IOM 1322 • WATER-COOLED SCROLL COMPRESSOR 66 www.DaikinApplied.com
The pump designated as primary will start rst. If the
condenser state is start for a time greater than the re-circulate
timeout set point and there is no ow, then the primary
pump will shut o and the standby pump will start. When the
condenser is in the run state, if ow is lost for more than half
of the ow proof set point value, the primary pump will shut
o and the standby pump will start. Once the standby pump
is started, the ow loss alarm logic will apply if ow cannot be
established in the condenser start state, or if the ow is lost in
the condenser run state.
Auto Control
If auto pump control is selected, the primary/standby logic
above is till used. When the condenser 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
The Condenser Water Flow Loss logic allows the Unit to
shutdown compressors on a loss of ow up to two times every
twenty-four hours before locking the unit out on a Condenser
Flow Loss Alarm.
• If there are no compressors running when Condenser
Water Flow Loss is indicated the Unit Status changes
to Auto:Wait for ow. The condenser water pump state
changes to Start and no alarms areindicated.
• If a Condenser 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 O: Ready, the Unit Status becomes Auto: Wait
For Flow and the condenser water pump state changes
to Start
• When ow is reestablished the Unit Status becomes Auto:
Recirculate while the Condenser Flow Recirculation Timer
counts down. If there is continuous evaporator water ow
while the Condenser Recirculation Timer counts down the
Alarm indicator is turned o, and the Unit resumes normal
start up procedures based on water temperature and
cycle timers.
• If second Condenser Water Flow Loss occurs within
twenty-four hours the process described above is
repeated.
• If a third loss of ow is indicated in twenty-four hour time
frame the Unit will shut down on an Condenser 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.
Tower fan control is active when the unit is set up as
water cooled (WaterCooled=On), Tower Control is set to
Temperature, and the condenser pump is in the RUN state.
Staging is based on Entering Condenser Water Temperature
(ECWT). Operation depends on the following parameters.
Condenser pump state
ECWT
Stage up and stage down timer values
Tower set points (Tower Control, Tower Stages, Stage Up
Time, Stage Down Time, Stage Dierential
,Stage #1 ON, Stage #2 ON, Stage Down @, Stage Up @)
When the condenser pump starts, the stage up timer shall
start. The rst stage shall turn ON when the following
conditions are met:
The stage up timer completes
The ECWT is > Stage #1 ON set point
Bypass valve position is > the Stage Up @ set point (only if
Valve/VFD Control set point = Valve Stage
Additional stages can turn on (up to the number specied by
the Tower Stages set point) when above conditions are met for
the next stage plus the following condition:
VFD Speed is > the Stage Up @ set point (only if Valve/VFD
Control set point = VFD Stage OR Valve
SP/VFD Stage)
Down staging shall occur when the following conditions are
met:
The stage down timer completes
The ECWT is < Stage #X ON (Temp) set point – Stage
Dierential (Temp) set point
Bypass valve position is < the Stage Down @ set point (only if
Valve/VFD Control set point = Valve Stage)
VFD Speed is < the Stage Down @ set point (only if Valve/VFD
Control set point = VFD Stage OR
Valve SP/VFD Stage)
Each stage up or stage down event will restart both the
stage up and stage down timers. Only one fan output will be
switched at a time (except that all outputs switch OFF when the
condenser pump state equals OFF).
When the Valve/VFD Control set point is set to None OR
VFD Stage, this output will be set to 0. Otherwise, it shall be
controlled as described below.
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