Daikin CTXU25G2V1B Service Manual page 42

SiBE12-908
3.12.1 Fully Closing with Power On
Initialize the electronic expansion valve when turning on the power, set the opening position and
develop pressure equalizing.
3.12.2 Pressure Equalization Control
When the compressor is stopped, open and close the electronic expansion valve and develop
pressure equalization.
3.12.3 Opening Limit
Outline Limit a maximum and minimum opening of the electronic expansion valve in the operating room.
Detail
The electronic expansion valve is fully closed in the room where cooling is stopped and is
opened with fixed opening during defrosting.
3.12.4 Gas Pipe Isothermal Control During Cooling
When the units are operating in multiple rooms, detect the gas piping temperature and correct
the electronic expansion valve opening so that the temperature of the gas pipe in each room
becomes identical.
3.12.5 SC Control
Outline 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.
Detail Start Functioning Conditions
After finishing the open control (630 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.
3.12.6 Starting Operation
Control the electronic expansion valve opening when the system is starting or the operating
room is changed, and prevent the system to be super heated or moistened.
3.12.7 Disconnection of the
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.
Function and Control
A maximum electronic expansion valve opening in the operating room : 450 pulses
A minimum electronic expansion valve opening in the operating room : 60 pulses
When the gas pipe temperature > the average gas pipe temperature → open the electronic
expansion valve in that room
When the gas pipe temperature < the average gas pipe temperature → close the electronic
expansion valve in that room
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.
/ Changing Operating Room Control
Discharge Pipe Thermistor
Control Specification
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