Daikin Aurora Series, Service Manual

Page: 65 / 333

SiUS341802E Basic Control
Functions and Control 52
5.5 Electronic Expansion Valve PI Control
Main electronic expansion valve EVM control
When the outdoor unit heat exchanging is performed via the condenser (Y5S or Y6S is set to OFF),
this function is used to exert PI control on the electronic expansion valve (Y1E or Y3E) so that the
condenser outlet subcooled degree (SC) will become constant.
When the outdoor unit heat exchanging is performed via the evaporator (Y5S or Y6S is set to ON),
this function is used to exert PI control on the electronic expansion valve (Y1E or Y3E) so that the
evaporator outlet superheated degree (SH) will become constant.
Subcooling electronic expansion valve EVT control
In order to make the maximum use of the subcooling heat exchanger, this function is used to exert
PI control on the electronic expansion valve (Y2E, Y5E or Y3E) so that the evaporator-side gas
pipe superheated degree (SH) will become constant.
SC = Tc – Tf SC: Condenser outlet subcooled degree
Tc: High pressure equivalent saturated
temperature
Tf: Liquid pipe temperature detected by heat
exchanger liquid pipe thermistor R4T,
R5T
SH = Tg – Te SH: Evaporator outlet superheated degree
Tg: Suction pipe temperature detected by
heat exchanger gas pipe thermistor R8T,
R9T
Te: Low pressure equivalent saturated
temperature
SH = Tsh – Tm SH: Evaporator outlet superheated degree
Tsh: Suction pipe temperature detected by
the subcooling heat exchanger outlet
thermistor R5T
Tm: Low or middle pressure equivalent
saturated temperature