Air Handling Unit

The Air Handling Unit is an appliance used to circulate and recondition air. The main function of the AHU is to take in outside air, recondition it, and return fresh air. It also has the feature of controlling the temperature of the environment.

An Air Handling Unit definition and uses

Air Handling Units, represented by AHU in project equipment specification tables, are integral parts of air supply systems with control over temperature and humidity for application in both cold and hot seasons. The Air Handling Unit (AHU) is an essential part of air conditioning systems and can be used in all climates. It is usually a large metal box containing a blower, heating or cooling elements, filter racks or chambers, sound attenuators, and dampers.

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• An Air Handling Unit AHU is often used to adjust temperature and humidity and supply conditioned air to halls, venues, hospitals, offices, and other large spaces and is superior to a fan coil system—in particular, in humid regions—as, besides the better quality of the output air, installing fan coil units requires laying an extensive network of supply, return, and drain pipes which are prone to rusting due to the moisture in the soil, whereas the ducts to supplement an AHU—that are often implemented in the drop ceiling—have a much longer service life.
• Generally speaking, an Air Handling Unit (AHU) mixes the return air from the building with fresh air, passing them through an initial aluminum filter. In the summer, the air is cooled by passing through the fins of a cooling coil (or a heat exchanger), whereas it is heated in the winter by running through hot water (or vapor) coil. The conditioned air is then directed to the rooms through the duct system. Further, when the need arises, the supply air can be humidified by water or vapor in the unit, before entering the cooling or heating coil and distribution via the duct system.
• Air handling units often consist of: The structure, the frame, the fan, the electric motor, air filters, cooling and heating coils, humidification nozzles, input, output, and return air dampers, and control equipment.

  

Air Handling Units (AHUs) benefit different environments

Air-handling units that directly use a refrigerant for cooling instead of cold water supplied by a chiller system are air-handling units with DX coil.

• Given the significance of air quality in certain places, such as the electronics industry, food industry, pharmaceutical industry, operating rooms, hospitals, and others, using hygienic air handling units is recommended for supplying sterile air. These units have special capabilities including noise-absorbing cabins (nickel-chromium alloy), coupling with an air recovery system, HEPA filters, and UV lamps.
• In hygienic air handling units, 100% of the fresh air passes through the wire mesh and bag filters—that absorb up to 95% of particulates—and then a HEPA filter absorbs small particulates with diameters down to 0.3 microns. Further, in a super-hygienic air handling unit, the input air enters a sterile environment after passing through a ULPA filter—that absorbs particulates as small as 0.12 microns—thus providing a high level of filtration.
• Given the important role of the coil in air handling units, when placing an order for a unit, note the number of rows, thermal surface area, and the number of fins per square inch of heating and cooling coils, as well as the diameter and thickness of the coil, and the frame and its constituting sheets. For further information on the selection of an air handling unit, contact our specialists at DamaTajhiz.
• Whether the unit comes with a humidification system. In colder climates where continuous heating will make the air drier humidification is often necessary, avoiding uncomfortable air quality and increased static electricity.

Temperature control in air handling units three methods

First Method

An electrical or motorized three-way valve is fixed on the supply or return pipe of chilled/heated water coil as in switched on/off by a thermostat fixed in the return duct. Chilled/heated water flow is switched on/off or regulated to adjust the temperature of the environment.

Second Method

The speed of the motor and fan of the air handling unit (AHU) is adjusted by a thermostat installed in the room or the hallway or other suitable places (similar to the case with fan coil units). The control system must be designed to allow the duct thermostat and three-way valve to operate first and then, if necessary, let the room thermostat control the fan speed.

Third Method

Controlling the AHU capacity by a motor-driven, fresh input and return air damper that determines the mixing ratio of fresh and return air.

they are installing a flow switch on the evaporator output path (chilled water) to the cooling coil of the heat exchange equipment (including fan coil and air handling units) for commanding the chiller to stop when circulator pumps in the refrigeration circuit shut down.

When installing the Air Handling Unit (AHU) note that

• Large-scale units are difficult to transport due to their dimensions, as a result, they are transported in separate parts and then assembled during installation.
• Air handling units that are made of galvanized steel sheets can have either a horizontal or vertical configuration depending on the installation conditions. Air handling units are designed and produced in single-zone and multi-zone models. In the single-zone type, all parts of the building that are covered by the AHU are supplied with air at the same temperature and humidity, whereas multi-zone models draw on special dampers to provide air under different temperature and humidity conditions.
• The specifications of the foundation atop which the Air Handling Unit (AHU) sits depend on the structural conditions of the project and the weight and dimensions of the equipment.
• According to engineering standards, after installation, a space as large as 1.5 times the width of the equipment must remain empty on one side to allow for the replacement of the coils when the need arises during the long service time of the unit.
• It is necessary to place a drain in the Air Handling Unit (AHU) room for periodic cleaning and maintenance.
• To improve and maintain the efficiency of the unit, it is important to properly insulate the equipment, in particular, the ducts running outdoors that are exposed to sunlight or cold air.

You can also read the article BENEFITS OF AIR HANDLING UNITS IN BUILDINGS for more information.

Final speech

The specialized collection (Damatajhiz) (the first and most reliable authority in the country in the field of building facilities equipment and all air conditioning devices), offers you all kinds of sand filters and hundreds of other products, guaranteeing the originality of the product, valid warranty, and reasonable price. In addition, if you have any questions about choosing and comparing the brands of this product, you can get free advice from the heating equipment experts.

In Iran, the first and most famous specialized group in the field of building installation equipment, air conditioners, and all equipment for swimming pools, saunas, and jacuzzis since 2004, DamaTajhiz is a specialized group. Refer to the time of this group. For more information, you can get advice from the DamaTajhiz Engineering and Production Company experts by calling 021-88822550.

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