16.AUXILIARY FUNCTIONS
Example:
Suction 1 operating with 2 compressors, 2 external thermostats and 1 individual thermostat:
Suction 1:
1.2.x.2
Pressure setpoint: 50,0 psi
1.2.x.4
On / Off compressor hysteresis: 10 psi
1.2.x.15
Number of compressors: 2
1.2.x.22
Modulation of compressor 1: On/Off
1.2.x.23
Modulation of compressor 2: On/Off
1.2.x.37
Compressor 1 main output: O1
1.2.x.38
Compressor 2 main output: O2
Pump Down for group 1:
1.7.x.1.1
Enables Pump Down: Yes
1.7.x.1.2
Pump Down Setpoint: 5.0 psi
1.7.x.1.3
Maximum time for Pump Down: 5 minutes
1.7.x.1.4
Digital Output: O3
External thermostats (auxiliary inputs 1 and 2):
Input 1:
1.6.x.1
Pressure switch: Suction 1
1.6.x.2
Input function: Activates Pump Down
1.6.x.4
Digital input address: I1
Input 2:
1.6.x.1
Pressure switch: Suction 1
1.6.x.2
Input function: Activates Pump Down
1.6.x.4
Digital input address: I2
Individual Thermostat:
1.7.6.x.1
Operating mode: Cooling
1.7.6.x.2
Temperature setpoint: 5°C
1.7.6.x.7
Linked pressure switch: Suction 1
1.7.6.x.9
Main output: O4
In this example, the Suction 1 control enters the Pump Down process if digital inputs I1 and I2 are actuated and Output O4 is off. (External thermostats
requesting Pump Down and Internal thermostat below the setpoint).
After the last compressor has been switched off, the compressor operation remains blocked until any of the thermostats is in demand for refrigeration.
(Inputs I1 or I2 off or Output O4 on).
I1
I2
O4
PD
Operating
thermostat
Pump Down
Process
Compressor C1
activating point
Suction pressure
Suction
Setpoint
Pump Down
Setpoint
Compressor 1
Pump Down
Output
Compressor 1
Shutdown
Valve
closing
Valve opening and
compressor release
32
