What is the definition of a vav fan powered boxes? It is a type of HVAC system designed to provide both heating and cooling to buildings. VAV fan powered boxes use the existing air system, but the fan is powered by an external source instead of the furnace or air conditioner. This type of system is used to regulate the temperature of individual rooms or zones within a building. The fan is powered by either electricity or gas and is connected to a control box that regulates the speed of the fan based on the temperature of the space it is serving. The fan pulls air from the return duct, mixes it with heated or cooled air from the heating or cooling source, and then distributes the air to each room or zone. VAV fan powered boxes can be used to effectively regulate the temperature within a building, ensuring a comfortable environment for everyone. They are also more energy efficient than traditional heating and cooling systems, making them an ideal solution for many commercial and residential buildings.