Keeping bathrooms, laundry rooms, or kitchens dry with standard ducting systems isn’t always possible, as high humidity levels pose a great challenge for these systems. The best inline duct fans increase the efficiency of the ductwork and remove moisture from damp rooms.
These fans are also utilized to improve ventilation systems of commercial venues or create favorable conditions for the development of plants in grow tents. Their properties depend on the model, and you must make sure that the option you choose is compatible with the ductwork in your home.
You’ll find the information you need to select the best inline duct fan for your ducting in this article. We’re also going to take you through some of the best models that can make your HVAC system more efficient.
Read our guide to ventilation systems for more information about their advantages and disadvantages.
At a Glance – The 5 Best Inline Duct Fans
| Model | Airflow Volume | Duct opening size | Price range |
| AC Infinity Cloudline S4 | 205 CFM | 4 inches | $$ |
| iPower GFANXINLINEEXPC6VEU | 294 CFM | 6 inches | $$ |
| Micromall Inline Duct Fan | 370 – 402 CFM | 6 inches | $$$ |
| TerraBloom ECMF | 710 CFM | 8 inches | $$$$ |
| Vivosun Inline Duct Fan | 440 CFM | 6 inches | $$ |
A smart inline duct fan designed to quietly ventilate hydroponic grow rooms, boost heating/cooling to rooms, circulate fresh air, exhaust projects, and cool AV closets.
Selection Criteria
The selection process of an inline duct fan is likely to be overwhelming if you don’t know exactly what you’re looking for, as there are hundreds of models to choose from.
The ducting size and the purpose for which you want to use the fan are the most important factors that determine which inline duct fan you should get. Let’s take a look at the criteria we used to select the best inline duct fans we featured in this article:
- Inline duct fan’s size – The size of these fans varies from 4 to more than 40 inches, but most models designed for residential use have between 4 and 10 inches. Our selection includes fans that can be used with home HVAC systems.
- Airflow volume – The maximum airflow volume depends on their size. Models capable of generating more than 1000 CFM were not considered because they’re commonly utilized in commercial settings.
- Price-performance ratio – Our selection of inline duct fans includes models that offer a wide range of features and remarkable performances at an affordable price.
Go through our guide to finding the best wall exhaust fan if you want to improve the ventilation system in your bathroom.
How Are Inline Duct Fans and Duct Fan Boosters Different?
These two terms are often used interchangeably, despite the fact that you cannot use inline duct fans and duct fan boosters for the same purposes. Duct fan boosters are primarily utilized to increase the airflow that is circulating through the ductwork, and they can’t be used to ventilate or cool large spaces.
On the other hand, inline duct fans serve a dual purpose since they lower the air humidity and help keep the room cool. These fans have a larger airflow volume capacity than duct fan boosters, but their power consumption is significantly higher.
Accessories like carbon filters and silencers are often paired with inline duct fans to increase their efficiency, eliminate odors and muffle the noise they’re making. Unfortunately, there are no accessories that can help you improve the performance of duct fan boosters.
Browse through our concentric vent guide if you need a vent system that can help you dispose of fumes produced by your gas furnace.
The Benefits of EC Motors
Unlike other types of fans that are powered by AC or DC motors, most inline duct fans are powered by EC or Electronically Communicated motors that combine the features of AC and DC motors.
They run on an alternating current, but their construction resembles more a brushless DC motor equipped with permanent magnets. As a result, they’re more energy-efficient than other types of fan motors, and they also have higher power and torque outputs.
Inlet duct fans equipped with EC motors are easy to install since there’s no need to deal with complex wiring or AC adapters. These motors are controlled through an external circuit board that allows you to have complete control over the fan’s power output.
EC motors are also the reason why inline duct fans are quieter than other types of HVAC system fans. Read our guide to the best HVAC capacitors if you have to replace this component of your HVAC system.
Common Inline Duct Fan Sizes
Inline duct fans are available in a variety of sizes that match the size of duct openings. However, their power output depends on their size, so a 4-inch model will supply considerably lower airflow volume than a 12-inch model.
Besides the airflow capacity of these devices, you should also pay attention to the number of fan speeds they offer. Variable-speed models let you increase the fan speed gradually and provide you with complete control over the fan’s airflow output.
In addition to the fan, you’ll also need to get external and intake vents that are compatible with the ductwork since you cannot install the fan without these components.
The fan’s static pressure depends on its size, and you need to make sure that the static pressure of the model you want to get matches the pressure in the ducting.
Go through our guide to HVAC thermostat systems for more information on how you can use them to control room temperature in your home.
Applications of Inline Duct Fans
Inline duct fans aren’t a standard part of ducting since, in most cases, homeowners don’t need to increase the system’s airflow volume. Most models allow the air to move in both directions, which means that they can supply a room with fresh air and remove the heat from the same room.
These fans are often used to ventilate humid spaces, like kitchens or bathrooms, because they prevent moisture accumulation by increasing the fresh air entering a room. In addition, adding a Y-junction to an inline duct fan enables you to create multiple intake points in the same space.
