AC Infinity CLOUDLINE S4 4" Inline Duct Fan — Quiet 205 CFM, 10-Speed Controller, 28 dBA

The AC Infinity CLOUDLINE S4 is a compact, whisper-quiet 4-inch inline duct fan with a 10-speed wired controller designed for efficient ventilation in grow tents, AV racks, and small rooms.

Built for environments where airflow, low noise, and energy efficiency matter, the CLOUDLINE S4 pairs a PWM-controlled EC motor with a mixed-flow impeller to move up to 205 CFM while running as low as 28 dBA. Its small footprint and dual-ball bearings ensure long-lasting operation, and the included wired speed controller gives you ten discrete speed settings for fine-tuned ventilation without extra accessories.

How does the CLOUDLINE S4 perform in tight spaces or high-resistance duct runs?

The mixed-flow design, combining stator blades and hydrodynamic wind circles, helps maintain steady airflow even when ducts or filters add resistance. This design pushes air more effectively than conventional axial fans in pressurized conditions, so you keep circulation without oversizing the unit.

• Airflow up to 205 CFM for strong ventilation in small systems
• Mixed-flow impeller improves pressure handling in restrictive ducts
• Compact dimensions (6.9 x 11.9 x 7.4 in) fit congested installations

Is the CLOUDLINE S4 quiet and energy-efficient enough for living spaces?

Yes—its PWM-controlled EC motor minimizes electrical losses and heat, so the fan runs efficiently at lower speeds. At normal operating levels the unit can be nearly silent (rated 28 dBA), making it suitable for bedrooms, offices, or media closets where noise matters.

• Noise rating as low as 28 dBA for unobtrusive operation
• EC motor with PWM control for lower energy consumption
• Dual ball bearings for reliable, low-friction rotation over time

What control options and compatibility does the fan offer?

The CLOUDLINE S4 ships with a wired 10-speed controller that provides immediate manual adjustment across a wide range. For more advanced scheduling or automation, it’s compatible with AC Infinity’s UIS controllers which add intelligent programming and environmental feedback.

• Included wired 10-speed controller for simple, instant control
• Compatible with UIS controllers for timers, thermostats, and humidity control
• Multiple speed steps let you balance airflow and acoustics precisely

How durable and serviceable is the fan for continuous operation?

The CLOUDLINE S4 uses dual ball bearings and a robust housing to handle continuous duty cycles in demanding setups. With proper installation and periodic cleaning, the fan is built to provide years of consistent ventilation without frequent maintenance.

• Dual ball bearings for longer life and stable performance
• Sturdy mixed-flow housing that resists vibration and wear
• Easy-to-access controller and mounting points for straightforward upkeep

Who is this for: The AC Infinity CLOUDLINE S4 is ideal for hobby growers, home theater or AV installers, and anyone needing a compact, quiet inline fan for small to medium enclosures. Choose this model when you want a balance of strong airflow, low noise, and the flexibility of manual or UIS-compatible control in a small footprint.