Electronic Expansion Valve Pi Control - Daikin RTSQ20PY1 Service Manual

SiBE31-801_C
6.3

Electronic Expansion Valve PI Control

6.3.1 Electronic Expansion Valve of Outdoor Unit
Main electronic expansion valve (Y1E)
When the outdoor unit heat exchanging is performed via the evaporator (20SA is set to ON),
this function is used to exert PI control on the electronic expansion valve (Y1E) so that the
evaporator outlet superheated degree (SH) will become constant.
SH = Tg - Te
Refrigerant charge electronic expansion valve (Y2E)
While in automatic refrigerant charge and additional refrigerant charge mode, this function is
used to exert PI control on the opening degree of the electronic expansion valve (Y2E) in
response to outdoor temperature and close the valve after the completion of refrigerant charge.
For normal operation, this electronic expansion valve opening is 80 pls.
Subcooling electronic expansion valve (Y3E)
In order to make the maximum use of the subcooling heat exchanger, this function is used to
exert PI control on the electronic expansion valve (Y3E) so that the evaporator-side gas pipe
superheated degree (SH) will keep constant.
SH = Tsh - Te
6.3.2 Electronic Expansion Valve of Function Unit
Liquid injection electronic expansion valve (Y1E)
This electronic expansion valve (Y1E) operates under the PI control so that the compressor
discharge pipe superheated degree (DSH) will be kept constant in heating operation at low
outdoor temperature.
DSH = HTdik - Tck
Function
SH: Evaporator outlet superheated degree
(°C)
Tg : Gas pipe temperature (°C) detected by
the heat exchanger gas pipe thermistor
R2T.
Te : Low pressure equivalent saturated
temperature (°C)
SH : Evaporator outlet superheated degree
(°C)
Tsh: Gas pipe temperature (°C) detected by
the subcooling heat exchanger outlet
thermistor R5T
Te : Low pressure equivalent saturated
temperature (°C)
DSH : Discharge pipe superheated degree
(°C)
HTdik:Discharge pipe temperature (°C)
Tck : High pressure equivalent saturation
temperature (°C)
Normal Operation
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