Daikin VRV II RXYQ5MY1B Service Manual page 121

Outline of Control (Indoor Unit)
6.5.2 Discharge air temperature control
Used to control the EV (electronic expansion valve) opening and thermostat ON/OFF so as to
keep the discharge air temperature at the set temperature.
(1) Cooling operations
Discharge
air
T4
EV
T1: Temperature detected by suction air thermistor Th1
T2: Temperature detected by liquid pipe temp. thermistor Th2
T3: Temperature detected by gas pipe temp. thermistor Th3
T4: Temperature detected by discharge air thermistor Th4
EV: Electronic expansion valve opening
If the discharge temperature
T4 is higher than the discharge
setting temperature Ts
No
Is EV possible
Judge if the superheat degree
is not too small when the EV is
opened.
EV=EV+∆EV
110
T3
T2
SH=T3–T2
Yes
T4 > Ts?
to open?
Yes
If yes,
EV is opened.
CPU
T1
Calculate superheat degree.
No
EV possible to
close?
Yes
If yes,
EV is closed.
EV=EV–∆EV
SiE39-404
Refrigerant
Ts
Temp.
Setting
Refrigerant
If the discharge temperature T4
is lower than the discharge
setting temperature Ts
Is
No
Judge if the superheat degree
is not too large when the EV is
closed.
Function