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SEQUENCE OF OPERATIONS
Cooling Mode & Dehumidifi cation Operation
Cooling Mode Operation
In the Cooling Mode, as the Supply Air Temperature (SAT) rises
above the Active SAT Cooling Setpoint, the compressors will stage
on and modulate to maintain the Active Evaporator Coil Suction
(Saturated) Temperature Setpoint. Two compressors are controlled
per Refrigerant System Module (RSMD). Multiple RSMDs are
needed when there are more than two compressors
In units with one digital and one fi xed compressors, if the digital
compressor modulates to 100% and the SAT is still above the SAT
Cooling Setpoint for the Cooling Stage Up Delay, then the fi xed
compressor will stage on. The digital compressor will then be
allowed to modulate as necessary to maintain the Active Evaporator
Coil Suction (Saturated) Temperature Setpoint. Minimum off times
must also be met before compressors can stage on.
In units with multiple digital compressors, if the 1st digital
compressor modulates to 100% and the SAT is still above the SAT
Cooling Setpoint for the Cooling Stage Up Delay, then the 2nd digital
compressors will enable and the two digital Compressors will then
modulate together to maintain the Active Evaporator Coil Suction
(Saturated) Temperature Setpoint.
To stage down compressors, if the digital compressor(s) have
modulated down to 30% for the Stage Down Delay period and the
SAT has fallen below the SAT Cooling Setpoint minus the Stage
Control Window, then the last compressor to have staged on (digital
or Fixed) will stage off – assuming its Minimum Run Time has
been met. Any remaining digital compressors are then allowed to
modulate as needed. If the last remaining digital compressor reaches
0% for the Stage Down Delay, it will stage off .
10
Zone
Zone
Dehumidifi cation Operation
The RSMD activates the Cooling Stages based on the actual
Evaporator Coil Temperature compared to the Evaporator Coil
Suction (Saturation) Temperature Setpoint. The Evaporator Coil
Suction (Saturation) Temperature is calculated by using the Suction
Pressure Sensor and converting the pressure to temperature.
For Copeland Digital Scroll™ Compressor units, the RSMD will
modulate the Copeland Digital Scroll™ Compressor to maintain
the Evaporator Coil Suction (Saturation) Temperature Setpoint and
activate the Compressors as necessary.
On units that have one Digital and one Fixed Capacity Compressor,
if the Fixed Capacity Compressor is activated, the Copeland Digital
Scroll™ Compressor will only be allowed to modulate within the
range of 70% - 100% in order to prevent the loss of reheat capacity
during low load conditions. If, with both compressors on, the 1st
digital compressor has modulated down to its 70% minimum and
the Coil Suction Temperature falls below the Coil Temperature
Setpoint minus the Cooling Stage Control Window, then the second
compressor will stage off once its Compressor Minimum Run Time
and the Stage Down Delay Timers have been met. At that point, the
Copeland Digital Scroll™ Compressor can modulate down as needed
to maintain the Coil Temperature Setpoint.
If the RSMD has two Digital Compressors, the 1st Compressor will
be locked at 100% and the 2nd Compressor will modulate.
RSMD Technical Guide
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Troubleshooting
