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SiUS28-902_B
Special Control
Function
21
3.4
Pump Down Residual Operation
Pe: Low pressure sensor detection value
Td: Discharge pipe temperature
When activating compressor, if the liquid refrigerant remains in the heat-exchanger, the liquid
enters into the compressor and dilutes oil therein resulting in decrease of lubricity.
Therefore, the pump down residual operation is performed to collect the refrigerant in the heat-
exchanger when the compressor is down.
3.4.1 Pump Down Residual Operation in Cooling
3.4.2 Pump Down Residual Operation in Heating
3.5
Restart Standby
Ta : Outdoor air temperature
Restart is stood by force to prevent frequent power-on/off and to equalize pressure in the
refrigerant system.
Actuator
Master unit operation
Compressor
124 Hz
Outdoor unit fan
Fan control
Four-way valve
OFF
Main electronic expansion valve (EV1)
2000 pls
Hot
-
gas bypass valve (SVP)
OFF
Receiver gas discharging valve (SVG)
ON
OFF
Ending conditions
30 seconds
Pe < 73 psi
Td > 230
F
OR
Actuator
Master unit operation
Compressor
124 Hz
Outdoor unit fan
STEP 8
Four-way valve
ON
Main electronic expansion valve (EV1)
0 pls
Hot
-
gas bypass valve (SVP)
OFF
Receiver gas discharging valve (SVG)
ON
OFF
Ending conditions
3 minutes
Pe < 36 psi
Td > 230
F
OR
Actuator
Operation
Remarks
Compressor
OFF
Outdoor unit fan
Ta > 86
F: STEP 4
Ta
86
F: OFF
Four-way valve
Keep former condition.
Main electronic expansion valve (EV1)
0 pls
Hot
-
gas bypass valve (SVP)
ON
Receiver gas discharging valve (SVG)
OFF
Ending conditions
5 minutes