Service manual

SiUS28-902_a Refrigerant Circuit
Refrigerant Circuit 12
1. Refrigerant Circuit
1.1 RZQ18·24·30PVJU
No. in
refrigerant
system
diagram
Symbol Name Major Function
A M1C Inverter compressor (INV.)
Inverter compressor is operated on frequencies between 52 Hz and 177 Hz by using
the inverter.
17 steps
D
M1F
Inverter fan
Since the system is of air heat exchanging type, the fan is operated at 8-step rotation
speed by using the inverter.
EY1E
Electronic expansion valve
(Main: EV1)
While in heating operation, PI control is applied to keep the outlet superheated degree
of air heat exchanger constant.
G Y1S Solenoid valve (Hot gas: SVP) Prevents the low pressure from transient falling.
JY2S
Solenoid valve (Receiver gas
discharging: SVG)
Collects refrigerant to receiver.
M Y3S Four-way valve Switches the operation mode between cooling and heating.
N S1NPH High pressure sensor Detects high pressure.
O S1NPL Low pressure sensor Detects low pressure.
PS1PH
HP pressure switch (For INV.
compressor)
Prevents the increase of high pressure when a malfunction occurs, this switch is
activated at high pressure of 580 psi or more to stop the compressor operation.
S — Fusible plug
Prevents the increase of pressure when abnormal heating is caused by fire or other
heat factors, the fusible part of the plug is molten at a temperature of 158 to 167°F to
release the pressure into the atmosphere.
T—
Pressure regulating valve 1
(Receiver to discharge pipe)
This valve opens at a pressure of 290 to 390 psi for prevention of pressure increase,
thus resulting in no damage of functional parts due to the increase of pressure in
transportation or storage.
1 R1T Thermistor (Outdoor air: Ta) Detects outdoor temperature, correct discharge pipe temperature, and other functions.
2R2T
Thermistor (INV. discharge
pipe: Tdi)
Detects discharge pipe temperature, make the temperature protection control of
compressor, and others.
3 R3T Thermistor (Suction pipe: Ts1)
Detects suction pipe temperature, keep the suction superheated degree constant in
heating operation, and other functions.
4R4T
Thermistor (Heat exchanger
deicer: Tb)
Detects liquid pipe temperature of air heat exchanger, determine defrosting operation,
and other functions.
5 R5T Thermistor (Suction pipe: Ts2) Calculates the internal temperature of the compressor.