Connecting a fan and vent that are too far apart is much easier if you add an inline duct fan to the system. Check out our guide on the best HVAC tools to find the tools you’re going to need to install an inline duct fan.
The Most Important Factors to Consider While Choosing an Inline Duct Fan
Finding an inline duct fan you can add to your HVAC system shouldn’t be too difficult since you have countless options at your disposal. However, gathering information about the ducting is a step you need to take in order to know which inline duct fan you should get.
Besides the fan, you might also need other accessories that will increase the system’s efficiency and ensure that the fan has a steady supply of fresh air. So let’s take a look at more factors that can make the search for an inline duct fan quicker and easier.
The Size of the Duct Opening
These fans must be located inside the duct, but you won’t be able to use them if they’re too big or too small for the duct where they should be installed. The best way to determine which size of inline duct fan you need is to measure the size of ductwork.
Standard dimensions of ducts span from 3×7 inches to 35×40 inches, and their diameters range from 4 to 41 inches, so the fan you choose needs to be proportionate to the duct’s size. Most inline duct fans designed for residential use are compatible with ducts that have 4-inch, 6-inch, and 8-inch diameters.
The Maximum Fan Speed and Airflow Output
Checking the fan’s motor specifications will enable you to find out its maximum airflow volume and speed. Nearly all models allow you to choose the fan speed, and in most cases, you can switch between low, medium, and high-speed options.
Variable-speed models offer 6 or more speeds or allow you to adjust the speed setting in the range from 0% to 100%. The airflow volume of these fans depends on their diameter, and it varies from 100 CFM to more than 2000 CFM.
Noise and Vibration Levels
The amount of noise an inline duct is going to make depends on its current load, and most models don’t make humming sounds while operating at low speeds. However, as the load increases, so does the noise level, and it can reach 60dB while the fan is operating at maximum capacity.
That’s why inline duct fans are often installed with silencers that absorb sound waves and vibrations. Some models have built-in sound and vibration-dampening properties, which eliminates the need to purchase accessories that lower the fan’s noise level.
Installation Requirements
Pre-wired inline duct fans are easy to install since you have to properly position them and connect them to a power source. However, pre-wired models are relatively rare, and the majority of inline duct fans need to be hardwired to the furnace or outdoor compressor that switches them on and off.
Hiring an HVAC technician is the safest way to install an inline duct fan because the process involves removing a piece of duct, working with electricity, and putting the duct back together. The installation costs range from $ 100 to $300, depending on the complexity of the job.
Cost and Warranty
Inline duct fans aren’t expensive, and their price ranges from $50 to $300. The accessories such as external and intake vents or carbon filters increase the overall cost of the fans by an additional $200 to $400.
The duration of the warranty varies from brand to brand, but most manufacturers offer warranties that last for 1 to 3 years. You need to check the coverage of the guarantee to learn more about the conditions under which you can replace a malfunctioning fan.
The Advantages of Inline Duct Fans
High Energy Efficiency
Even though they use more wattage than duct fan boosters, inline duct fans still offer high energy efficiency. The power consumption of these fans is unlikely to have a negative impact on your monthly utility bill.
Improved Airflow
Ducts that struggle to distribute air to all parts of a house equally can benefit from inline duct fans because they enable the system to move larger quantities of air. Besides, these fans allow you to create multiple inlet points and improve ventilation in large spaces.
Compatible With All Types of Ducts
You can use these fans with different types of ductwork as long as their sizes match. You only need to know the diameter of the ducting and get an inline duct fan with an identical diameter. The output of the fan is adjusted to the system for which it was designed.
The Disadvantages of Inline Duct Fans
Some Models Can be Loud
Despite having EC motors that are considerably quieter than AC or DC motors, inline duct fans still make a considerable amount of noise. On average, these devices produce between 40dB and 60dB of noise while operating at maximum capacity.
AC Infinity Cloudline S4 – The best 4-inch Inline Duct Fan
Designed specifically for 4-inch ducts, the AC Infinity Cloudline S4 can be used to improve ventilation in grow tents or enhance heating or cooling in a particular area of your home. Its maximum airflow capacity is just 205 CFM, but you can double it by pairing it with an identical model.
The EC motor can produce the maximum fan speed of 2800 RPM, while the PWM manual controller lets you switch between 8 different speeds. The Cloudline S4 is virtually silent since it produces only 28dB of noise at full capacity.
Pros
- Wide range of applications
- Ships with a corded AC adapter
- Easy fan speed adjustment
- Mixed flow construction
Cons
- All accessories must be purchased separately
- Compatible only with 4-inch ducts
A smart inline duct fan designed to quietly ventilate hydroponic grow rooms, boost heating/cooling to rooms, circulate fresh air, exhaust projects, and cool AV closets.
iPower GFANXINLINEEXPC6VEU – The Best Inline Duct Fan for Quick Installation
Getting rid of unpleasant kitchen odors or regulating humidity levels in a greenhouse will be much easier if you get the iPower GFANXINLINEEXPC6VEU inline duct fan. The operating temperature ranges from 40F to 104F, so using this fan at low temperatures is not an option.
