ABSTRACT
Fans are designated by type, class, fan rotation, drive arrangement, motor location, air discharge direction, and, for centrifugal fans, width of fan wheel. Heating, ventilating and air conditioning (HVAC) fans are divided into three general categories: centrifugal fans, axial fans, and special design fans such as tubular centrifugal fans, centrifugal power roof ventilators, and axial power roof ventilators. The forward curved fan is sometimes called a squirrel cage fan. It is used in low to medium pressure applications such as residences and in package units because it is quieter than the higher speed, higher pressure fans. Fan discharge is always viewed from the drive side with the fan sitting on the ground. Tubular centrifugal fans are “non-overloading” fans. If a motor is selected to handle the maximum brake horsepower shown on the performance curve, it will not be overloaded in any condition of fan operation.
