A fan coil unit (FCU) is a type of heating and cooling system used in commercial and residential buildings. It is made up of a fan, a coil, and a set of controls. The fan draws air from the room and passes it over the coil, which is filled with a refrigerant. The refrigerant absorbs heat from the air, cooling it down. The cooled air is then circulated back into the room. The fan and coil are connected to a set of controls, which allow the user to adjust the temperature and fan speed. FCUs are typically installed in the ceiling or wall, and are relatively quiet and energy efficient. They are often used in conjunction with other heating and cooling systems, such as air conditioners and furnaces. FCU manufacturers provide a wide range of products, from basic models to more advanced units with additional features. They are a popular choice for many commercial and residential buildings, as they provide efficient and reliable climate control.