AC Infinity Automatic Duct Fan 4-Inch Inline with Differential Pressure Switch and 5-Speed PWM EC Motor

Smart, automatic airflow when you need it

The AC Infinity Automatic Duct Fan 4-Inch Inline is a purpose-built booster designed to improve airflow in longer duct runs, helping heating or cooling deliver more consistently to spaces that sit at the end of the line. The result is a more balanced temperature feel across rooms or zones, without manual adjustments or constant monitoring.

Central to its intelligence is a differential pressure switch that detects changes in duct pressure and automatically activates the fan when your system requires extra air movement. This automatic activation supports a smoother, on-demand ventilation flow as your HVAC or appliance turns on, making it a practical addition for both home and light industrial setups. The sensor supports mounting in any direction, so you can direct airflow vertically, horizontally, or diagonally to fit your duct configuration.

Flexible installation for any duct layout

Designed for 4-inch ducts, this inline fan fits neatly into a variety of spaces and orientations. The compact footprint (6.9 x 11.9 x 7.4 inches) and versatile mounting options help you position the unit where airflow is most effective, even in tight, hard-to-reach areas. If you’re upgrading an existing system or designing a new one, this fan offers a straightforward way to extend effective heating or cooling delivery through long ducts.

Quiet, efficient operation with precise control

Equipped with a next-generation EC motor and PWM control, the fan delivers quiet, energy-efficient performance while maintaining consistent airflow. The mixed-flow design contributes to a high static pressure rating, enabling reliable air movement through restricted sections of ducting—ideal for industrial spaces, bathrooms, or centralized HVAC runs in homes.

Key capabilities and technical snapshot

• Inline duct booster to enhance airflow in long runs
• Automatic activation via differential pressure switch eliminates manual adjustments
• Mountable in any position for versatile airflow direction
• Five PWM-controlled speeds for precise ventilation levels
• Duct Size: 4 inches | Dimensions: 6.9 x 11.9 x 7.4 in | Airflow: 230 CFM | Noise: 60 dBA | Bearings: Dual Ball

What this means in real-world use

In residential settings, the fan can help push warm or cool air further from the furnace or AC, supporting more even temperatures across rooms. In industrial or workshop environments, it offers dependable airflow through extended ducting, reducing hot or stagnant air pockets and contributing to a more comfortable workspace. While performance will vary with duct length and layout, users can expect a practical boost in airflow and a quieter, more efficient system overall.