Basic Control SiUS181631EA
54 Functions and Control
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Compressors may operate in a pattern other than those listed in the above tables subject to the
operating conditions. Selection of full load operation to/from unload operation is made with the
unload circuit solenoid valve (Y3S). The full load operation is performed with the Y3S set to OFF,
while the unload operation is performed with the Y3S set to ON.
2.3 Electronic Expansion Valve PI Control
Main Electronic
Expansion Valve
The PI control of the main electronic expansion valve (Y1E) is carried out to keep the evaporator
outlet superheated degree (SH) constant during heating operation in order to make maximum use
of the outdoor unit heat exchanger (evaporator).
The optimum initial value of the evaporator outlet superheated degree is 3°C (5.4°F), but varies
depending on the discharge pipe superheated degree of the inverter compressor.
Subcooling
Electronic
Expansion Valve
The PI control of the subcooling electronic expansion valve (Y3E) is carried out to keep the
evaporator outlet superheated degree
(SH)
of the gas pipe in order to make maximum use of the
subcooling heat exchanger.
Step Full-load Unload Step Full-load Unload
1 36.0 Hz 16 110.0 Hz
2 39.0 Hz 17 116.0 Hz
3 43.0 Hz 18 122.0 Hz
4 47.0 Hz 19 128.0 Hz
5 52.0 Hz 20 134.0 Hz
6 52.0 Hz 57.0 Hz 21 140.0 Hz
7 57.0 Hz 64.0 Hz 22 146.0 Hz
8 62.0 Hz 71.0 Hz 23 152.0 Hz
9 68.0 Hz 78.0 Hz 24 158.0 Hz
10 74.0 Hz 25 164.0 Hz
11 80.0 Hz 26 170.0 Hz
12 86.0 Hz 27 175.0 Hz
13 92.0 Hz 28 180.0 Hz
14 98.0 Hz 29 185.0 Hz
15 104.0 Hz 30 190.0 Hz
31 195.0 Hz
SH = Ts1 – Te SH: Evaporator outlet superheated degree
Ts1: Suction pipe temperature detected by thermistor
R3T
Te: Low pressure equivalent saturation temperature
SH = Tsh – Te SH: Evaporator outlet superheated degree
Tsh: Subcooling heat exchanger gas pipe temperature
detected by thermistor R6T
Te: Low pressure equivalent saturation temperature
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