Daikin RXYQ72, Serivce Manual

Page: 35 / 273

Refrigerant Circuit SiUS39-601
24 Refrigerant Circuit
1. Refrigerant Circuit
1.1 RXYQ72M, 96M
No. in
refrigerant
system
diagram
Symbol Name Major Function
A M1C Inverter compressor (INV) Inverter compressor is operated on frequencies between 52 Hz and 210 Hz by using the
inverter, while Standard compressor is operated with commercial power supply only. The
number of operating steps is as follows when Inverter compressor is operated in
combination with Standard compressor.
B M2C Standard compressor 1 (STD1)
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.
E Y1E
Electronic expansion valve
(Main: EV1) While in heating operation, PI control is applied to keep the outlet superheated degree of
air heat exchanger constant.
F Y2E
Electronic expansion valve
(Subcool: EV2) PI control is applied to keep the outlet superheated degree of subcooling heat exchanger
constant.
G Y1S Solenoid valve (Hot gas: SVP) Used to prevent the low pressure from transient falling.
H Y2S
Solenoid valve (Oil
equalization: SVO)
Used for oil equalizing among outdoor units in multiple-outdoor-unit system.
I Y3S
Solenoid valve (Receiver gas
charging: SVL)
Used to maintain high pressure while in cooling operation at low outdoor temperature.
And also used to prevent the accumulation of refrigerant in non-operating outdoor units in
the case of multiple-outdoor-unit system.
J Y4S
Solenoid valve (Receiver gas
discharging: SV)
Used to collect refrigerant to receiver.
K Y5S
Solenoid valve (Non-operating
unit gas discharging SVSG) Used to prevent the accumulation of refrigerant in non-operating outdoor units in the
case of multiple-outdoor-unit system.
L Y6S
Solenoid valve (Non-operating
unit liquid pipe closing: SVSL) Used to prevent the accumulation of refrigerant in non-operating outdoor units in the
case of multi-outdoor unit system.
M Y7S 4-way valve Used to switch the operation mode between cooling and heating.
N S1NPH High pressure sensor Used to detect high pressure.
O S1NPL Low pressure sensor Used to detect low pressure.
P S1PH
HP pressure switch (For INV
compressor)
In order to prevent the increase of high pressure when a malfunction occurs, this switch
is activated at high pressure of 550 psi or more to stop the compressor operation.
Q S2PH
HP pressure switch (For STD
compressor 2)
S — 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 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.
U —
Pressure regulating valve 2
(Liquid pipe to receiver)
V —
Pressure regulating valve 3
(Equalizing pipe to discharge
pipe)
1 R1T Thermistor (Outdoor air: Ta) Used to detect outdoor temperature, correct discharge pipe temperature, and others.
2 R2T Thermistor (Suction pipe: Ts)
used to detect suction pipe temperature, keep the suction superheated degree constant
in heating operation, and others.
3 R31T
Thermistor (INV discharge
pipe: Tdi)
used to detect discharge pipe temperature, make the temperature protection control of
compressor, and others.
4 R32T
Thermistor (STD1 discharge
pipe: Tds1)
6 R4T
Thermistor (Heat exchanger
deicer: Tb) Used to detect liquid pipe temperature of air heat exchanger, determine defrosting
operation, and others.
7 R5T
Thermistor (Subcooling heat
exchanger gas pipe: Tsh)
Used to detect gas pipe temperature on the evaporation side of subcooling heat
exchanger, keep the superheated degree at the outlet of subcooling heat exchanger
constant, and others.
8 R6T
Thermistor (Receiver outlet
liquid pipe: Tl) Used to detect receiver outlet liquid pipe temperature, prevent the drift between outdoor
units while in heating operation in the case of multiple-outdoor-unit system, and others.
9 R7T
Thermistor (Oil equalizing pipe:
To) Used to detect equalizing pipe temperature, opening/closing of the equalizing pipe stop
valve, and others.