The iPower’s model has just three-speed settings, and its maximum fan speed is 2450 RPM. This fan can supply you with a maximum of 297CFM of airflow, and you can only use it with 6-inch ducts.
Removable duct ends enable you to install this inline duct fan quickly, but you can only use it in a vertical position.
Pros
- High power output
- Variable fan speed
- Simple and easy installation process
- Low noise level
Cons
- Short warranty period
- The housing and blades are made of plastic
Powerful blower with a fan speed of 2250 RPM for an airflow of 720 CFM. Moves air through your target location efficiently for optimal ventilation.
Micromall Inline Duct Fan – The Best 6-inch Inline Duct Fan
The dual-ball bearing construction enables you to install the Micromall Inline Duct Fan in vertical and horizontal positions. The mixed flow design allows the air to move through the fan in both directions, so you can use Micomall’s model to get rid of strong odors and supply the room with fresh air.
The energy-efficient EC motor can generate a maximum fan speed of 2500 RPM and provide an airflow volume of 402 CFM. The fan features a controller that lets you program the humidity and temperature settings, and it grants you complete control over the unit’s speed.
Pros
- Capable of creating negative pressure environments
- It makes only 32dB of noise
- The motor doesn’t consume a lot of power
- 2-year warranty
Cons
- More expensive than most 6-inch inline duct fans
- Flimsy construction
Micromall 6” Inline Duct Fan are used in indoor grow facilities and vertical farms, heating and cooling transfer, commercial drying and air filtration applications. 
TerraBloom ECMF – The Best 8-inch Inline Duct Fan
The sturdy coated steel housing protects the TerraBloom ECMF inline duct fan from rust and physical damage. The EC motor consumes just 75W at full capacity, so adding this inline duct fan to your HVAC system isn’t going to increase your household’s monthly or annual power consumption significantly.
The variable speed controller lets you change the fan speed by simply turning the knob, but you can also get an intelligent thermostat controller or remoter controller for this TerraBloom’s model. The fan’s maximum airflow is 710 CFM, while its maximum static pressure is 520 Pa.
Pros
- Zero power waste at low speeds
- All components are durable
- Wide operating temperature range
- High airflow volume
Cons
- Complicated installation process
- It makes more than 60dB of noise
TerraBloom EC duct fans are used in indoor grow facilities and vertical farms, heating and cooling transfer, commercial drying and air filtration applications.
Vivosun Inline Duct Fan – The Most Affordable Inline Duct Fan
If you need a powerful and inexpensive fan for a 6-inch duct, the Vivosun inline duct fan might be the right choice for you. The fan can operate at the maximum speed of 2450 RPM, while its maximum airflow volume is 440 CFM.
The housing is made of Pu leather that lowers the fan’s noise level. The fan’s components that are made of galvanized steel have an anti-corrosion coating that protects them from exposure to humidity. This fan has a manual controller that lets you choose one of the three available speed presets.
Pros
- Aerodynamic design
- Excellent ventilation capabilities
- Low vibration level
- Compatible with most 6-inch ducts
Cons
- High noise level
- Limited speed options
This powerful, heavy-duty blower with a fan speed of 2450 RPM creates an airflow of 440 CFM; It combines the features and benefits of both axial and centrifugal fans to effectively circulate air into your target location, eliminating odors and achieving optimal ventilation.
Frequently Asked Questions About Inline Duct Fans
Question: Where Should I Install an Inline Duct Fan?
Answer: Ideally, an inline duct fan should be located 6 to 10 feet away from the inlet you want to enhance.
Question: How Many Ports do Inline Duct Fans Have?
Answer: An inline duct fan can have one or multiple ports. Single-port models have one exhaust and one inlet duct, while multi-port units have two or more exhaust and inlet ducts.
Question: Do I Have to Clean an Inline Duct Fan Often?
Answer: You don’t have to clean an inline duct fan more frequently than once per year.
Question: Can I Use an Inline Duct Fan at Low Temperatures?
Answer: The operating temperature range of these fans depends on the model, and some units can’t function at temperatures below 40F, while others remain operational even at 0F.
Our Verdict: Deciding Which Inline Duct Fan is the Best for Your HVAC System
Air humidity control and even heating or cooling distribution are some of the greatest benefits inline duct fans offer. Also, you can use them to create specific conditions inside grow rooms or ensure that your bathroom is properly ventilated.
Despite a broad range of available options, you can only use models that are compatible with the ducting in your home. The model you choose should fit inside the duct, and it needs to have matching static pressure and airflow capacities.
We recommend the AC Infinity Cloudline S4 if you have a duct with a 4-inch diameter or the Micromall Inline Duct Fan if you need an inline fan for a 6-inch duct. Hopefully, this article has helped you find the best inline duct fan for your cooling and heating system.
A smart inline duct fan designed to quietly ventilate hydroponic grow rooms, boost heating/cooling to rooms, circulate fresh air, exhaust projects, and cool AV closets.
Let us know in the comments, or continue reading our guide to the best HVAC tape that can help you prevent air leakage after you add an inline duct fan to your HVAC system.
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