HVAC Licensing Study Guide by Rex Miller

Author:Rex Miller
Language: eng
Format: epub
Publisher: McGraw-Hill Education
Published: 2018-07-15T16:00:00+00:00

Applications for Fans

The numerous applications of fans in the field of air conditioning and ventilation are well known, particularly to engineers and air-conditioning repair and maintenance personnel. The various fan applications are as follows:

• Attic fans

• Circulating fans

• Cooling-tower fans

• Exhaust fans

• Kitchen fans

Exhaust fans are found in all types of applications, according to the American Society of Heating and Ventilating Engineers. Wall fans are predominantly of the propeller type because they operate against little or no resistance. They are listed in capacities from 1000 to 75,000 feet3/minute. They are sometimes incorporated in factory-built penthouses and roof caps or provided with matching automatic louvers. Hood exhaust fans involving duct work are predominantly centrifugal, especially in handling hot or corrosive fumes.

Spray-booth exhaust fans are frequently centrifugal, especially if built into self-contained booths. Tube axial fans lend themselves particularly well to this application where the ease of cleaning and suspension in a section of ductwork is advantageous. For such applications, built-in cleanout doors are desirable.

Circulating fans are invariably propeller or disk-type units and are made in a vast variety of blade shapes and arrangements. They are designed for appearance as well as utility. Cooling-tower fans are predominantly of the propeller type. However, axial types are also used for packed towers, and occasionally a centrifugal fan is used to supply draft. Kitchen fans for domestic use are small propeller fans arranged for window or wall mounting and with various useful fixtures. They are listed in capacity ranges of from 300 to 800 feet3/minute.

Attic fans are used during the summer to draw large volumes of outside air through the house or building whenever the outside temperature is lower than that of the inside. It is in this manner that the relatively cool evening or night air is utilized to cool the interior in one or several rooms, depending on the location of the air-cooling unit. It should be clearly understood, however, that the attic fan is not strictly a piece of air-conditioning equipment because it only moves air and does not cool, clean, or dehumidify. Attic fans are used primarily because of their low cost and economy of operation, combined with their ability to produce comfort cooling by circulating air rather than conditioning it.

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