Carrier 38VMA072RDS5-1, Engineering Data Book

Page: 23 / 176

23
Refrigerant Circuit Diagrams
Table 21 —Refrigerant Circuit
Name
Symbol
Major Function
Refrigerant Circuit
Diagram
Electrical Wiring
Diagram
Inverter
compressor
INV1 Compressor A
Varies the refrigerant flow rate by adjusting the frequency based on objective
pressure.
INV2 Compressor B
INV3 Compressor C
Oil separator O/S -
Separates oil from high pressure gas refrigerant, which is pumped out from
compressor.
Inverter fan
FANA
Regulates the heat exchanger capacity by adjusting rotating speeds based on the
operating pressure.
FANB
FANC
FAND
4-way valve ST1 Switches the operation mode between heating and cooling.
Solenoid valve
SV3A
Controls heat exchanger areas.
SV3B
SV3C
SV3D
SV3E
SV4 Controls amount of oil from the oil separator to compressor.
SV5
1) High-pressure-rise prevention.
2) Prevents bottom of heat exchangers from freezing in heating mode.
SV6
1) Supplies hot gas for heating indoor units in cooling main mode.
2) Bypasses hot gas from compressor discharge in heating operation.
SV8
SV7
1) Bypasses pressure at start-up stage and control capacity at low load condition.
2) High-pressure-rise prevention.
3) Discharge superheat protection.
Thermistor
T3A
Controls defrosting during heating operation.
T3C
T4 Detects outdoor air temperature and control fan speed.
T5 Control SV6 and SV8 based on refrigerant status in cooling main mode.
T6
Used for MDC to control EVXA and SVP.
T7
T7C1
Detects discharge temperature and calculates discharge superheat. T7C2
T7C3
Tpr1 TP1-PRO
Provides high-temperature protection. Tpr2 TP2-PRO
Tpr3 TP3-PRO
High pressure
sensor
PH H-YL1 Detects high pressure.
Low pressure
sensor
PL L-YL1 Detects low pressure.
High pressure
switch
HPS H-PRO-4
Prevents abnormal increase of high pressure, which will activate at 4.0MPa and shut
down compressors.