Basic Control SiUS34-907
34 Function
2.3 Electronic Expansion Valve PI Control
Main Electronic Expansion Valve EV1 Control
Carries out the electronic expansion valve (Y1E) PI control 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 37°F, but varies depending on the
discharge pipe superheated degree of inverter compressor.
Subcooling Electronic Expansion Valve EV3 Control
Makes PI control of the electronic expansion valve (Y3E) to keep the superheated degree (SH) of the outlet gas
pipe on the evaporator side for the full use of the subcooling heat exchanger.
SH = Ts1 - Te SH : Evaporator outlet superheated degree (°F)
Ts1 : Suction pipe temperature detected by thermistor R3T (°F)
Te : Low pressure equivalent saturation temperature (°F)
SH = Tsh -Te SH : Outlet superheated degree of evaporator (°F)
Tsh : Subcooling heat exchanger gas pipe temperature detected with the thermistor R6T (°F)
Te : Low pressure equivalent saturation temperature (°F)
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