Electronic Expansion Valve Pi Control - Daikin SkyAir RZR-TA Series Service Manual

Basic Control
2.3

Electronic Expansion Valve PI Control

Main Electronic Expansion Valve Control
Carries out main electronic expansion valve (Y1E) PI control to maintain the evaporator outlet
superheated degree (SH) at constant during heating operation, thus making maximum use of the
outdoor heat exchanger (evaporator).
SH = Ts1 – Te
The optimum initial value of the evaporator outlet superheated degree is 3°C (5.4°F), but varies
depending on the discharge pipe superheated degree of inverter compressor.
Subcooling Electronic Expansion Valve Control
Carries out PI control of subcooling 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 = Tsh – Te
108
SH: Evaporator outlet superheated degree
Ts1: Suction pipe temperature detected by thermistor
R3T
Te: Low pressure equivalent saturation temperature
SH: Evaporator outlet superheated degree
Tsh: Subcooling heat exchanger gas pipe temperature
detected by thermistor R6T
Te: Low pressure equivalent saturation temperature
SiUS281811EA
Part 4 Functions and Control