Special Control SiUS28-902_a
25 Function
3.4 Pump-down Residual Operation
When activating the compressor, if the liquid refrigerant remains in the heat-exchanger, the
liquid enters into the compressor and dilutes oil therein resulting in a 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 Operation
3.4.2 Pump-down Residual Operation in Heating Operation
Actuator Master unit operation
Compressor 124 Hz
Outdoor unit fan Fan control
Four-way valve OFF
Main electronic expansion valve (EV1) 2000 pls
Subcooling electronic expansion valve (EV2) 0 pls
Hot gas bypass valve (SVP) OFF
Receiver gas discharging valve (SVG) ON → OFF
Ending conditions
• 30 sec.
• Pe<73 psi
• Td>230°F
Actuator Master unit operation
Compressor 124 Hz
Outdoor unit fan STEP 8
Four-way valve ON
Main electronic expansion valve (EV1) 0 pls
Subcooling electronic expansion valve (EV2) 0 pls
Hot gas bypass valve (SVP) OFF
Receiver gas discharging valve (SVG) ON → OFF
Ending conditions
• 3 min.
• Pe<36 psi
• Td>230°F
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