Sc Control In Heating Operation; Heat Exchanger Isothermal Control In Heating Operation - Daikin RMXS-L Series Service Manual

Branch Provider (BP) Unit Control
6.4

SC Control in Heating Operation

Outline This function ensures appropriate refrigerant distribution when many indoor units are operating in
heating operation.
Details The heat exchanger temperatures and liquid pipe temperatures of operating indoor units are
detected by the liquid pipe thermistors, and the flow rates of the electronic expansion valve are
corrected so as to adjust the difference between the heat exchanger temperature and liquid pipe
temperature of each indoor unit (hereafter referred to as SC) close to the target values.
When SC is higher than target value → Opens the valve of that indoor unit
When SC is lower than target value → Closes the valve of that indoor unit
The liquid pipe temperature and indoor heat exchanger temperature are detected with a sampling
time of 20 seconds for the heating SC control.
6.5

Heat Exchanger Isothermal Control in Heating Operation

Outline This function ensures appropriate refrigerant distribution when indoor units are operating in heating
operation.
It prevents abnormal increase of the high pressure and operation with gas shortage due to uneven
refrigerant distribution (Protection function).
Details The indoor heat exchanger thermistors (of all connected indoor units to the same BP unit including
non-operating indoor units) in heating operation are detected. Then, the highest heat exchanger
temperature is compared with the heat exchanger temperature of each indoor unit. If the
temperature difference exceeds the predetermined value, it is judged that the indoor heat
exchanger thermistor position is in subcooled zone, and the electronic expansion valves of indoor
units with the temperature difference exceeding the predetermined level are opened to return to the
saturation zone.
Since this is a protection function, it is effective for all connected indoor units in heating operation
excluding those in defrosting operation. This function is inactive in indoor units with transmission
problems.
The heat exchanger temperature is detected with a sampling time of 20 seconds of the heat
exchanger isothermal control, and maximum value of each heat exchanger temperature is
obtained.
If the temperature difference between the heat exchanger temperature and maximum heat
exchanger temperature value exceeds 8°C (14.4°F), it is judged that the heat exchanger
intermediate is in the subcooled zone, and the electronic expansion valve is opened.
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SiUS181631EA
Functions and Control