Service Manual

Special Control SiUS281811E
82 Part 4 Functions and Control
3.2.2 Oil Return Control in Heating
Pc: High pressure sensor detection value
Pe: Low pressure sensor detection value
Tc: High pressure equivalent saturation temperature
Te: Low pressure equivalent saturation temperature
Ts1: Suction pipe temperature detected by thermistor R3T
Tb : Heat exchanger temperature
Starting conditions
Referring to the set conditions for the following items, start oil return control in heating.
 Integrated amount of displaced oil
 Timer setting (After the power is turned ON, integrated operating time is two hours and
subsequently every eight hours.)
In addition, integrated amount of displaced oil is derived from Tc, Te, and compressor load.
 Between (A) oil return preparation control and (B) oil return control, and between (B) oil return
control and (C) control after oil return, the compressor stops for 1 minute to reduce noise on
changing of the four way valve.
Outdoor unit
actuator
Electric Symbol
(A) Oil return preparation
control
(B) Oil return control (C) Control after oil return
18/24
class
30/36/42/48
class
Compressor M1C M1C Upper limit control 140 Hz Full load Increases 2 steps every 20
seconds from minimum
frequency until Pc – Pe >
0.4 MPa (58 psi) is
achieved.
Outdoor fan M1F M1F
M2F
STEP 8 OFF STEP 8
Main electronic
expansion valve
Y1E Y1E SH control 480 pulse (Fully open) 55 pulse
Subcooling
electronic
expansion valve
— Y3E 0 pulse 0 pulse 0 pulse
Four way valve Y1S Y1S ON OFF ON
Hot gas bypass
valve
Y2S — OFF OFF OFF
Ending conditions 2 minutes
x 12 minutes
x
Ts1 – Te < 5°C (9°F)
x Tb > 11°C (51.8°F)
OR
&
x 160 seconds
x
Pc – Pe > 0.4 MPa
(58 psi)
OR
Indoor unit actuator Heating oil return control
Fan
Thermostat ON unit OFF
Non-operating unit OFF
Thermostat OFF unit OFF
Electronic expansion valve
Thermostat ON unit 416 pulse
Non-operating unit 256 pulse
Thermostat OFF unit 416 pulse