An air conditioner’s blower or fan is one of the key components that is needed as part of the air conditioning system. The AC blower, also known as the fan, is responsible for circulating cooled air throughout your home. There are basically four types of fans that are commonly used in HVAC equipment. They are the propeller fan, centrifugal fan, vane-axial fan, and tube-axial fan.
What Does an AC Blower Do?
The primary role of an AC and heat pump blower is to move cooled air from your air conditioner through your ductwork and into your home’s living spaces. It works in conjunction with the evaporator coil (filled with refrigerant), which cools the air, and the condenser unit with the compressor, which releases heat outside. Without a properly functioning blower, your air conditioner will be unable to distribute cool air effectively.
Types of Air Conditioner Blowers and How They Work
As I mentioned earlier, there are four main types of AC blowers – propeller fans, centrifugal fans, vane-axial fans, and tube-axial fans. Each type has unique characteristics and is suited for different types of AC units. Let’s take a closer look at each type:
Propeller Fan
You will probably encounter this type of fan in your daily life. It has a disk-type wheel mounted on a plate with a direct drive or belt-driven motor connected to it. When it is operating, it is noisy and is only used in applications where noise is not a factor. Look out for its usage as an exhaust and condenser fan.
It is used in applications where low-pressure differentials but large volumes of air movement are required. It is also known as an axial fan, as the air flows parallel to the axis of rotation of the fan.
Centrifugal Fan
This type of fan is also known as a radial fan, as the air flows perpendicularly to the axis of rotation of the fan. Here are the major types of centrifugal fans:
Forward Curved
One category of the wheel design is the forward curved centrifugal fan, which is also known as a squirrel cage blower. It has a forward curved blade with a cut-off design that prevents the air from going around the fan housing.
It is quieter than the propeller type and provides high differential pressure between the inlet and outlet. This type of fan is suitable to be used to move air in the ducts around the building.
Backward Inclined
Backward inclined with a flat and single-thickness metal blade is another design that is used for smaller unit applications.
Backward Curved
Backward curved with curve and single thickness metal fan blade is used in medium and high static pressure applications.
Airfoil
Airfoil with a curve and double-thickness metal blade design is sometimes used. Its aerodynamic design makes it a popular design in applications where efficiency and quietness are required.
Vane-axial Fan
This design has a disk-type wheel, which is housed in a cylinder tube. Air guide vanes are built into the tube to guide the flow of the cold air properly.
Tube-axial Fan
This design has a propeller inside the cylinder with a belt-driven or direct-drive motor connected to it.
Permanent Split Capacitor (PSC) Motor
In air conditioner blowers where the motor capacity is 5 tons or below, a direct drive permanent split capacitor motor has been used due to its better reliability and fewer parts to maintain compared to the belt-driven type. The belt-driven type has pulleys and fan shaft bearings that will wear off over time; hence, regular servicing is required.
The PSC motor has a RUN winding, START winding, and a RUN capacitor, which is active when the motor is running. It is quiet and starts slowly before running at a steady state speed. The fan turns at the same speed as the motor, and a multi-speed fan can be achieved.
You can see many wires coming out of the windings of the motors for speed selection. Four fan speeds with speeds ranging from 800 rpm to 1500 rpm are commonly available. By using relays to select the windings to be connected to the AC power supply, the speed of the air conditioner blower can be controlled.
Related: What is a Fan Speed Controller?
Troubleshooting an AC Blower That’s Not Working
If your cooling system’s blower isn’t working, there are several potential causes. Here are some common issues and how to address them:
- Check the thermostat settings to ensure the fan is set to “on” or “auto.”
- Inspect the air filter and replace it if it’s dirty or clogged.
- Verify that the blower motor is receiving power. If not, check the circuit breaker or fuses.
- Listen for unusual noises from the blower fan, which may indicate a need for repair or replacement.
- If the issue persists, contact a professional HVAC technician for further diagnosis and repair.
Final Thoughts
Regular maintenance, such as replacing air filters and scheduling annual service with a professional HVAC technician, can help prolong the life of your AC blower and ensure the best performance. If you experience any problems with your blower, don’t hesitate to contact a qualified HVAC technician for assistance.
Frequently Asked Questions
What is the difference between a single-speed and variable-speed AC blower?
Single-speed blowers operate at a constant speed, while variable-speed blowers can adjust their speed based on cooling demands, providing more efficient and even cooling from your HVAC system.
Can a dirty air filter affect the AC blower's performance?
Yes, a dirty air filter restricts airflow, causing the blower to work harder and potentially leading to overheating and premature wear.
How often should I have my AC blower serviced?
I recommend having your AC system, including the blower, serviced annually by a professional HVAC technician to ensure optimal performance and longevity.
