What the BDF series is for
BDF is our inline duct booster fan range, designed for supply, exhaust and return air duties in commercial and light commercial HVAC systems where the duct run imposes real resistance.
Typical applications include washroom and utility exhaust in multifamily and hospitality buildings, kitchen and laundry room ventilation in commercial settings, ducted supply and transfer air, and any run long enough or convoluted enough that an axial fan would not hold its airflow.
Range
The series covers duct sizes from 4 to 12 inches, with airflow from approximately 120 to 950 CFM depending on model and operating pressure.
Because these are centrifugal fans with backward-curved impellers, the useful part of that range extends into pressures where an equivalently sized axial fan would have stalled.
Construction
The housing is heavy-gauge galvanized steel. The impeller is backward-curved and dynamically balanced.
The fan can be mounted in any orientation, which matters in ceiling voids and risers where the ideal orientation is rarely available.
Access for cleaning and service is a design consideration rather than an afterthought, because inline fans in exhaust duty accumulate deposits and the ones that never get cleaned are the ones that are difficult to open.
Motor
BDF fans use external rotor motors, in which the rotor forms the outside of the motor and the impeller mounts directly to it. This construction is compact, has no belts or couplings to maintain, and is cooled by the airstream it is moving.
The motors are UL Recognized Components under file E535031, covering both the United States and Canada. Thermal protection is integral.
Because the impeller is backward-curved, the power characteristic is non-overloading: if the installed system turns out to have less resistance than calculated, motor power does not run away.
Certification
BDF fans are ETL Listed with the cETL designation, certified by Intertek under the product category Ducted Fan: to UL 507, Electric Fans, Edition 10 (2017) with revisions through 22 June 2022 for the United States, and to CSA C22.2 No. 113 (2018), Fans and Ventilators, for Canada. Intertek is an OSHA-recognized NRTL and the mark is accepted by AHJs across both countries.
The motors carry UL Recognized Component certification for both markets, as described on our certifications page. We do not publish AMCA Certified Ratings and we are not HVI certified.
Speed control
Single-phase BDF fans are compatible with linear voltage regulators for speed control. Three-phase configurations, available on request, can be driven by a variable frequency drive.
Speed control is worth considering in any application with variable demand. Reducing fan speed reduces airflow proportionally, pressure with the square of speed, and power with the cube — so a modest speed reduction produces a disproportionate energy saving.
Availability
BDF fans are stocked in Houston, Texas and ship from there. This is the practical reason to consider the series on a project with a schedule: the units are on the ground in the United States rather than on a vessel.
How to select
Send us your duty point — airflow in CFM and external static pressure in inches of water gauge — along with duct size and electrical characteristics, and we will return a selection with the performance curve.
You can also run the selection yourself in our fan selection software, which will show you where your duty point falls on the curve rather than simply returning a model number.
Frequently Asked Questions
What duct sizes does the BDF series cover?
4 through 12 inches, in the round duct sizes standard in North America.
Are BDF fans suitable for continuous duty?
Yes. They use external rotor motors with integral thermal protection, designed for continuous operation.
Can BDF fans be mounted vertically?
Yes. The series can be installed in any orientation.
Are BDF fans certified for Canada?
Yes. The fans carry the cETL designation, certified to CSA C22.2 No. 113 (2018), and the motors are separately UL Recognized for Canada under CSA C22.2 No. 77 and No. 100.
Can BDF fans be speed controlled?
Yes. Single-phase units work with linear voltage regulators; three-phase units, available on request, work with a VFD.