Daikin ALTHERMA HT EKBUHAA6 V3, Service Manual

Page: 69 / 302

ESIE09-08A Basic Control
Function 57
2.3
Electronic Expansion Valve PI Control R-410A
circuit
Main Electronic Expansion Valve EV1 Control - Outdoor Unit
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 3°C, but varies depending on the
discharge pipe superheated degree of inverter compressor.
Subcooling Electronic Expansion Valve EV3 Control - Outdoor Unit
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.
Electronic Expansion Valve K1E Control - Indoor Unit
Carries out the electronic expansion valve (K1E) PI control to maintain the condensor outlet subcooled
degree (SC) at constant during heating operation to make maximum use of the indoor unit heat exchanger
(condensor).
2.4
Electronic Expansion Valve PI Control R-134a
circuit
Electronic Expansion Valve K2E Control - Indoor Unit
Carries out the electronic expansion valve (K1E) PI control to maintain the condensor outlet subcooled
degree (SC) at constant during heating operation to make maximum use of the indoor unit heat exchanger
(condensor).
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 : Outlet superheated degree of evaporator (

C)
Tsh : Suction pipe temperature detected with the
thermistor R4T (

C)
Te : Low pressure equivalent saturation temperature (

C)
SC = Tc - R3T
SC = Tc - R7T