Exhaust fans

Propeller Fan Type CBH

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. American Coolair has models with blade diameters from 7" to N4". 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.

Power Roof Ventilators (PRVs) 
Power roof ventilators of the type manufactured by American Coolair 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.

     American Coolair'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.

Hooded PRV -- Type PE

     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.