Air conditioning system using heat pump and air heating device

An air conditioning system comprising:

• a heat pump provided to heat or cool a circulating refrigerant;
• an air heating device provided to burn a fuel so as to heat circulating water so that air is heated by the heated water;
• a furnace case provided with the air heating device;
• an intermediate heat exchanger disposed outside the furnace case and provided to exchange heat between the refrigerant and the water,
• a water heating flow control valve disposed in the water heating passage to control a flow rate of the water flowing in the water heating passage, and
• a processor electrically connected to the heat pump and the air heating device,
• wherein the air heating device comprises:
• a water heater provided to receive heat from a combustion gas generated by combustion reaction so as to heat the water;
• an air heat exchanger provided to receive the water heated by the water heater so as to exchange heat with the air to be discharged for the heating;
• and
• a furnace main passage provided to circulate the water,
• wherein the furnace main passage comprises:
• a furnace passage passing through the air heat exchanger;
• a water heating passage branched from one end of the furnace passage to pass through the water heater;
• and
• an intermediate heat exchange passage provided with an intermediate heat exchange inflow passage branched from one end of the furnace passage and connected to the intermediate heat exchanger and an intermediate heat exchange discharge passage having one end connected to the intermediate heat exchanger, and
• wherein the processor is configured to control the water heating flow control valve so that a flow rate of the water flowing in the intermediate heat exchange passage is less than that of the water flowing in the water heating passage when a defrost mode, in which the heat pump operates for the cooling, and the air heating device operates for the heating, is finished.