Service manual

Special Control SiUS28-902_a
23 Function
3.2.2 Oil Return Operation in Heating Operation
[Conditions to start]
The heating oil-returning operation is started under the following conditions:
 Integrated amount of displaced oil
 Timer
(After the power is turned on, integrated operating-time is 2 hours and subsequently every 8
hours.)
In addition, the integrated amount of displaced oil is derived from Tc, Te, and the
compressor load.
* From the preparation of the oil-returning operation to the oil-returning operation, and from the
oil-returning operation to the operation after oil-returning, the compressor stops for 1 minute to
reduce noise when changing the position of the four-way valve.
Outdoor Unit Actuator
Oil return preparation
operation
Oil return operation Post-oil-return operation
Compressor Upper limit control 124 Hz
2-step increase from
52 Hz to
(Pc - Pe>58 psi) time
Outdoor unit fan STEP 8 OFF STEP 8
Four-way valve ON OFF ON
Main electronic expansion valve
(EV1)
SH control 1400 pls 200~400 pls
Subcooling electronic expansion
valve (EV2)
0 pls 0 pls 0 pls
Hot gas bypass valve (SVP) OFF ON ON
Receiver gas discharging valve
(SVG)
ON ON OFF
Ending conditions 130 sec.
• 6 min.
• Ts - Te<5
• 160 sec.
• Pc - Pe>58 psi
or
or
Indoor unit actuator Heating oil return operation
Fan
Thermostat ON unit OFF
Stopping unit OFF
Thermostat OFF unit OFF
Electronic expansion valve
Thermostat ON unit 500 pls
Stopping unit 500 pls
Thermostat OFF unit 500 pls