OMM 1130 43
Pump Selection
The pump output used will be determined by the Cond 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 condenser state is start for a time greater than the
re-circulate timeout set point and there is no flow, then the primary pump will shut off and the standby
pump will start. When the condenser 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 condenser start state, or if
the flow 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
Condenser Water Flow Loss
The Condenser 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 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 flow. The condenser water pump state changes to Start and no alarms are
indicated.
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 Off: Ready, the Unit Status becomes Auto: Wait For Flow and the
condenser water pump state changes to Start
When flow is reestablished the Unit Status becomes Auto: Recirculate while the Condenser Flow
Recirculation Timer counts down. If there is continuous evaporator water flow while the Condenser
Recirculation Timer counts down the Alarm indicator is turned off, 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 flow 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 Fans
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 Differential
,Stage #1 ON, Stage #2 ON, Stage Down @, Stage Up @)
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