Basic Control SiBE18-821_C
80 Function
2.3 Electronic Expansion Valve PI Control
Main Electronic Expansion Valve
The PI control of electronic expansion valve (Y1E) is carried out to maintain the evaporator
outlet superheated degree (SH) at constant during heating operation to make maximum use of
the outdoor unit heat exchanger (evaporator).
The optimum initial value of the evaporator outlet superheated degree is 3°C, but varies
depending on the discharge pipe superheated degree of inverter compressor.
Subcooling Electronic Expansion Valve
The PI control of electronic expansion valve (Y3E) is carried out to keep the evaporator outlet
superheated degree
(SH)
of gas pipe for the full use of the subcooling heat exchanger.
SH = Ts1 – Te SH : Evaporator outlet superheated degree (°C)
Ts1 : Suction pipe temperature detected by
thermistor R3T (°C)
Te : Low pressure equivalent saturation temperature
(°C)
SH = Tsh – Te SH : Evaporator outlet superheated degree (°C)
Tsh : Subcooling heat exchanger gas pipe
temperature detected by thermistor R6T (°C)
Te : Low pressure equivalent saturation temperature
(°C)
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