SiUS34-907 Special Control
Function 37
3.2 Oil Return Operation
In order to prevent the compressor from running out of oil, the oil return operation is conducted to recover oil
flown out from the compressor to the system side.
3.2.1 Oil Return Operation in Cooling Operation
[Start conditions]
Referring to the set conditions for the following items, start the oil-return operation in cooling.
• Cumulative oil feed rate
• Timer setting (Make this setting to start the oil-return operation when the initial cumulative operating time
reaches two hours after power supply is turned ON and then every eight hours.)
The cumulative oil feed rate is computed from Tc, Te, and compressor loads.
Outdoor unit actuator
Oil return preparation
operation
Oil return operation Post-oil-return operation
Compressor
Take the current step as the
upper limit.
52 Hz Full load
(→ Low pressure constant
control)
Same as the “oil return
operation” mode.
Outdoor unit fan Fan control (Normal cooling) Fan control (Normal cooling) Fan control (Normal cooling)
Four-way valve (Y1S) OFF OFF OFF
Main electronic expansion valve (EV1) 480 pls 480 pls 480 pls
Subcooling electronic expansion valve
(EV3)
SH control 0 pls 0 pls
Hot gas bypass valve (SVP) OFF OFF OFF
Ending conditions 20 sec.
• 3 min.
• Ts - Te<41°F
• 3 min.
• Pe<87 psi
• HTdi>230°F
Indoor unit actuator Cooling oil return operation
Fan
Thermostat ON unit Remote controller setting
Stopping unit OFF
Thermostat OFF unit Remote controller setting
Electronic expansion valve
Thermostat ON unit Normal opening
Stopping unit 224 pls
Thermostat OFF unit Normal opening with forced thermostat ON
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