SiUS30-604 Normal Control
Function 67
5.2 Electronic Expansion Valve 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
outside unit heat exchanger (evaporator).
The optimum initial value of the evaporator outlet superheated degree is 41°F, but varies
depending on the discharge pipe superheated degree of inverter compressor.
Sub-cooling Electronic Expansion Valve EV3 Control
[Cooling operation]
Makes PI control of the electronic expansion valve (Y3E) to keep the superheated degree of the
outlet gas pipe on the evaporator side for the full use of the sub-cooling heat exchanger.
[Heating operation]
To lower the discharge
temperature
when the discharge
temperature
is over 203
°F, m
akes PI control
of the electronic expansion valve (Y3E) to keep the superheated degree of the outlet gas pipe on
the evaporator side for the full use of the sub-cooling heat exchanger. (When the discharge
temperature is lower than 203
°F, EV3 opening is 0 pulse.)
SH = Ts - Te SH : Evaporator outlet superheated degree (°F)
Ts : Suction pipe temperature detected by thermistor
R2T (°F)
Te : Low pressure equivalent saturation temperature
(°F)
SH = Tsh -Te SH : Outlet superheated degree of evaporator (°F)
Tsh : Suction pipe temperature detected with the
thermistor R5T (°F)
Te : Low pressure equivalent saturation temperature
(°F)
SH = Tsh -Te SH : Outlet superheated degree of evaporator (°F)
Tsh : Suction pipe temperature detected with the
thermistor R5T (°F)
Te : Low pressure equivalent saturation temperature
(°F)
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