Subject to change of the number of operation (thermostat-on) units, capacity, air flow rate, suction temperature, of indoor units
? Load on total system changes.
? Loads on every indoor unit are different.
Compressor Capacity Control
In order to maintain the heating capacity against condenser capacity and load fluctuation, based on the pressure detected by high-pressure sensor control (Pc), compressor capacity is so controlled to put the high pressure equivalent saturation temperature (condensing temperature = Tc) close to target value.
Superheated Degree Control of Outdoor Electronic Expansion Valve
In order to maintain the superheated degree in evaporator, based on the pressure detected by the low pressure sensor (Te) and the temperature detected by the thermistor of suction pipe, outdoor electronic expansion valve is so controlled as to put superheated degree at evaporator outlet close to target value.
• Superheated degree SH = (outdoor suction pipe temperature – outdoor evaporating temperature)
Subcooled Degree Control of Indoor Electronic Expansion Valve
In order to distribute proper refrigerant flow rate in spite of different loads on every indoor unit, based on the pressure detected by the high pressure sensor of outdoor unit (Tc) and the temperature detected by the thermistor of indoor liquid pipes, indoor electronic expansion valve is so controlled as to put subcooled degree at condenser outlet close to target value.
• Subcooled degree SC = (outdoor condensing temperature – indoor liquid pipe
temperature)
