The term “inline duct heater” is often searched by homeowners and growers wanting reliable ways to move warmed or cooled air through ducting. This guide reviews five popular inline duct fans that are commonly paired with heating or ventilation systems to transfer conditioned air, boost airflow, and manage humidity. Below is a quick comparison of the selected models followed by detailed product sections and a buying guide.
| Product | Size | Key Feature | Best For |
|---|---|---|---|
| AC Infinity CLOUDLINE PRO S4 | 4″ | 10-speed wired controller, PWM EC motor | Small duct runs, grow tents, AV racks |
| AC Infinity CLOUDLINE A6 | 6″ | Value CLOUDLINE with 10-speed controller | Medium duct runs, hydroponic tents |
| AC Infinity CLOUDLINE S8 PRO | 8″ | Quiet EC motor, wired 10-speed controller | Larger rooms, heavier ventilation loads |
| VIVOSUN D4 4 Inch | 4″ | 195 CFM, ETL listed motor, flow deflector | High airflow in compact spaces |
| iPower 8 Inch Inline Booster | 8″ | 420 CFM, centrifugal impeller, durable housing | High-capacity ventilation for basements, attics |
AC Infinity CLOUDLINE PRO S4, Quiet 4” Inline Duct Fan
The AC Infinity CLOUDLINE PRO S4 is a compact 4-inch inline duct fan designed to ventilate grow tents, transfer heating and cooling to rooms, circulate air, and cool AV racks. It includes a wired 10-speed fan controller and is compatible with UIS controllers for advanced programming. The fan uses a PWM-controlled EC motor for quiet and energy-efficient performance with minimal heat and noise. This makes it suitable where space is limited but consistent airflow is needed. The product’s feature set emphasizes controllability and low-noise operation, important when pairing with inline duct heating elements or heat sources where steady airflow preserves temperature distribution.
AC Infinity CLOUDLINE A6, Quiet 6” Inline Duct Fan
The CLOUDLINE A6 provides the same core build quality and innovations of the CLOUDLINE Series delivered as a value package. It’s a 6-inch inline duct fan designed to quietly ventilate grow tents, exhaust odors, and transfer conditioned air between spaces. Included is a wired 10-speed fan controller, and the unit is compatible with other CLOUDLINE smart controllers. The A6’s balance of size and controllability suits medium-length duct runs and applications where slightly greater CFM than a 4″ fan is required, such as larger tents or connecting to an inline heating element for room heat transfer.
AC Infinity CLOUDLINE S8 PRO, Quiet 8” Inline Duct Fan
The CLOUDLINE S8 PRO is an 8-inch inline duct fan intended for larger grow rooms, AV closets, and heavier ventilation requirements. It includes a wired 10-speed controller and a PWM-controlled EC motor for quiet and energy-efficient operation. Features focus on moving larger volumes of air while keeping noise and heat generation low, which is essential when distributing warm air from a heater or removing heat from equipment. Compatibility with UIS controllers allows integration into automated climate setups where temperature-based speed adjustments are needed.
VIVOSUN D4 4 Inch 195 CFM Inline Duct Ventilation Fan
The VIVOSUN D4 is a 4-inch inline duct blower rated for up to 195 CFM, driven by a 2500 RPM motor. It’s designed to ventilate grow tents, transfer heat or cool air, and maintain humidity and temperature control. The unit includes a flow deflector to concentrate airflow and reduce turbulence, producing a lower sound output reported around 30 dB. The motor is ETL listed and offers an automatic reset function to guard against overheating. For users needing high airflow from a small diameter fan—especially when paired with inline heaters or duct heaters in tight spaces—this blower emphasizes airflow and safety features over controller sophistication.
iPower 8 Inch Inline Booster Duct Fan 420 CFM
The iPower 8-inch inline booster fan delivers up to 420 CFM with a centrifugal impeller and robust housing. It’s intended for larger ventilation tasks in grow tents, basements, bathrooms, kitchens, or attics. The motor uses a permanently lubricated bearing for maintenance-free operation. Noise is described as under 40 dB at typical operating conditions, which balances performance with acceptable acoustic levels. The model includes a grounded power cord and is sized for installations where higher capacity airflow is required to move heated or cooled air efficiently through long or larger-diameter ducting.
