Electronic Expansion Valve Pi Control - Daikin RXYQ72 Serivce Manual

Basic Control
2.3

Electronic Expansion Valve PI Control

Main Motorized Valve EV1 Control
Carries out the motorized 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).
SH = Ts - Te
The optimum initial value of the evaporator outlet superheated degree is 9°F, but varies depending
on the discharge pipe superheated degree of inverter compressor.
Subcooling Motorized Valve EV2 Control
Makes PI control of the motorized valve (Y2E) 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
38
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)
SiUS39-601
Function