The only way you could make this unit work with rectangular ducts would be to get adapters to go from rectangular duct to round duct then another adapter to go from round back to rectangular. As the staff member indicated, there are other fans that are intended for use with rectangular ductwork.
Tjernlund Duct Booster Fan, 300 CFM, 120 Volt

This is a carousel with one large zoomable image and a track of thumbnails on the left. Select any of the thumbnail buttons to change the zoomable image on the right. If a thumbnail is a video or 360 degree image thumbnail, or the last thumbnail in the list, the button will open the product media modal.

Click or Tap image to Zoom
Shipping:
Factory shippedStore Pickup:
Not available - online only
- Powerful Airflow (Up to 325?CFM): Delivers robust airflow in 8? ducts, helping overcome static pressure drops and ensuring even heating or cooling in distant or underserved areas of your home.
- Heavy-Duty Galvanized Steel Housing: Built for durability and heat resistance (up to 150?°F), this robust housing protects the motor and blade assembly and withstands long-term use in HVAC systems.
- Metal Fan Blade with C-Frame Motor: Equipped with a high-performance metal fan blade and C-frame motor architecture for consistent speed and better pressure-handling capability than plastic-blade models.
- Low Power Consumption: Operates on only 56?W (1.1?A at 120?V), keeping energy usage minimal while still providing significant airflow gains—a more efficient option than running an oversized HVAC blower.
- Minimal Maintenance & Simple Control Options: Designed to work with standard HVAC filters so no blade cleaning is needed. You can control the fan manual on/off, use Tjernlund’s optional SC?1 speed controller, or automate operation with a duct-mounted airstat sensor.
See full description
Description
Key Specs
Reviews
Q & A
Warranty
Compare
Product Summary
What's Included
- (1) Booster fan
Downloads

Features + Benefits
- Powerful Airflow (Up to 325?CFM): Delivers robust airflow in 8? ducts, helping overcome static pressure drops and ensuring even heating or cooling in distant or underserved areas of your home.
- Heavy-Duty Galvanized Steel Housing: Built for durability and heat resistance (up to 150?°F), this robust housing protects the motor and blade assembly and withstands long-term use in HVAC systems.
- Metal Fan Blade with C-Frame Motor: Equipped with a high-performance metal fan blade and C-frame motor architecture for consistent speed and better pressure-handling capability than plastic-blade models.
- Low Power Consumption: Operates on only 56?W (1.1?A at 120?V), keeping energy usage minimal while still providing significant airflow gains—a more efficient option than running an oversized HVAC blower.
- Minimal Maintenance & Simple Control Options: Designed to work with standard HVAC filters so no blade cleaning is needed. You can control the fan manual on/off, use Tjernlund’s optional SC?1 speed controller, or automate operation with a duct-mounted airstat sensor.
Key Specs
| Attribute | Specification |
|---|---|
item# | 18005 |
Brand | Tjernlund |
Manufacturer's Warranty | 1 year limited warranty |
Ship Weight | 4.25 LB |
| Attribute | Specification |
|---|---|
Compatible With | Heating Ducts |
CFM | 300 cfm |
Product Weight | lb |
Dimensions L x W x H (in.) | 8.0 x 9.0 x in |
Reviews
Questions & Answers
Questions
-
· 14 years ago
Ductwork Type?
Is it possible for this to be installed in my existing rectangular ductwork?
-
SoccerDadof2· 10 years ago
Helpful?
-
ProductExpert36· 14 years ago
The booster fan is designed for use with standard 9 inch diameter circular duct. It will not effectively work in square or rectangular ducting. Please see the attached link for a product offered through Northern Tool that would work with your rectangular duct work.
Helpful?
-
-
· 3 years ago
What is the heat limit on fan
1 answer-
ProductExpert13· 3 years ago
The max air temperature this can handle is 150 degrees.
Helpful?
-
-
· 4 years ago
Does this have a permanent split capacitor motor
1 answer-
ProductExpert11· 4 years ago
The blower does not have a permanent split capacitor motor.
Helpful?
-
-
· 4 years ago
Can this fan be used as a variable speed fan when used with a 120V wall mounted dimmer switch?
1 answer-
ProductExpert29· 4 years ago
This booster fan can be used as a variable speed fan when used with the optional speed control from the manufacturer, model #SC-1. It cannot be wired to a dimmer switch for variable speed.
Helpful?
-
-
· 5 years ago
What is the db rating of this fan?
1 answer-
ProductExpert6· 5 years ago
The manufacturer does not rate these booster fans for a decibel rating.
Helpful?
-
-
· 5 years ago
Can this be used in a small chimney to improve draft above a gas grill?
1 answer-
ProductExpert11· 5 years ago
The fans are designed to increase the flow of heated air in a warm air heating system or cooled air in a central air conditioning system. It would not be recommended for this application.
Helpful?
-
-
Anonymous· 5 years ago
I need this in a six inch fan/duct we used to be able to get from you
1 answer-
ProductExpert6· 5 years ago
See our item #18000. This booster fan can be installed in a 5 inch diameter or larger duct.
Helpful?
-
-
· 9 years ago
Is the motor case sealed to prevent dust getting into it?
1 answer-
ProductExpert30· 9 years ago
This item has a C-Frame motor that is not completely sealed however there would be no concern for dust or sparks with this unit.
Helpful?
-
-
· 10 years ago
What is the noise level of this fan?
1 answer-
ProductExpert40· 10 years ago
This fan could have differing sound levels depending on variables such as applications used in and if you were to use a speed controller.
Helpful?
-
-
· 11 years ago
Can you use the 18005 as a primary source fan
1 answer-
ProductExpert7· 11 years ago
This is a booster fan that is designed to enhance air flow to one room only.
Helpful?
-
Warranty
Manufacturer's Warranty
1 year limited warranty
Extend Your Warranty Coverage with a Northern Protection Plan (NPP)
Replacement Plan — 1 Year
A Northern Protection Plan is available after adding the product to your shopping cart.
Compare with Most Popular in Blowers + Fans
See All Blowers + Fans
See All Tjernlund Blowers + Fans
Currently Viewing This Product
Item # 18005
$109.99Shipping:
Factory shippedStore Pickup:
Not available - online only
- $32.99
Shipping:
Not availableIn Store Only:
Sold only in stores -
Bluegrass Living Blower, Fits Bluegrass Living Ventless Fireplace Systems and Inserts, Model# QEB100
Item # 87761
$99.99Shipping:
Not availableIn Store Only:
Sold only in stores -
- $89.99
Shipping:
Factory shippedStore Pickup:
Not available - online only
Specifications
Heating Ducts
20,000 - 30,000 BTU Mr. Heater Vent-free Heaters
Bluegrass Living Ventless Fireplace and Inserts
Pleasant Hearth Vent-free Fireplace
300 cfm
18.5 cfm
-
50 cfm
lb
lb
3.0000 lb
lb
8.0 x 9.0 x in
6.25 x 5.5 x 5.5 in
11.0 x 5.0 x 8.0 in
9.75 x 3.75 x 10.0 in
-
Steel
-
-
-
0.16
15
0.17
-
-
-
20
See All Blowers + Fans
See All Tjernlund Blowers + Fans
Recently Viewed Items
This is a carousel with auto-rotating slides. Activate any of the buttons to disable rotation. Use Next and Previous buttons to navigate, or jump to a slide with the slide dots.



