Service Manual

SiUS181631EA Special Control
Functions and Control 57
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
Conditions to start
Oil return operation in cooling operation is started referring to the following conditions:

Cumulative oil feed rate

Timer setting (Make this setting so as to start the oil return operation when the initial cumulative
operating time reaches 2 hours after power supply is turned ON and then every 8 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 in
oil return
operation mode.
Outdoor fan Fan control (Normal cooling) Fan control (Normal cooling) Fan control (Normal cooling)
Four way valve (Y1S) OFF OFF OFF
Main electronic expansion valve (Y1E) 480 pulse 480 pulse 480 pulse
Subcooling electronic expansion valve
(Y3E)
SH control 0 pulse 0 pulse
Hot gas bypass solenoid valve (Y2S) OFF OFF OFF
Ending conditions 20 sec.
•
3 min.
•
Ts1 – Te < 5
°
C
(9°F)
•
3 min.
•
Pe < 0.6 MPa
(201 ftAq)
•
HTdi > 110
°
C
(230°F)
or
or
Indoor unit actuator Cooling oil return operation
Indoor fan
Thermostat ON unit Remote controller setting
Stopping unit OFF
Thermostat OFF unit Remote controller setting
Electronic expansion valve of
BP unit
Thermostat ON unit SH control
Stopping unit 77 pulse
Thermostat OFF unit SH control