An HVAC system provides heating and/or cooling in industrial, commercial or residential buildings. HVAC stands for heating, ventilating and air conditioning. Another possible purpose is to circulate fresh air from the outside to dilute contaminants that gather inside from the use of chemicals.
Air conditioners dehumidify and cool air as it goes across a chilled coil surface. Inside the building, the coil serves as an air-to-liquid heat exchanger, sending liquid through the coil in tubes. These tubes feature finned surfaces that enlarge the surface area of the cold area, facilitating more widespread heat transfer. Either a refrigerant or chilled water can be the liquid inside the system. If using chilled water, the system has freeze protection when the water nears the freezing point.
A variety of different HVAC systems are available, depending on the needs of the space and the budget of the owner. A split system features an indoor air handler and an outdoor condenser, and is common in residential units or smaller commercial facilities. These have the highest rating for energy efficiency. A packaged unit contains both parts, but is all housed outside the building. For systems in which the owners do not want to install a central system, window units provide heating and air conditioning in the rooms to which they attach.