Daikin REYQ-AATJA, Service Manual, Page: 142 / 495

Basic Control SiUS372201EA
135 Part 4 Functions and Control
5.4 Electronic Expansion Valve PI Control
Main electronic expansion valve EVM control
When the outdoor unit heat exchanging is performed via the condenser (Y7S, Y9S or Y10S is set to
OFF), this function is used to exert PI control on the electronic expansion valve (Y1E, Y2E or Y5E)
so that the condenser outlet subcooling degree (SC) will become constant.
When the outdoor unit heat exchanging is performed via the evaporator (Y7S, Y9S or Y10S is set
to ON), this function is used to exert PI control on the electronic expansion valve (Y1E, Y2E or Y5E)
so that the evaporator outlet superheating 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 (Y3E) so that the evaporator-side gas pipe
superheating degree (SH) will become constant.
SC = Tc – Tf SC:
Tc:
Tf:
Condenser outlet subcooling degree
High pressure equivalent saturated temperature
Liquid pipe temperature detected by heat exchanger liquid pipe
thermistor R6T, R7T, R22T
SH = Tg – Te SH:
Tg:
Te:
Evaporator outlet superheating degree
Suction pipe temperature detected by heat exchanger gas pipe
thermistor R2T, R9T, R21T
Low pressure equivalent saturated temperature
SH = Tsh – Tm SH:
Tsh:
Tm:
Evaporator outlet superheating degree
Suction pipe temperature detected by the subcooling heat
exchanger outlet thermistor R12T
Low or middle pressure equivalent saturated temperature