What Is the Difference Between a Blower & a Fan?

If you're comparing air conditioners, furnaces, appliances or certain electronic devices, you'll likely see the labels "blowers" and "fans" used in the product descriptions. There is a distinct difference between blowers and fans, and knowing that difference can help you choose the best product for your needs.

Airflow

The "specific ratio" of a fan or blower is the ratio of discharge pressure over suction pressure. In other words, it correlates to the amount of air the device is able to move. Fans have a ratio of up to 1.11, while blowers have ratios between 1.11 and 1.20). In short, blowers create more airflow than fans.

Size

Blowers are typically bigger. While they move more air, blowers are impractical for certain smaller items or airflow systems. Standard propeller blades are rare for blowers, and the units often use a larger and more complex centrifugal device.

Energy Efficiency

Depending on the fan or blower manufacturer, energy efficiency varies. A fan, however, usually consumes less energy than a blower.

Blower vs. Fan

People use blowers and fans for many different types of situations. Blowers, also known as centrifugal fans, are in automobile systems and home heating, ventilating and air-conditioning (HVAC) systems. Fans, also known as axial fans, are in automobile cooling systems and home ventilation systems. A typical window box fan is an example of an axial fan. Both types have advantages and disadvantages.

Airflow

Axial fans force airflow along the axis of the rotating shaft, which spins the fan. In an airplane, the propeller forces the air from the front of the plane to the back along the sides of the plane. Centrifugal fans pull air in along the axis, but forces it out perpendicular to the axis. If you look at a blower from a car's HVAC system, then you will see that the blower takes air in through the front and sends it out along the sides of the blower.

Power

Axial fans tend to require more power than centrifugal fans. Because these fans are designed for low-pressure, high-volume situations, they require more power to achieve the high rotational speed necessary for normal operation. When you need high efficiency, use centrifugal fans. Centrifugal fans can generate high pressures, but in a more efficient manner than axial fans. For this reason, centrifugal fans are the most used type of industrial fan.

Flexibility

Despite the advantages of a centrifugal fan over a axial fan, axial fans do have some disadvantages. The most important is stall speed. A centrifugal fan alone cannot maintain a constant airflow over a varying flow rate. Another issue with centrifugal fans is maintenance. Because of the positioning of the motor and the fan, it can be difficult or impossible to perform maintenance on the motor without removing the fan unit. This can be very time-consuming.

Noise

If you compare the amount of air moved against the amount of noise the fan or blower makes, then you would find that blowers produce less noise than axial fans of the same size. The reason is the increase in fan speed. Since axial fans have to rotate at a higher speed than a similar-sized centrifugal fan, the axial fan will produce more noise.

Blower Motor Specifications

Blowers are equipment that increases the velocity of air. Blowers are used in a wide variety of applications from automobile heating and cooling systems to industrial process ventilation systems. Blowers typically consist of blades or vanes that spin at a high rate pulling in air from one side and expelling it at a high velocity on the discharge size. Each application requires specific air flow requirements that are driven by blower motor specifications.

Horsepower and Environment

The required air flow on the discharge of a blower is a function of the size and configuration of the blower fan blades as well as how fast the blades spin. The revolutions per minute of the blades are a function of the blower motor horsepower. Horsepower is a unit of energy that correlates electrical energy input to mechanical energy output. Some industrial applications require blower motors to operate in a hazardous or flammable atmosphere. Blow motor specifications for these applications require intrinsically safe motor designs to avoid ignition sources.
Horsepower is a unit of energy and an important motor specification.

Installation and Configuration

Blower motors contain a central rotating shaft that converts electrical energy into mechanical energy. The shafts can be coupled to the fan blades directly or have intermediate components such as gears or pulley belts. These components can increase or decrease the output force of the blower motor. Space requirements and installation are also an important specification as a blower motor must adequate and safe operating room as well as be protected from any dripping liquids or materials.

Blower motors can be close coupled or belt driven.

Power Requirements

A blower motor must be specified for phase, voltage and direction of rotation. Alternating current has a sine wave characteristic with a peak and a valley for each cycle. Three phase voltage cancels out the peaks and valleys with opposite waves. Consistent power supply such as three phase voltage increases the efficiency of a blower motor. In addition, the voltage of the power source must be specified as 110, 220 or 440 volts. Since a blower operates by spinning fan blades, the direction of rotation is critical to either push or pull air. This must be specified before installation.