There are some advantages and dis-advantages direct drive and belt drive exhaust fans and supply fans have over each other. Either of these motor mount options can typically be found in wall mount exhaust and supply fans, roof mount exhaust and supply fans, inline duct fans and air circulation products. Our goal with this post is to cover some of the main differences, advantages and dis-advantages between the two and help you make a more educated decision for your specific application.
Direct Drive Advantages
Direct Drive fans are typically lower maintenance since there are no bearings, belts or sheaves to maintain. Because of the fewer parts involved, they can often be more compact in design. Direct drive fans typically work better when you are trying to vary the speed of the fan with a VFD (Variable Frequency Drive) or a Potentiometer (Rheostat – Variable Speed Controller).
Direct Drive Dis-Advantages
Direct drive fans typically have less performance flexibility because you are limited to the RPM of the motor unless you use some sort of speed control device. It may be more difficult to access the motor because the propeller is mounted directly to the motor shaft. There are typically fewer motor options on direct dive fans because larger propellers may require slower motor speed (rpm) or revolutions per minute. And when you lower the motor speed the motors are often bigger, cost more money and less available. The motors are exposed to the air stream, so the maximum air stream temperature is limited to what the motor can handle. And, when dealing with contaminated air streams such as abrasive or corrosive air streams, the motor tpe may need to be Totally Enclosed Fan Cooled instead of ODP (Open Drip Proof Motors).
Belt Drive Advantages
Belt drive fans have greater performance flexibility because you can use the drive package to adjust the fan speed as needed. This is important when trying to balance the ventilation system. Motor access is easier and the fan may be less difficult to work on. Because the motor is typically out of the air stream, this may be a better fit for high temperature and contaminated air applications. There may be even less stress on the motor if the propeller were to come out of balance over time because of wear or contamination. The adjustable motor pulleys typically used on the motor will allow you to adjust performance by 10-15%.Belt Drive Fan Dis-Advantage
Belt Drive Dis-Advantages
Belt drive fans are more maintenance because you have to lubricate the bearings, maintain proper belt tension and replace the belt over time. Belt drive fans can take up more space and cost more money because of the increase in moving parts and components.