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Flooded type water cooled screw chiller (PCB Control)
MCAC-CTSM-2012-11
82
Note: In pump mode, it can transfer to cooling mode directly; in cooling mode, it needs to stop the unit
and pumps first, then transfer to pump mode.
When accumulative total running time reaches 3,600,000s, remind user servicing water system and
performing scheduled cleaning work.
Cooler and Condenser Pump Control
Midea chillers can be configured for cooler and condenser pump control. Inputs for a cooler pump
interlock and condenser flow switch or interlock are provided. Refer to appendix for details.
Cooler pump control
Proper configuration of the cooler pump control is required to prevent possible cooler freeze-up. A
cooler flow switch must be installed on the outlet of chilled water to prevent operation without flow
through the cooler. The chiller is also interlocked with the chiller water pump starter to provide
additional protection. See appendix of the Field Wiring section for proper connection of the cooler
pump interlock.
All chiller cooler pump control is utilized unless the chilled water pump runs continuously or the
chilled water system contains a suitable antifreeze solution. It is recommended that the cooler pump
should be interlocked with the unit unless there’re other antifreeze solutions.
When the cooler pump control is “ON,” the cooler pump relay will be energized when the chiller
enters an “ON” mode. The cooler pump relay will remain energized for 10 min after all compressors
stop due to off command in order to prevent freeze-up. In the event a freeze protection alarm is
generated, the cooler pump relay will be energized whether cooler pump control is configured “ON”
or “OFF.” The cooler pump relay is also energized anytime a compressor is started as well as when
certain alarms are generated. The cooler pump relay should be used as an override to the external
pump control if cooler pump control is not utilized.
IMPORTANT:
If the cooler pump control relay output is not wired to control or override the operation
of the chilled water pump. An OFF DELAY of 10 minutes must be provided after the chiller is disabled
to maintain cooler water flow during the pump down period.
If the chilled water flow switch/interlock does not close within 5 minutes after the unit is enabled and
in an “ON” mode when cooler pump control is turned “OFF” or “ON”, water flow loss alarm will be
generated.
No matter water pump is “OFF” or “ON”, if water flow switch opens for 5s continuously, the unit will
not start or stop immediately.
Condenser pump control
The condenser pump can be controlled in the way like the cooler pump. It is turned on whenever the
machine is in an “ON” mode and turned off 60 seconds after all compressors stop. When configured
for a condenser flow switch/interlock, an alarm of cooling water flow loss is generated if the input
does not close after unit starts for 2 min and fault will be displayed on the operation interface.
Flow Sensor
Water flow protection
All water pipe kits and water flow switches are provided. Water flow switch must be installed on the