Split systems consist of the external and internal units (one or several) which are connected by copper tube with coolant. The operation principle is similar to work of ordinary refrigerator. The coolant circulates through the evaporator, located in the internal unit, where evaporation takes away heat from internal air. Then, reaching the temperature of internal air, activates the compressor (at compression its temperature grows) and pumps to the external unit, where it is cooled in the condenser with external air; then the cooled refrigerant pumps to the internal unit again.
Modern split system are equipped with additional functions: air purifiers/cleaners, humidity controls, and ionizers. Many can be controlled by remote control or “smart “ thermostat. These systems can also accommodate both cooling and heating.