Service Manual

Basic Control SiUS281811E
74 Part 4 Functions and Control
2. Basic Control
2.1 Normal Operation
Cooling Operation
Heating Operation
 Heating operation is not functional at an outdoor air temperature of 24CDB (75.2FDB)or more.
Outdoor unit
actuator
Electric Symbol
Operation Remarks
18/24
class
30/36/42/48
class
Compressor M1C M1C Compressor
PI control
Used for high pressure
protection control, low pressure
protection control, discharge
pipe temperature protection
control, and compressor
operating frequency upper limit
control with inverter protection
control.
Outdoor fan M1F M1F
M2F
Cooling fan control —
Main electronic
expansion valve
Y1E Y1E 480 pulse —
Subcooling
electronic expansion
valve
— Y3E PI control —
Four way valve Y1S Y1S OFF —
Hot gas bypass
valve
Y2S — OFF This valve turns ON with low
pressure protection control.
Outdoor unit
actuator
Electric Symbol
Operation Remarks
18/24
class
30/36/42/48
class
Compressor M1C M1C Compressor
PI control
Used for high pressure
protection control, low pressure
protection control, discharge
pipe temperature protection
control, and compressor
operating frequency upper limit
control with inverter protection
control.
Outdoor fan M1F M1F
M2F
Step 7 or 8 —
Main electronic
expansion valve
Y1E Y1E PI control —
Subcooling
electronic expansion
— Y3E PI control —
Four way valve Y1S Y1S ON —
Hot gas bypass
valve
Y2S — OFF This valve turns ON with low
pressure protection control.