What is a head unit (fan coil)?
A head unit is the indoor component of a split-system air conditioner, mounted on a wall or bulkhead, that receives refrigerated or heated air from the outdoor compressor and distributes it throughout a room via a fan.
The head unit, also called a fan coil or indoor unit, is the visible half of a split system that sits inside your home or business. It mounts directly on an internal wall or into a ceiling bulkhead and connects to the outdoor compressor via refrigerant lines run through your walls.
Inside the head unit, a fan draws warm or cool air across an evaporator coil containing refrigerant. This process either removes heat from the room (cooling mode) or releases stored heat back into the air (heating mode). The conditioned air then flows out through vents into the space, keeping it at your set temperature. Most models operate quietly and include a thermostat control, either built into the unit or wall-mounted nearby.
Head units vary in shape and capacity. Wall-mounted units are common in individual rooms or apartments, while bulkhead or ceiling-mounted cassettes suit open-plan areas. The size and output rating must match the volume and insulation of the space it serves, which is why proper installation assessment matters. Without an adequately sized head unit, you get poor air distribution, high energy use, or uneven comfort.
The indoor unit is separate from the outdoor condenser, which is why the system is called "split." This separation lets installers place the noisy compressor outside while keeping bedrooms and living areas quiet.