Pumpdown Mode; Fan Speed / Gas Cooler Control; Figure 33: Controller Logic For The Pumpdown Function With Factory Settings - Emerson Copeland OME-4MTL-12X Application Manuallines

Parameter Description
SETC1 Compressor Circuit 1 setpoint
Differential to be subtracted from
SPF1
the compressor setpoint
Compressor capacity during
SPF2
pumpdown
SPF3 Pumpdown maximum time
SPF4 Automatic pumpdown
SPF5 Pumpdown offset
Table 17: Pumpdown parameters

2.11.2 Pumpdown mode

The pumpdown function of the CO
standard refrigerants. Based on the ambient temperature and the compressor setpoint, the controller
calculates two different pumpdown setpoints:
▪ setpoint based on ambient temperature = T
▪ setpoint based on compressor setpoint = SETC1 – SPF1
The lowest pumpdown setpoint will always be applied. The following diagram illustrates the controller
logic:
Ambient condition:
T = 20 °C
Amb
SPF5 = 20 K
Pumpdown setpoint based
on ambient temperature:
– SPF5 = 0 °C
T
Amb

Figure 33: Controller logic for the pumpdown function with factory settings

NOTE: The pumpdown setpoint will never be lower than allowed by parameter RC02, ie,
-25 °C, reached when T

2.11.3 Fan speed / gas cooler control

2.11.3.1 Subcritical operation
Typically, with gas cooler outlet temperatures below 27 °C (B7 = AIC7 < GC1 - GC2), the system
operates in subcritical mode.
▪ The CO
refrigerant condenses inside the gas cooler.
2
▪ The gas cooler outlet temperature is read by the probe AIC7 (= B7), which defines the fan speed.
▪ The gas cooler valve HPV will keep a certain sub-cooling of the refrigerant (about 2-3 K) in order
to create pressure differential between the gas cooler and the flash tank.
▪ The fan speed setpoint (related to the gas cooler outlet temperature) is +5 °C with a proportional
band of +5 K (setpoint ± 2.5 K). In other words, above 7.5 °C, the fan will always run at full speed,
while below 2.5 °C, the fan will always run at minimum speed.
SETF1 Gas cooler Circuit 1 setpoint
Range: +5 to +25 °C
Unit: (°C)
26
refrigeration unit does not work in the same way as in units using
2
Amb
-18 °C < 0 °C
Controller will perform
pumpdown down to -18 °C
= -5 °C.
Amb
Level Min value Max value
Pr1 -15 °C
Pr1 0 K
0 %
Pr1 (min speed (max speed
25 Hz)
Pr1 0 min
Pr1
Pr2 0 K
– SPF5
Compressor setpoint:
SETC1 = -10 °C
SPF1 = 8 K
Pumpdown setpoint based on
compressor setpoint:
SETC1 – SPF1 = -18 °C
AGL_Unit_OME_4MTL_EN_Rev01
Factory
setting
-5 °C -10 °C
20 K 8 K
100 %
0 %
60 Hz)
25 min 3 min
yes
40 K 20 K