Centrifugal exhaust fan

Types of Centrifugal Exhaust Fans

Centrifugal Exhaust Fans are devices that move exhaust air from certain areas to other parts of the environment. They are designed for a specific purpose but basically fall into two main categories: the type of air or gas they extract and the installation method needed.

• By the Type of Air or Gas they Extract:

  Centrifugal fans are used to extracting normal air. However, because of the design of the blades, they could be used to extract light gaseous chemicals. Therefore, they are categorized as chemical exhaust fans. Besides that, the heavy-duty centrifugal exhaust fans are used to extract smoke from the environment, such as kitchen smoke. The blades are designed to work efficiently to eliminate smoke.

• By Installation Method:

  When used to extract air from a certain environment, the centrifugal extractor fan is usually installed in a way that creates a certain level of room pressure. Therefore, it is usually installed either directly to a duct or in a way that creates an open-stream duct. In the open-stream setting, the fan is within the vicinity of the open duct, which could be a cupola positioned above the furnace. This open cupola is used to extract air from that specific area.

The direct method of installation is used to connect ducts that take in the air from a further distance. In this case, a centrifugal exhaust fan would be utilized to help the system work better and take in more air.

Another way to possibly categorize a centrifugal extractor fan is by its rotational direction. Some centrifugal exhaust fan suppliers have said that these fans could extract air from the room when it's installed to blow air out. In that case, it's called an axial extraction fan. However, when it's used to suck in air into the environment, it's referred to as a centrifugal exhaust fan.

Some manufacturers may categorize an exhaust fan by the motor that's used to power it. In this case, they could classify it into DC motor centrifugal exhaust fans and AC motor centrifugal exhaust fans. The direct current motor is usually smaller and more compact in design. On the other hand, an AC motor centrifugal exhaust fan is powered by alternating current and is larger in size.

Specifications and Maintenance

The following are specifications people should know about the centrifugal exhaust fan:

• Sizes

  Centrifugal fans and blowers come in a variety of sizes to accommodate different applications. The size of the fan or blower is determined by the wheel diameter, case length, and overall dimensions of the fan. Small centrifugal fans measure about 60 * 60 * 35 mm or 2.4 * 2.4 * 1.4 inches, while large centrifugal exhaust fans range from 200 to over 700 mm (7.9 to 27.6 inches) in wheel diameter.

• Airflow

  The air pressure outlet of a centrifugal fan is high, therefore, it moves a high volume of air. The airflow it moves is determined by the revolutions per minute (RPM) of the motor, the wheel diameter, the air density, and the static pressure requirements of the application. Small centrifugal fans achieve an airflow of about 10 to 97 cubic feet per minute (CFM), while larger models achieve over 200 CFM. For instance, some centrifugal roof exhaust fans can achieve an impressive airflow of 10,000 CFM or even more.

• Material

  The housing and impeller of a centrifugal ventilation fan are usually made of steel, aluminum, or plastic. Steel and aluminum are used for industrial applications because of their durability. The plastic material is widely used for domestic ventilation, such as bathrooms.

• Pressure

  Centrifugal fans have different pressures. The static pressure is related to the resistance generated from the entire system where the fan is used. Some applications need high-static pressure fans because they have ducts and filters that create resistance. Others use normal pressure fans. Normal fans cannot overcome high resistance; hence, they are more efficient.

• Noise Level

  The noise levels of centrifugal fans and blowers are measured in decibels (dB). Smaller models usually make more noise. Their noise level ranges from about 40 dB to 72 dB. The noise level of larger centrifugal fans is less because they use larger blades that rotate at lower speeds. The speed at which the blade rotates also affects the noise level. Larger models have a noise level of about 60 to 85 dB, while some large industrial centrifugal exhaust fans range up to 90 dB or higher.

Maintenance

Some central exhaust fan kits and most centrifugal exhaust fans are maintenance-free. However, to ensure they work for a long time, users may have to do simple routine maintenance. Here are some tips:

• Periodically inspect the visual indicator on the centrifugal exhaust fan. If there is a change in color or any other noticeable change in the tape, it's time to clean the filter.
• Check for any warning signs or abnormalities, such as a change in the noise level, a sudden increase in exhaust noise, a new vibration, or a reduction in centrifugal fan performance. Any of these signs may indicate that the function of the fan has changed. So it is essential to examine it closely and schedule maintenance as soon as possible.
• Use a vacuum cleaner and a brush to remove any dust or debris from the blade and housing of a centrifugal exhaust fan.

