Daikin WGZ030DW Installation, Operation And Maintenance Manual page 42

Evaporator Water Pump State Control (Evap State)
The state-transition diagram shown below controls operation of
the evaporator pump.
Figure 22: Evaporator Pump State Diagram
Pump Selection
The pump output used will be determined by the Evap
Pump Control set point. The setting allows the following
configurations:
#1 only – Pump 1 will always be used .
#2 only – Pump 2 will always be used .
Auto – The primary pump is the one with the least run hours,
the other is used as a backup.
#1 Primary – Pump 1 is used normally, with pump 2 as a
backup .
#2 Primary – Pump 2 is used normally, with pump 1 as a
backup .
Primary/Standby Pump Staging
The pump designated as primary will start first. If the
evaporator state is start for a time greater than the recirculate
timeout set point and there is no flow, then the primary
pump will shut off and the standby pump will start. When the
evaporator is in the run state, if flow is lost for more than half
of the flow proof set point value, the primary pump will shut
off and the standby pump will start. Once the standby pump
is started, the flow loss alarm logic will apply if flow cannot be
established in the evaporator start state, or if the flow is lost in
the evaporator run state.
Auto Control
If auto pump control is selected, the primary/standby logic
above is till used. When the evaporator is not in the run state,
the run hours of the pumps will be compared. The pump with
the least hours will be designated as the primary at this time.
IOM 1322-1 • WATER-COOLED SCROLL COMPRESSOR
Evaporator Water Flow Loss
The Evaporator Water Flow Loss logic allows the Unit to
shutdown compressors on a loss of flow up to two times every
twenty-four hours before locking the unit out on a Evaporator
Flow Loss Alarm.
• If there are no compressors running when Evaporator
Water Flow Loss is indicated the Unit Status changes
to Auto: Wait for flow. The evaporator water pump state
changes to Start and no alarms are indicated.
• If an Evaporator Water Flow Loss occurs while a
compressor is running all of the running compressors will
be shutdown. The alarm indicators are turned On and the
Circuit Status for any circuit with running compressors
becomes Off: Ready, the Unit Status becomes Auto: Wait
For Flow and the evaporator water pump state changes
to Start
• When flow is reestablished the Unit Status becomes Auto:
Recirculate while the Evaporator Flow Recirculation Timer
counts down. If there is continuous evaporator water flow
while the Evaporator Recirculation Timer counts down the
Alarm indicator is turned off, and the unit resumes normal
startup procedures based on water temperature and
cycle timers.
• If second Evaporator Water Flow Loss occurs within
twenty-four hours the process described above is
repeated.
• If a third loss of flow is indicated in a twenty-four hour
time frame the unit will shut down on an Evaporator
Water Flow Loss alarm and it will be locked out until this
alarm is manually cleared.
• The twenty-four hour timer that limits the auto restart is
reset when the control clock rolls over 00:00 each night.
Condenser Pump and Tower
Control – Water Cooled
Condenser pump and cooling tower control logic requires that
the unit be configured as water-cooled in order to be active.
Condenser Water Pump State Control
(Cond State)
If the unit is configured as water-cooled, then the state-
transition diagram shown below defines the condenser pump
control logic.
42
Unit Controller
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