Electronic Expansion Valve Control - Daikin VRV-WIII RWEYQ72PTJU Service Manual

Normal Control
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
condensing unit heat exchanger (evaporator).
SH = Ts - Te
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.
Subcooling 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 subcooling heat exchanger.
SH = Tsh-Te
[Heating operation]
To lower the discharge pipe temperature when the discharge pipe temperature is over 203°F,
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 subcooling heat exchanger. (When the
discharge pipe temperature is lower than 203°F, EV3 opening is 0 pulse.)
SH = Tsh-Te
52
SH: Evaporator outlet superheated degree (°F)
Ts: Suction pipe temperature detected by thermistor
R2T (°F)
Te: Low pressure equivalent saturation temperature
(°F)
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: Outlet superheated degree of evaporator (F)
Tsh: Suction pipe temperature detected with the
thermistor R5T (F)
Te: Low pressure equivalent saturation temperature
(F)
SiUS30-1301
Function and Control