Panasonic U-4..6ML5XPQ, Service Manual

Page: 54 / 283

Refrigerant Circuit
42 Refrigerant Circuit
U-4, 5, 6ML5DPQ
No. in
refrigerant
system
diagram
Symbol Name Major Function
A M1C Inverter compressor (INV)
Inverter compressor is operated on frequencies between 36 Hz and 195 Hz by using
the inverter.
31 steps
D
M1F
M2F
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 Y3E
Electronic expansion valve
(Subcool: EV3) Pl control is applied to keep the outlet superheated degree of subcooling heat
exchanger constant.
G Y2S Solenoid valve (Hot gas: SVP) Used to prevent the low pressure from transient falling.
H Y3S
Solenoid valve (Unload circuit
SVUL)
Used to the unloading operation of compressor.
M Y1S Four 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 4.0 MPa or more to stop the compressor
operation.
T —
Pressure regulating valve 1
(Receiver to discharge pipe)
This valve opens at a pressure of 4.0 MPa 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) Used to detect outdoor temperature, correct discharge pipe temperature, and others.
2 R2T
Thermistor (INV discharge
pipe: Tdi) used to detect discharge pipe temperature, make the temperature protection control of
compressor, and others.
3 R3T
Thermistor
(Suction pipe1: Ts1) used to detect suction pipe temperature, keep the suction superheated degree
constant in heating operation, and others.
4 R4T
Thermistor (Heat exchanger
deicer: Tb) Used to detect liquid pipe temperature of air heat exchanger, determine defrosting
operation, and others.
5 R5T
Thermistor
(Suction pipe2: Ts2)
Used to the calculation of an internal temperature of compressor etc.
6 R6T
Thermistor (Subcooling heat
exchanger gas pipe: Tsh)
Used to control of subcooling electronic expansion valve.
7 R7T
Thermistor
(Liquid pipe1: Tl1)
Used to detect refrigerant over charge in check operation, and others.
8 R8T
Thermistor
(Liquid pipe2: Tl2)
Used to detect refrigerant over charge in check operation, and others.
Urban Multi ML5 · Mini UM · Heat Pump