Unit installation

OMRCPMICRO 25
Lead-Lag of Refrigerant Circuits
Automatic
The controller provides automatic lead-lag of refrigeration circuits. The circuit having the fewest number of
starts on all compressors in the circuit will be started first. Changes to circuit capacity will be made by
changing the position of the compressor unloaders when applicable. Compressors will be selected by
changing unloader status. This prevents short-cycling of compressors when the cooling load is low. If both
circuits are operating and a stage-down to one circuit is required, the circuit with the most operating hours will
cycle off first.
Manual
The operator may manually select the lead refrigerant circuit or have the controller automatically select the lead
refrigerant circuit to equalize compressor hours. Automatic lead-lag may be defeated by selecting circuit #1 or
circuit #2 as the lead circuit ("Lead Circuit" Menu 16).
Manual Operation
Manual operating modes are available to facilitate setup and troubleshooting of the unit. Any of the following
manual modes may be selected from the Control Mode Menu.
ManualOff: Manual unit off.
Auto1Off2: Automatic Circ #1, Circ #2 off.
Auto2Off1: Automatic Circ #2, Circ #1 off.
ManualStaging: Manual Staging, Circ #1 & 2.
Note: These manual settings are intended to aid in troubleshooting and should not be considered to
be normal operating modes. The equipment should not be left unattended during manual operation as
the automatic staging controls are disabled. The chiller will remain in the manual mode until
Automatic operation is selected.