RSMD Technical Guide
SEQUENCE OF OPERATIONS
11
Head Pressure Control
Head Pressure Control
The Refrigeration System Module for Digital Compressors (RSMD)
can monitor a Head Pressure Transducer and control a Condenser
Fan to maintain a Head Pressure Setpoint. The RSMD must be
confi gured for an Air Cooled Condenser.
A Condenser Relay is commanded on when the fi rst compressor is
enabled (except if the unit is in Heat Pump Defrost Mode). On an
Air Cooled Unit, the Condenser Fan will be controlled with 0-10
VDC output signal.
When the Condenser Signal fi rst activates, it maintains at 100% for
10 seconds.
In the Cooling Mode, the Condenser Signal will modulate to maintain
the Cooling Head Pressure Setpoint. The signal can modulate
between 15% and 100%. If the Head Pressure exceeds 550 PSIG,
the condenser control signal will immediately go to 100% and a
High Head Pressure Alarm will be generated. The alarm will be
deactivated when the Head Pressure drops below 540 PSIG.
In the Dehumidifi cation Mode, the Condenser Output Signal controls
to the Reheat Head Pressure Setpoint. High Head Pressure conditions
produce the same eff ects as in the Cooling Mode.
If no Head Pressure Sensor is detected, the Condenser Output Signal
will be maintained at 100%.
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