Some people call it a blower, while others call it a fan. Others even call it a blower fan. Regardless of the term you use, the fan in an HVAC system is one of the most important components.

Fans generate movement of air throughout your premises and allow for more cool air to be produced from the compressor. They also remove warm air from the room and replace it with a fresh, cool supply. Not all fans are constructed the same way. Some consist of large, open blades, while others have forward curved blades that work via a centrifugal force.

Here are four common types of fans used in HVAC systems.

1. Propeller fans

Also known as axial fans, propeller fans are the most common types of fans used in HVAC systems. Propeller fans are the typical noisy fans that move large amounts of air due to a pressure differential within the unit itself.

Their basic design is a central disk that contains a series of fan blades and a motor (connected to provide power to the fan). Propeller fans come in handy when using portable ACs, cooling towers, outdoor ACs and other similar equipment.

2. Tube-axial fans

Tube-axial fans are slight variations of propeller fans. They feature most of the same construction, except that the fan is present within a tube-shaped housing (a cylinder that has a direct drive motor attached).

Tube-axial fans are used in air conditioners that are shaped in a unique tube-like design. They're also used in cooling towers and outdoor ACs to effectively circulate air.

3. Centrifugal fans

For central air conditioning systems that use ducts and vents, centrifugal fans are most commonly used. These fans look much like waterwheels, and they produce more noise (and consume more power) than propeller fans. This is because centrifugal fans need to overcome the static pressure that is present inside ducts and vents.

Centrifugal fans get their name from the fact that air flows in a 90-degree direction from the rotational axis of the fan itself. This air motion is what makes them a good choice for central air systems in many different premises. They maintain a constant flow of air via ducts and vents to keep the entire premises cool.

4. Backward-inclined fans 

A backward-inclined fan is exactly what its name suggests. It is a fan that has reversed blades that serve to suck out air from specific areas. These fans work in much the same way as centrifugal fans, but they channel air in an opposite direction. Therefore, they come in handy when collecting dust and recirculating air in the home (for greater energy efficiency).