Small air handlers, for local use, are called terminal units, and may only include an air filter, coil, and blower; these simple terminal units are called blower coils or fan coil units.
A Fan Coil Unit (FCU) is a simple device consisting of a heating and or cooling heat exchanger or ‘coil’ and fan. It is part of an HVAC system found in residential, commercial, and industrial buildings. A fan coil unit is a diverse device sometimes using ductwork, and is used to control the temperature in the space where it is installed, or serve multiple spaces. It is controlled either by a manual on/off switch or by thermostat, this in turn controls the throughput of water to the heat exchanger using a control valve and/or the fan speed.
Due to their simplicity and flexibility fan coil units can be more economical to install than ducted 100% fresh air systems (VAV) or central heating systems with air handling units or chilled beams. Unit configurations are numerous including horizontal (ceiling mounted) or vertical (floor mounted).