A design fan coil is a type of heating and cooling system that is commonly used in residential and commercial buildings. It consists of a fan, a coil, and a heat exchanger. The fan is used to circulate air throughout the building, while the coil is used to heat or cool the air as it passes through. The heat exchanger is used to transfer heat from one medium to another, such as from air to water. Design fan coils are a cost-effective way to heat and cool a building, as they are energy efficient and require minimal maintenance. They are also quieter than other types of heating and cooling systems, making them a popular choice for many homeowners and businesses.