SiAU18-715 BP Unit ControlFunction 996.3 SH Control in Cooling OperationPurpose of theFunctionThis function ensures appropriate refrigerant distribution when many room units are operating inthe cooling mode.Outline The heat exchanger temperatures and gas pipe temperatures of operating room units aredetected by the gas pipe thermistors, and the electronic expansion valves' flow rates arecorrected so as to adjust the difference between heat exchanger temperature and gas pipetemperature of each room unit (hereafter referred to as SH) close to the target values.When SH is higher than target value → Opens the valve of that room unitWhen SH is lower than target value → Closes the valve of that room unitWhen the liquid pipe temperature is lower than the heat exchanger temperature, the electronicexpansion valve is opened more than normal opening.(Protection function to prevent rotor dew condensation)The gas pipe temperature and indoor heat exchanger temperature are detected at the time ofevery sampling time of 40 sec for the cooling SH control.In order to prevent dew condensation in connection pipe, gas pipe lower-limit temperature is setas follows.Outdoor Temperature Gas Pipe Lower-Limit Temperature-5 -220 -175 -1210 -615 -120 425 830 835 840 845 8024681012-20 0 20 40 60Outdoor air temperatureGas pipe lower-limit temperature(Q0378)Gas pipe lower-limit temperature = × DOA - 17 (however 8ºC or lower)DOA:Outdoor air temperature240256
