Air handler
Encyclopedia : A : AI : AIR : Air handler
An air handler (Air Handling Unit - in the UK) is a device used as part of an HVAC (Heating, Ventilating, and Air Conditioning) system. Usually, an air handler is a large unit containing a blower, heating and/or cooling elements, filter racks or chambers, sound attenuators and dampers, but not including the ductwork through the building.
Air handlers usually contain large squirrel cage blower driven by an induction electric motor. The blower may operate at a single speed, offer a variety of pre-set speeds, or be driven by a Variable Frequency Drive so as to allow a wide range of speeds. Some residential systems use a brushless DC electric motor, which contains internal drive equipment that allows the blower to automatically compensate for static pressure and operate much more efficiently than is possible with a blower powered by an induction motor, even a multi-speed one. Additionally, variable pitch fans can be used to alter the air flowrate.
If used to supply heat, the air handler may contain a fuel-burning heater or it may simply contain coils that are heated using circulating water or steam with the heat provided by a central boiler.
If used for cooling, the unit may contain a refrigeration system or simply a coil cooled by building chilled water provided by a chiller unit or a direct refrigerent coil within the unit.
Air filtration may be mechanical, HEPA, electrostatic, or a combination of techniques may be used.
Humidification may be provided. Air handlers commonly also provide provisions to allow the introduction of fresh air into and the exhausting of stale air from the building. An air-to-air heat exchanger may be fitted for this purpose in higher-efficiency units.
Control may be as simple as an off/on thermostat or as compex as a building automation system using BACnet or LonWorks.
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