CC7.8.9/0519/E
7/7
The pumpdown function of the CO
2
refrigeration unit does not work in the same way as in units using standard
refrigerants. Based on the ambient temperature and the compressor setpoint, the controller calculates two
different pumpdown setpoints:
▪
Setpoint based on ambient temperature = T
Amb
– SPF5
▪
Setpoint based on compressor setpoint = SETC1
– SPF1
The lowest pumpdown setpoint will always be applied. The following diagram illustrates the controller logic:
Figure 8: Controller logic for the pumpdown function
NOTE: The pumpdown setpoint will never be lower than what parameter RC02 allows.
-18°C < 0°C
Controller will perform
pumpdown down to
-18°C
Ambient condition:
T
Amb
= 20°C
SPF5 = 20K
Compressor setpoint:
SETC1 = -10°C
SPF1 = 8K
Pumpdown setpoint based
on ambient temperature:
T
Amb
– SPF5 = 0°C
Pumpdown setpoint based on
compressor setpoint:
SETC1
– SPF1
= -18°C