Applications of the Centrifugal Exhaust Fan

Centrifugal exhaust fans are versatile equipment and have many applications around them indoors and outdoors.

Industrial Facilities: Factories with automated production lines require efficient ventilation systems for constant fresh indoor air and as a vital component of smoke control systems.

The Food Processing Industry: Refrigeration plants, cold storage warehouses, and food processing factories must maintain a safe indoor environment free from microbial contaminants. Centrifugal exhaust fans fulfill this requirement.

The Construction Industry: Centrifugal exhaust fans are used for concrete curing and tunnels & trenches for dirt and fume extraction. In mines, they help prevent workers from being exposed to toxic harmful gases. They do this through the provision of fresh air underground.

The Chemical Industry: Chemical storage facilities, laboratories, and chemical processing plants require chemical-resistant centrifugal exhaust fans for solvent recovery and fume extraction applications.

The Power Generation Industry: Power plants must make use of centrifugal exhaust fans with efficiency and durability. These are essential for the safe operation and optimal performance of the facility.

The Waste Management Industry: Centrifugal exhaust fans are majorly used in waste treatment facilities for odor control and to ensure the safe ambient air quality is maintained.

How to choose a centrifugal exhaust fan

Selecting the right centrifugal exhaust fan for a particular application involves a careful assessment of various technical and design factors.

• Flow rate and horsepower

  The power that a centrifugal exhaust fan puts out is essential for determining how much air the fan can move. A fan's air flow is gauged by its flow rate, typically measured in cubic feet per minute (CFM). To pick an appropriate fan, one must evaluate the ventilation requirements of the space or the appliance. The fan's flow rate must be in line with the amount of air exchange required. On the other hand, horsepower (HP) is a measurement of the fan's motor power. It determines how much energy the motor needs to work. Choosing a centrifugal exhaust fan with the right horsepower ensures that the motor has enough power to drive the fan. A fan with insufficient horsepower may struggle and become inefficient in carrying out its exhaust duties. By assessing the flow rate and horsepower of a centrifugal exhaust fan, a user will find a suitable model that operates efficiently and utilizes energy effectively.

• Design, efficiency, and noise level

  The task at hand will inform the suitable design of a centrifugal exhaust fan. Some designs are more efficient than others. For instance, a backward-inclined design allows for higher static pressure and air distribution with little energy consumption. It operates at a low noise level but is somewhat inefficient in moving an enormous volume of air. If business buyers are after a model that is very efficient in air movement, a model with a forward-bent blade is a great choice. Even though it may be loud, it works excellently in exhausting air. Centrifugal exhaust fans can get quite noisy in some applications. It may be important to consider a model that produces less noise. A fan with a high airflow rate may be a bit noisy, but choosing one with decent horsepower and efficiency goes a long way in reducing noise.

Centrifugal Exhaust Fan Q & A

Q1: What makes a centrifugal fan different?

A1: Unlike others that push air straight from the intake, a centrifugal fan changes the direction of air intake by converting the energy from the rotating impeller to increase the pressure by throwing it outwards or radially.

Q2: What happens if a fan is too big or small?

A2: A centrifugal fan that is too big will move more air but may use excess power or noise. One that is small may not move the required volume of air to meet the intended purpose. It is better to use a smaller one than a bigger one because it may be easier to dampen the air movement.

Q3: How are centrifugal fans measured?

A3: The size of a centrifugal exhaust fan is measured by the diameter of its wheel or impeller. Common sizes are 4 to 12 inches, but bigger ones are available. The static pressure is also measured, which indicates the resistance the fan can overcome when pushing air through ducting and equipment.

Q4: Do centrifugal fans run continuously?

A4: They are generally designed to run continuously but may run in ON-OFF cycles if used with equipment that operates intermittently, like a furnace that may run only when there are demands for heating. Some may run for about 18 hours a day.

Q5: How long can a centrifugal fan run?

A5: Manufacturers of some fans recommend a maximum continuous run time of 12 hours. If it is used to ventilate a basement, shutting it down after 12 hours may be good unless there is a flood.