Carrier 38VMA Series, Service Manual, Page: 10 / 112

Table 3 - 38VMA072, 096, 120,144HDS
No. in refrigerant
system diagram
Symbol Name Major Function
A INV Inverter compressor
Inverter compressor is operated on frequencies between 20 Hz and 100 Hz.
B INV1 Inverter compressor
C Heat exchanger To exchange heat with ambient environment.
D FAN A Left Inverter fan The fan is operated at 13-step rotation speed by using the inverter.
E FAN B Right Inverter fan The fan is operated at 13-step rotation speed by using the inverter.
F EXV A Electronic expansion valve Used to adjust refrigerant volume.
G EXV B Electronic expansion valve Used to adjust refrigerant volume.
H EXV C Electronic expansion valve Used to adjust sub-cooling.
I PHE Plate Heat Exchanger Used for sub-cooling liquid refrigerant from the electronic expansion valve.
J SV4 Solenoid valve Used to balance the oil between modules.
K SV7 Solenoid valve
This valve opens at a pressure of 565.6 psi to prevent pressure from
increasing.
L ST1 4-way valve Used to switch the operation mode between cooling and heating.
M H-LY1 High pressure sensor Used to detect high pressure.
N L-LY1 Low pressure sensor Used to detect low pressure.
O H-PRO High pressure switch
Used to protect the system pressure. When system pressure is too high, the
pressure switch will open. Once the pressure switch is open, compressor
will stop and will restart after 12 minutes.
P L-PRO Low pressure switch
Used to protect the system pressure. When the system pressure is too low,
the pressure switch will open. Once the pressure switch is open,
compressor will stop, and will restart after 12 minutes.
Q Pressure regulating valve
This valve opens at a pressure of 580 psig to prevent pressure from
increasing, thus resulting in no damage to functional parts due to the
increase of pressure in transportation or storage.
R Oil separator
Used to separate oil from high pressure and high temperature refrigerant,
which is pumped out during compression.
S Accumulator
Used to store the liquid refrigerant and oil. It can protect the compressor
from liquid slugging.
T T3 Thermistor (outdoor coil deicer)
Used to detect liquid pipe temperature of ODU heat exchanger, determine
defrosting operation, and others.
1 T4 Thermistor (Outdoor air) Used to detect outdoor / ambient temperature.
2 T5 Thermistor (liquid pipe) Detects temperature of liquid pipe after Plate Heat Exchanger.
3 T6
Thermistor (Plate Heat
Exchanger gas pipe)
Detects temperature of gas pipe on the evaporation side of Plate Heat
Exchanger. Used to maintain constant control on superheated of the Plate
Heat Exchanger.
4 T7 Thermistor (Accumulator outlet) Used to detect gas pipe temperature at the accumulator outlet.
5 INV Gas Thermistor (INV discharge pipe)
Used to detect discharge pipe temperature. Enables the temperature
protection control of compressor, and others.
6 INV1 Gas Thermistor (INV1 discharge pipe)
Used to detect discharge pipe temperature. Enables the temperature
protection control of compressor, and others.
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