Refrigerant Circuit Part; Refrigerant Circuit; Rzq18·24·30Pvju - Daikin FCQ18PVJU Service Manual

SiUS28-902_a

1. Refrigerant Circuit

1.1 RZQ18·24·30PVJU
No. in
refrigerant
Symbol
system
diagram
A M1C Inverter compressor (INV.)
M1F
D Inverter fan
Electronic expansion valve
E Y1E
(Main: EV1)
G Y1S Solenoid valve (Hot gas: SVP) Prevents the low pressure from transient falling.
Solenoid valve (Receiver gas
J Y2S
discharging: SVG)
M Y3S Four-way valve
N S1NPH High pressure sensor
O S1NPL Low pressure sensor
HP pressure switch (For INV.
P S1PH
compressor)
S — Fusible plug
Pressure regulating valve 1
T —
(Receiver to discharge pipe)
1 R1T Thermistor (Outdoor air: Ta)
Thermistor (INV. discharge
2 R2T
pipe: Tdi)
Thermistor (Suction pipe: Ts1) Detects suction pipe temperature, keep the suction superheated degree constant in
3 R3T
Thermistor (Heat exchanger
4 R4T
deicer: Tb)
5 R5T Thermistor (Suction pipe: Ts2) Calculates the internal temperature of the compressor.
Refrigerant Circuit
Name
Inverter compressor is operated on frequencies between 52 Hz and 177 Hz by using
the inverter.
17 steps
Since the system is of air heat exchanging type, the fan is operated at 8-step rotation
speed by using the inverter.
While in heating operation, PI control is applied to keep the outlet superheated degree
of air heat exchanger constant.
Collects refrigerant to receiver.
Switches the operation mode between cooling and heating.
Detects high pressure.
Detects low pressure.
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.
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.
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.
Detects outdoor temperature, correct discharge pipe temperature, and other functions.
Detects discharge pipe temperature, make the temperature protection control of
compressor, and others.
heating operation, and other functions.
Detects liquid pipe temperature of air heat exchanger, determine defrosting operation,
and other functions.
Refrigerant Circuit
Major Function
12