Outline of Control (Indoor Unit) SiUS331604E63 Functions and Control6.8 Electronic Expansion Valve ControlElectronic expansion valves in indoor units have the functions of conducting superheated degree control incooling operation and subcooled degree control in heating operation. However, if the indoor units receive acontrol command such as a protection control command or a special control command from the outdoor unit, theunits will give priority to the control command.• Superheated degree control in cooling operationThis function is used to adjust the opening of the electronic expansion valve so that superheated degree (SH),which is calculated from the detection temperature (Tg) of the gas pipe thermistor (R3T) and the detectiontemperature (Tl) of the liquid temperature thermistor (R2T) of the indoor unit, will come close to a targetsuperheated degree (SHS).At that time, correction to the superheated degree is made according to the differences (∆T) between settemperature and suction air temperature.• Normally 5°C (9°F).• As ∆T (Remote controller set temp. – Suction air temp.) becomes larger, SHS becomes lower.• As ∆T (Remote controller set temp. – Suction air temp.) becomes lower, SHS becomes larger.• Subcooled degree control in heating operationThis function is used to adjust the opening of the electronic expansion valve so that the high pressure equivalentsaturated temperature (Tc), which is converted from the detected pressure of the high pressure sensor in theoutdoor unit, and the subcooled degree (SC), which is calculated from the detected temperature (Tl) of the liquidtemperature thermistor (R2T) in the indoor unit, will come close to the target subcooled degree (SCS).At that time, corrections to the subcooled degree are made according to differences (∆T) between settemperature and suction air temperatures.• Normally 5°C (9°F).• As ∆T (Remote controller set temp. – Suction air temp.) becomes larger, SCS becomes lower.• As ∆T (Remote controller set temp. – Suction air temp.) becomes lower, SCS becomes larger.SH = Tg – Tl SH: Evaporator outlet superheated degreeTg: Indoor unit gas pipe temperature (R3T)Tl: Indoor unit liquid pipe temperature (R2T)SHS (Target SH value) SHS: Target superheated degreeSC = Tc – Tl SC: Condenser outlet subcooled degreeTc: High pressure equivalent saturated temperaturedetected by the high pressure sensor (S1NPH)Tl: Indoor unit liquid pipe temperature (R2T)SCS (Target SC value) SCS: Target subcooled degree
