Duct Booster Fan Reviews
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Duct Booster Fan Reviews

Review of various types of duct booster fans as well as the 3 most common manufacturers.

Many homes with old or inefficient heating, ventilation, and air conditioning (HVAC) systems employ duct booster fans to increase airflow to particular rooms to improve the comfort for the occupants.

Duct booster fans can come in several different configurations such as in-line, centrifugal, and even a register mounted style. Each configuration has its advantages and disadvantages as well as limits on the cubic feet per minute (CFM) of airflow each can deliver. There are also universal duct booster fans which are installed in a cutout in the ductwork instead of in line with the duct.

Centrifugal Duct Booster Fan

Installation

Duct booster fans obviously are installed in the duct and boost the airflow to a room or in a branch of ductwork. The amount of airflow varies depending on the construction of the duct after the fan, expressed in static pressure, and the amount of air entering the booster fan.

Duct Booster Fan Schematic

A duct booster fan can supply anywhere from 20 CFM to over 2,000 CFM depending on the size of the fan; keep in mind that 2,000 CFM is enough airflow for a large home.

Smaller fans can be plugged in to a receptacle or hardwired where larger fans are almost always hardwired.

Booster fans installed at the register are probably the least effective and may not be applicable in every instance as they require an electrical receptacle to be within 5 or 6 feet of the wall or floor register. It may be difficult for the register fan to pull the conditioned air through the duct and deliver into the room as these fans are usually less than 100 CFM in size. As they age, noise may be a factor as well.

In-line Duct Booster Fan

Floor or Wall Register  Booster Fan

Manufacturers

There are dozens of manufacturers for duct booster fans, a few of the more common are Tjernlund, Fantech, and Suncourt. Tjernlund makes duct booster fans in several configurations and is highly regarded in the HVAC industry. They also make dryer vent booster fans. Fantech is probably the most common duct booster fan for residential applications and is a built well.

Construction and Warranties

When selecting a duct booster fan you can read reviews from previous buyers on various websites or you can select the fan based on the construction and specifications of the fan. Specifications describe how the fan operated and what components are used in the manufacture of the device.

Some considerations to be aware of are the noise levels and size of the motor. Smaller fans will tend to wear out quicker than larger ones and booster fans installed in ductwork with several turns or restrictions will also wear out faster than normal. Fans with polycarbonate blades, (clear plastic) are typically used for low volume applications and should not be used where more than 100 CFM is required. Look for heavy gauge steel construction and some manufacturers offer warranties of up to 5 years. Always look for fans that are UL or CSA listed and install them according to the specifications so as not to void the warranty.

Universal duct booster fans should not be used unless cost, location, or access is a concern. They typically deliver less than the stated CFM of airflow due to the way they are installed. Carefully read the specifications as some fan manufacturers recommend a reducer coupling be installed before and after the fan to increase the static pressure produced.

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Comments (7)

Fascinating information about duct booster fans. I learned something new today. Thanks!

Well done Daniel.

steve

my eastern rm over garage gets very warm..vent in rm is only 8 ft from evap. unit,,and upstairs unit is 2 1/2 ton for 1000 sq ft. a little undear sized..would a booster blower help for that rm

A booster fan may help, but you may want to try and adjust the registers in other rooms first. Try closing some of the registers or dampers in rooms close to the one over the garage. Depending on how the duct work is run, there may be some turbulence that is reducing the airflow through the register or the balncing damer is closed. If this doesn't work then you may want to install a booster fan.

Rich

before installing a fan, get your hands on a dydrometer, (cfm meter) and see exactly what is coming out of the ducts. Sometimes if you balance the system out you can create more airflow to where you need it.

just an fyi.

Rich, I have never heard of a "dydrometer", but I believe an anemometer can be used to measure the cfm; this article deals with booster fan types, not whether or not there may be needed. I cover this in another article dealing with balancing dampers. Thanks for the tip.

Daniel,

great info here. In a comment you mention another article "how to balance dampers", a link here would be very useful.

also, is there a good article/resource for the lay person on running ductwork/ what should the cfm at registers be and how much each bend deminishes the flow. I have downloaded and looked at a series of duct calculators and they mostly just confuse the issue.

I understand the cross sectional area of the duct and duct length obviously add to flow resistance and each bend (and type of bend 15,30,45,90,180 degree) each effectively add duct distance.

 a great reference i found said add 5 feet for a 45 degree, 10 feet for a 90 degree, 30 feet for a 180 degree in round duct. but if rectangular is used and the connection is the short side of the duct to the long side of the up flowing continuation these simple duct distance rules don't "intuitively" seem right as it seems to be more than a twisted double 90 degree in resistance to flow. 

an article on this topic would be wonderful to find.

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