Service Manual

Special Control SiUS181631EA
58 Functions and Control
3.2.2 Oil Return Operation in Heating Operation
Conditions to start
Oil return operation in heating operation is started referring to the following conditions:

Integrated amount of displaced oil

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 integrated amount of displaced oil is derived from Tc, Te, and the compressor load.
∗
From the preparation to the oil return operation, and from the oil return operation to the post-oil-
return operation, the compressor stops for 1 minute to reduce noise on changing of the four way
valve.
Outdoor unit actuator
Oil return preparation
operation
Oil return operation Post-oil-return operation
Compressor Upper limit control 140 Hz Full load
36 Hz Unload
+2 steps / 20 sec.
(until Pc - Pe > 0.4 MPa)
(134 ftAq)
Outdoor fan STEP 8 OFF STEP 8
Four way valve (Y1S) ON OFF ON
Main electronic expansion valve (Y1E) SH control 480 pulse 55 pulse
Subcooling electronic expansion valve
(Y3E)
0 pulse 0 pulse 0 pulse
Hot gas bypass solenoid valve (Y2S) OFF OFF OFF
Ending conditions 2 min.
•
12 min.
•
Ts1 – Te < 5°C
(9°F)
•
Tb > 11°C
(51.8°F)
•
160 sec.
•
Pc – Pe > 0.4 MPa
(134 ftAq)
or
&
or
Indoor unit actuator Heating oil return operation
Indoor fan
Thermostat ON unit OFF
Stopping unit OFF
Thermostat OFF unit OFF
Electronic expansion valve of
BP unit
Thermostat ON unit SH control
Stopping unit 80 pulse
Thermostat OFF unit SH control