Daikin BSVQ36MVJU, Service Manual

Page: 51 / 312

Refrigerant Circuit SiUS30-604
38 Refrigerant Circuit
1. Refrigerant Circuit
1.1 RWEYQ60MTJU / RWEYQ72MTJU / RWEYQ84MTJU
No. in
refrigerant
system
diagram
Symbol Name Major Function
A M1C Inverter compressor (INV)
Inverter compressor is operated on frequencies between 52 Hz and 230 Hz by
using the inverter. The number of operating steps is as follows.
E Y1E
Electronic expansion valve
(Main: EV1)
In cooling operation: High pressure control
In heating or simultaneous cooling/heating operation:
When the heat exchanger is used as the evaporator : SH control
When the heat exchanger is used as the condenser : High pressure control
G Y3E
Electronic expansion valve
(Subcool: EV3)
PI control is applied to keep the outlet superheated degree of sub-cooling heat
exchanger constant.
H Y1S Solenoid valve (Hot gas: SVP)
Used to prevent the low pressure from transient falling.
I Y2S
Solenoid valve (Oil return of water
heat exchanger: SVE)
Used to collect the refrigerant oil from water heat exchanger.
J Y3S
Solenoid valve (Receiver gas
charging: SVL)
Used to maintain high pressure while in cooling operation at low water
temperature. And also used to prevent the accumulation of refrigerant in non-
operating outside units in the case of multiple-outside-unit system.
K Y4S
Solenoid valve (Receiver gas
discharging: SVG)
Used to collect refrigerant to receiver.
M Y5S
4-way selector valve
(Main: 20S1)
Changes the operation into cooling, heating or simultaneous cooling/heating
operation.
O Y6S
Solenoid valve (Non-operating unit
liquid pipe closing: SVSL)
Used to prevent the accumulation of refrigerant in non-operating outside units in
the case of multiple-outside-unit system.
P Y7S
4-way selector valve
(Sub: 20S2)
Changes the water heat exchanger into condenser or evaporator.
Q S1NPH High pressure sensor
Used to detect high pressure.
R S2NPL Low pressure sensor
Used to detect low pressure.
S 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 580psi or more to stop the compressor
operation.
V – 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.
W –
Pressure regulating valve 1 (Liquid
pipe to discharge pipe)
This valve opens at a pressure of 580psi 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.
2 R2T Thermistor (Suction pipe: Ts)
Used to detect suction pipe temperature, keep the suction superheated degree
constant in heating operation, and others.
3 R3T Thermistor (INV discharge pipe: Tdi)
Used to detect discharge pipe temperature, make the temperature protection
control of compressor, and others.
6 R4T
Thermistor (Heat exchanger gas pipe:
Tg)
Used to detect gas pipe temperature of water heat exchanger.
7 R5T
Thermistor (Sub-cooling heat
exchanger outlet pipe: Tsh)
Used to detect gas pipe temperature on the evaporation side of sub-cooling heat
exchanger, keep the superheated degree at the outlet of sub-cooling 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-outside-unit
system, and others.