How To Ventilate Buildings

By Author: Oleg Tchetchel
Total Articles: 50
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Power roof fans of the type manufactured by CB Fan Co. are very similar in basic design to the wall fans. Size and capacity closely parallel the wall fans. One of the most popular PRVs is the upblast exhauster. This unit utilizes air velocity to expel rain or snow that may try to penetrate into the structure. When the unit is not in service, butterfly dampers effectively seal the opening against the weather. Because of the straight through air flow design, this is the most effective and efficient PRV available. CB Fan Co.'s hooded PRV design is similar to the upblast PRV. Instead of butterfly dampers, a stationary hood shields the unit from rain and snow. A backdraft damper prevents air infiltration when unit is not in use. The hood offers some resistance to air flow. For this reason, the upblast PRV is more efficient and economical. PRVs are specified by many design engineers because they are roof located and away from operations within the structure. Maintenance and service can be performed from a roof location. Cost per CFM may exceed by a small margin that of wall fans with equal capacity. However, the advantages may ...
... more than offset the slight disadvantage of unit cost.

One of the "work horses" of many ventilation and cooling systems is the wall-mounted exhaust fan. A mounting panel attaches the fan to the inside face of a wall opening. An automatic or motor-operated wall shutter is mounted on the outside face of the wall to provide weather protection when the fan is not in operation. These wall exhausters are available in a wide range of sizes and capacities. CB Fan Co. has models with blade diameters from 7" to 84". Capacity ranges from 250 cubic feet per minute (CFM) to approximately 100,000 CFM from a single fan. Fans of this type are quite efficient, dependable and require relatively little maintenance. Minor disadvantages may relate to their wall location. This location may result in interference with operations of the building, may cause damage to the fan itself or it may be a possible disturbance to personnel working in the proximity of the fan.

Supply fans may be either wall mounted or roof mounted. Most Buffalo fans and PRVs of the type described above are available for supply usage. Additional modifications and special products are available from CB Fan Co. to tailor their usage to individual installations. For example, filters may be added to supply PRVs when desirable. Also, American Coolair's uniquely designed Model PT Power Tube Fan can be used to supply make-up air, in summer and winter, without the need for the supplemental heating required by most other make-up air systems.

Many breeze conditioning systems are designed without the use of supply fans or make-up air units of any kind. The exhaust system creates a slight negative pressure in the building and outside air is induced through openings designed for this purpose. Intake louvers are usually mounted at the opposite end of the building from the exhaust fans in suitable wall locations. When the breeze conditioning system is in use, the louvers are opened manually or by damper motors; when not in use, the louvers are closed to provide weather protection. An alternative method for providing air intake openings is through the use of roof mounted hooded supply vents. American Coolair's Type PE PRV can be furnished without a fan for this purpose.

Many buildings are much too large to rely on the circulation of air at the proper velocity and direction without the use of supplemental fans. In other cases, a system of exhaust and supply fans may be lacking in the building. Air circulators or booster fans can usually solve the problem CB Fan Co. customers have used our Type UD propeller fans (7" to 24") and CABL/CABH propeller fen (24" to 54" ) to good advantage for this purpose. Pedestal fans have been used as air circulators in some cases. Spot coolers or "man coolers" are air circulators used for a specific purpose or problem area. Air circulators have the big advantage of being readily available, inexpensive and easy to install. They are not a satisfactory substitute for a complete ventilation and cooling system, however.

In some sophisticated systems, elaborate duct work and diffusers are incorporated for distribution of air throughout a building. This type of system is expensive and most ABuffalo Fan Breeze Conditioning Systems avoid this degree of sophistication. Instead, simple, inexpensive baffles, deflectors and diffusers are used to good advantage. These items are usually fabricated and. installed at the job. They are made from a variety of inexpensive materials including polyethylene, masonite, plywood and sheet metal. Specific applications of these items will be discussed in subsequent sections.

Additional information can be found at the CB Blower company web site http://cbblower.com

Oleg Chechel
Industrial Equipment Engineer
olegsystems@olegsystems.com
CB Fan Co.
http://www.cbblower.com/index.html
http://www.cbblower.com/fanblowerinquiry.html