Patent ID: 6874334

Claim:
An air conditioning system comprising: an outdoor unit having a compressor and an outdoor heat exchanger; an indoor unit installed in a ceiling, the indoor unit comprising: an indoor heat exchanger defining a space therein in communication with a room; a fan in the space that draws air in and that discharges air to the room through the indoor heat exchanger; and a ventilation guide duct on an underside of the indoor heat exchanger, the ventilation guide duct guiding external air to the room through the fan and room air from the room; an air supply duct and an air discharge duct each having one end connected to the ventilation guide duct for guiding the external air to the room and the room air from the room, respectively; and a preheat exchanger provided between the air supply duct and the air discharge duct, the preheat exchanger indirectly exchanging heat between external air and room air passing through the air supply duct and the air discharge duct.