN Chiller System Design and Control 95
Failure Recovery
With all the varied approaches available to potential customers, it sometimes
seems that the main idea gets lost. People purchase chilled-water plants to
reliably produce chilled water to satisfy another need, such as comfort or
process cooling. Therefore, when the plant operates there must be a process
in place to recover from the failure of a chilled- or condenser-water pump,
cooling tower, or chiller. Failure recovery should be integral to the chilled-
water plant control system. Refer to Figure 57. If the control sequence tries to
start Chiller 2 and its pump, but the pump has an electrical malfunction, the
sequence should immediately lock out Chiller 2 and its pump. The control
system should then automatically attempt to start Chiller 3 and its pump. At
the same time, the control system should send a pump malfunction alarm to
the system operator.
Figure 57. Failure recovery
Chiller 3 Start
Chiller 2 Unavailable
Chiller 1 Running
Bypass Line
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