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