Sc Control In Heating Operation; Heat Exchanger Isothermal Control In Heating Operation - Daikin Super Multi Plus E-Series FTXG25EV1BW Service Manual

SiBE18-821_C
Note: 1. In SkyAir models, the indoor units are equipped with distribution capillary tubes; therefore,
2. In SkyAir models, the heat exchanger intermediate position is provided on the liquid
6.4

SC Control in Heating Operation

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

Heat Exchanger Isothermal Control in Heating Operation

Purpose This function ensures appropriate refrigerant distribution when room units are operating in the
heating mode.
It prevents abnormal increase of the high pressure and operation with gas shortage due to
uneven refrigerant distribution (Protection function).
Outline The indoor unit heat exchanger thermistors (of all connected indoor units to the same BP unit
including non-operating room units) in heating operation are detected. Then, the highest heat
exchanger temperature is compared with the heat exchanger temperature of each room unit. If
the temperature difference exceeds the predetermined value, it is judged that indoor unit heat
exchanger thermistor position in subcooled zone, and the electronic expansion valves of room
units with the temperature difference exceeding the predetermined level is opened to return to
the saturation zone.
Since this is a protection function, it is effective for all connected room units in heating operation
excluding those in defrosting operation. This function is inactive in room units with transmission
problems.
Detail The heat exchanger temperature is detected at every sampling time of 20 second 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, it is judged that the heat exchanger intermediate is
in the subcooled zone, and the electronic expansion valve is opened.
Function
the heat exchangers may superheat even when the condition is met.
connection pipe side; as a result, superheated condition is difficult to detect.
BP Unit Control
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