How many heat transfer coils do conventional air-cooled central air conditioning systems have?

Conventional air-cooled central air conditioning systems typically have two heat transfer coils: an evaporator coil and a condenser coil. The evaporator coil is located inside the air handler or furnace, where it absorbs heat from the indoor air, allowing the refrigerant to convert into gas and thus cool the air. The condenser coil is located outside, where the refrigerant releases the absorbed heat to the outdoor air, transitioning back into a liquid state. This dual-coil system is necessary for the efficient operation of the air conditioning unit, as each coil serves a distinct purpose in the cooling process, facilitating the transfer of heat between the indoor and outdoor environments. This configuration is critical for maintaining indoor comfort during hot weather.