Daikin FTKE25BVM, Service Manual

Page: 112 / 298

Si12-411A Control Specification
Function and Control 101
3.12.8 Target Discharge Pipe Temperature Control
Obtain the target discharge pipe temperature from the indoor and outdoor heat exchange
temperature, and adjust the electronic expansion valve opening so that the actual discharge
pipe temperature become close to that temperature. (Indirect SH control using the discharge
pipe temperature)
Determine a correction value of the electronic expansion valve compensation and drive it
according to the deflection of the target discharge temperature and actual discharge
temperature, and the discharge temperature variation by the 20 sec.
3.12.9 SC Control
Outline Heat Pump Only
Detect the temperature of liquid pipe and heat exchanger of the rooms and compensate the
electronic expansion valve opening so that the SC of each room becomes the target SC.
„
When the actual SC is > target SC, open the electronic expansion valve of the room.
„
When the actual SC is < target SC, close the electronic expansion valve of the room.
Detail Start Functioning Conditions
After finishing the open control (660 seconds after the beginning of the operation), control all the
electronic expansion valve in the operating room.
Determine Electronic Expansion Valve Opening
Adjust the electronic expansion valve so that the temperature difference between the maximum
heat exchanger temperature of connected room and the temperature of liquid pipe thermistor
becomes constant.
3.12.10 Disconnection of the Discharge Pipe Thermistor
Outline Detect a disconnected discharge pipe thermistor by comparing the discharge pipe temperature
with the condensation temperature. If any is disconnected, open the electronic expansion valve
according to the outdoor air temperature and the operating frequency and operate for a
specified time, and then stop.
After 3 minutes of waiting, restart the unit and check if any is disconnected. If any is
disconnected stop the system after operating for a specified time. If the disconnection is
detected 4 times in succession, then the system will be down.
Detail Detect Disconnection
If a 630-second timer for open control becomes over, and a 9-minute timer for the compressor
operation continuation is not counting time, the following adjustment must be made.
1. When the operation mode is cooling
When the discharge pipe temperature is lower than the outdoor heat exchanger
temperature, the discharge pipe thermistor disconnection must be ascertained.
2. When the operation mode is heating (only for heat pump model)
When the discharge pipe temperature is lower than the max temperature of operating room
heat exchanger, the discharge pipe thermistor disconnection must be ascertained.
Adjustment when the thermistor is disconnected
When compressor stop repeats specified time, the system should be down.