What is an Air Handler?

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  • Written By: B. Turner
  • Edited By: Bronwyn Harris
  • Last Modified Date: 04 November 2019
  • Copyright Protected:
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An air handler is a mechanical device used to distribute air throughout a home or building. It is used in conjunction with a heat pump or air conditioning system, and may be installed indoors or outside the home depending on the model. The term “air handler unit" (AHU) is often used to described this device.

The cooling process begins when fresh air from outside is fed into the air handler. A refrigerant or coolant in the handler cools this fresh air, then blowers or fans send it into the building's ductwork. The ducts distribute this cool air to each room. A second set of ductwork, known as “return ducts” collect warm exhaust air and transfer it back to the air handler.

Once the warm air reaches the air handling unit, the refrigerant in the unit collects the heat from the air and sends it to an outdoor compressor. The heat is expelled to the outside, and the refrigerant is sent back to the air handler to cool more air and repeat the cooling cycle. These systems work in reverse during the winter to heat the air in the home.

An air handler is typically installed on either the rooftop on in an indoor mechanical room. In general, these devices are located outdoors in a commercial application, and indoors in most residential settings. Special support pads made of concrete are often used to support them, and additional supports may be added to minimize noise and vibration.


When choosing air handlers, it's important to match the unit to the outdoor compressor. Some compressors are designed to only work with specific air handling components, while others are more versatile. Buyers should also be aware of energy efficiency ratings, noise levels and control systems for each type of air handler.

The size of an air handler is also a major issue when making a purchase. Buyers must choose a unit with the appropriate cooling capacity for the space or building, and must also find a unit that will fit in the available installation space. A unit with too low of a cooling capacity may leave the building feeling too warm, while one that is too large can lead to higher utility costs and wasted energy.

As with most heating and cooling components, an air handler must be properly maintained to function at its peak level of performance. Maintenance personnel should check and replace the filter in the unit in accordance with the manufacturer's recommendations. The system should also be installed and programmed by a skilled installer to maximize performance and reduce the risk of operational issues.



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