Unit installation

OMRCPMICRO 39
Pumpdown
As the system chilled water requirements diminish, the compressors will be unloaded. As the system load
continues to drop, the liquid line solenoid valves will be de-energized and the refrigerant circuits will go
through a PumpDown sequence. As the evaporator pressure falls below the LPCutOut Set Point while
pumping down, the compressors and condenser fans will stop. In the event the evaporator pressure rises
above the LPCutIn Set Point while the refrigerant circuit is in a pumped down mode, the controller will initiate
another pumpdown sequence. The controller will allow a maximum of one pumpdown sequence every two
hours during this operating mode. Refer to the Pumpdown Control section in this manual for additional details.
The chilled water pump output relay will remain energized any time the chiller is in an Off mode initiated by the
system switch, remote switch, pumpdown switches or network communications. When the chiller shifts from a
Cooling/Heating mode to one of these Off modes, the chilled water pump output will remain energized for 60
seconds. This will maintain water flow through the evaporator during pumpdown and prevent rapid cycling of
the chilled water pump.
Start-Up and Shutdown
Prestart checkout
Configuration set points are entered at the factory to set up the software for the type of unit to be controlled.
Typical configuration set points will include (see Menu 23):
Ø Number of condenser fan stages (air cooled units only)
Ø Number of compressors (2 or 4)
Ø Number of stages of capacity (4, 6 or 8)
Ø Air or water cooled
Ø Unit operation (chiller or chiller/Templifier)
Setting of the hex address switches
Figure 12, Hex address switches
The Controller Hex Address Switches for each unit
determine its logical location in a MicroTech network.
If the chiller is not connected to an RS485
communications loop, set the address switches as
follows: Hi = 0; Lo = 1.
If network operation is required, refer to the separate
Installation Manual accompanying the Network Master
Panel.
Control switches—Before applying power to the unit, verify that the Unit System Switch is in the stop
position and that each Circuit Switch is in the Pumpdown and Stop position. If an optional Remote Stop
Switch is installed, it should be in the run position.
Ribbon cables—Make sure the field wiring for all flow switches, interlocks, or jumpers matches the
connections detailed on the field wiring drawing at the end of this manual. Check the ribbon cables that
connect the keypad, ADI board and output board to the controller. They should be fully seated with the
locking tabs engaged.