A fan coil unit (FCU) is a device that uses a coil and a fan to heat or cool a room without connecting to ductwork. Indoor air is drawn over the coil, which heats or cools the air before being released back out into the room. As part of an HVAC system found in residential, commercial and industrial buildings, an FCU unit has simplistic design that is connected to ductwork and has a thermostat to regulate the temperature of a space. The thermostat controls the fan speed and/or the throughput of water to the heat exchanger using a control valve. FCUs control the temperature through the use of circulated cold or hot water that is taken from a centralised system equipment such as cooling towers and boilers.

These units with simplistic designs are more economical to install over other ducted options. Various configurations are available including horizontal (ceiling mounted) or vertical (floor mounted) designs