Daikin VRV IV-S RXTQ-TAVJU Series, Service Manual

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Refrigerant Circuit SiUS331604E
7 Refrigerant Circuit
1. Refrigerant Circuit
1.1 RXTQ36TAVJU
No. in
piping
diagram
Symbol Name Function
(1) M1C Inverter compressor
Inverter compressor is operated on frequencies between 36 Hz and 195 Hz by using the
inverter.
(2) M1F Inverter fan
Because the system is of an air heat exchange type, the fan is operated at 8-step rotation
speed by using the inverter.
(3) Y1E
Electronic expansion valve
(Main) While in heating operation, PI control is applied to keep the outlet superheated degree of
air heat exchanger constant.
(4) Y1S Four way valve Used to switch the operation mode between cooling and heating.
(5) Y2S Solenoid valve (Hot gas) Used to prevent the low pressure from transient falling.
(6) Y3S Solenoid valve (Unload circuit) Used for unloading operation of compressor.
(7) S1NPH High pressure sensor Used to detect high pressure.
(8) S1NPL Low pressure sensor Used to detect low pressure.
(9) S1PH High pressure switch
In order to prevent the increase of high pressure when an error occurs, this switch is
activated at high pressure of 4.0 MPa (580 psi) or more to stop the compressor operation.
(10) — Fusible plug
In order to prevent the increase of pressure when abnormal heating is caused by fire or
others, the fusible part of the plug is molten at a temperature of 70 ~ 75°C (158 ~ 167°F) to
release the pressure into the atmosphere.
(11) —
Pressure regulating valve
(Receiver to discharge pipe)
This valve opens at a pressure of 4.0 MPa (580 psi) or more for prevention of pressure
increase, thus resulting in no damage of functional parts due to the increase of pressure in
transportation or storage.
(12) R1T Thermistor (Outdoor air) Used to detect outdoor air temperature, correct discharge pipe temperature, and others.
(13) R2T Thermistor (Discharge pipe)
Used to detect discharge pipe temperature, make the temperature protection control of
compressor, and others.
(14) R3T Thermistor (Suction pipe 1)
Used to detect suction pipe temperature, keep the suction superheated degree constant in
heating operation, and others.
(15) R4T
Thermistor (Heat exchanger
deicer) Used to detect liquid pipe temperature of air heat exchanger, determine defrost operation,
and others.
(16) R5T Thermistor (Suction pipe 2) Used for calculation of internal temperature of compressor etc.
(17) R7T Thermistor (Liquid pipe) Used to detect refrigerant overcharge in check operation, and others.
(18) R10T Thermistor (Radiation fin)
• Used for outdoor unit fan speed control.
• Used for inverter radiation fin temperature control.
• Used for pressure difference control.