Electronic Expansion Valve Control; Hot Start Control (In Heating Operation Only) - Daikin VRVIII-S Service Manual

Outline of Control (Indoor Unit)
6.6

Electronic Expansion Valve Control

• Electronic expansion Valve Control

In cooling, to maximize the capacity of indoor unit heat exchanger (evaporator), operate the
electronic expansion valve under PI control so that the evaporator outlet superheated degree
(SH) will become constant.
In heating, to maximize the capacity of indoor unit heat exchanger (condenser), operate the
electronic expansion valve under PI control so that the evaporator outlet superheated degree
(Condenser outlet subcooled degree) will become constant.
Furthermore, the default value of the optimal evaporator outlet superheated degree (condenser
outlet subcooled degree) is 5 deg. However, this default value varies with the operating
performance.
6.7

Hot Start Control (In Heating Operation Only)

At startup with thermostat ON or after the completion of defrosting in heating operation, the
indoor unit fan is controlled to prevent cold air from blasting out and ensure startup capacity.
[Detail of operation]
When either the start condition 1 or the start condition 2 is established, the operations shown
below will be conducted.
64
Cooling SH=TH -TH
2 1
(Heating SC=TC-TH )
1
Defrost ending or oil return ending
or Thermostat ON
Hot start control
H/L remote
control setting
LL
OFF
Remote control
setting
Po (Horizontal)
SH : Evaporator outlet superheated degree
TH : Temperature (°C) detected with the liquid thermistor
1
TH : Temperature (°C) detected with the gas thermistor
2
SC : Condenser outlet subcooled degree
TC : High pressure equivalent saturated temperature
Hot start in progress
The fan is not OFF before initiating the hot start: LL
The fan is OFF before initiating the hot start: OFF
TH : Temperature (°C) detected with the gas thermistor
2
TC : High pressure equivalent saturated temperature
SiENBE34-703
Hot start ending conditions
·
lapse of 3 minutes
·
OR
[TH2]>34°C
·
"Tc">52°C
Normal control
Normal control
Function