Buying Guide: Choosing The Right Inline Duct Fan For Heating
Inline duct fans are used to move conditioned air from a heater, heat exchanger, or HVAC system through ducting to target spaces. Selecting the right model requires balancing airflow (CFM), static pressure handling, noise, motor type, mounting constraints, and control options.
Key Specifications To Evaluate
- CFM (Cubic Feet Per Minute) — Choose CFM based on room volume and desired air-exchange rate; higher CFM moves more air but may be louder and require larger ducts.
- Duct Size Compatibility — Match fan diameter to duct diameter to avoid backpressure or inefficient airflow.
- Static Pressure Rating — If duct runs include bends, filters, or length, pick a fan with sufficient static pressure capacity to maintain rated airflow.
- Motor Type — EC (electronically commutated) motors offer higher efficiency and quieter operation than standard AC motors; look for PWM control compatibility for fine speed adjustments.
- Noise Level — Measured in dB; lower values are better for living spaces or AV closets. Consider mounting location and vibration isolation.
- Control Options — Simple multi-speed controllers, smart controllers (WiFi, temperature/humidity-based), or UIS integration allow automation and finer climate control.
- Safety Certifications — ETL or UL listings indicate adherence to electrical safety standards. Overheat protection is helpful when pairing with inline heaters.
- Durability & Maintenance — Permanently lubricated bearings reduce maintenance; check housing materials and ease of cleaning.
Performance And Application Perspectives
- Small Rooms And Grow Tents — 4″ and 6″ fans with moderate to high CFM are typically sufficient. For tight spaces, compact models like the CLOUDLINE PRO S4 or VIVOSUN D4 offer strong airflow with small footprints.
- Medium To Large Rooms — 6″ to 8″ fans provide greater volume. The CLOUDLINE A6 and S8 PRO fit medium applications with controllability; iPower 8″ or CLOUDLINE S8 PRO handle larger requirements.
- High Flow Or Long Duct Runs — Choose models with higher static pressure and CFM such as the iPower 8″ to overcome resistance from long runs or multiple bends.
- Noise-Sensitive Areas — EC motor fans with PWM speed control typically run quieter. Evaluate published dB levels and consider insulating mounts.
- Heating Integration — When pairing with an inline duct heater, ensure the fan’s airflow is appropriate to prevent overheating the heater element and to achieve even heat distribution. Fans with variable speed help tune air temperature output.
Installation And Compatibility Considerations
- Mounting Orientation — Verify whether the fan supports vertical or horizontal mounting when used with duct heaters; some motors rely on orientation for cooling.
- Electrical Requirements — Confirm voltage and cord length; some units include grounded cords or require separate controllers wired to the fan.
- Controller Integration — If automation is needed, pick models compatible with smart controllers or add-on sensing modules for temp/humidity-based control.
- Duct Transitions — Use appropriate adapters when pairing different diameters; avoid abrupt transitions that increase turbulence and pressure loss.
Safety And Longevity Tips
- Ensure fans have thermal overload protection when used with inline heaters to reduce fire risk.
- Allow proper clearance around the fan housing for ventilation of the motor if required by the manufacturer.
- Regularly inspect and clean impellers and housings to maintain performance and reduce noise.
- Use vibration isolation straps or mounts to reduce noise transmission into building structures.
Comparison Summary
- AC Infinity Models — Strong on intelligent controllers, EC motors, and quiet operation; ideal for users who value automation and low noise.
- VIVOSUN D4 — Emphasizes high CFM for its 4″ size and safety features like ETL listing; suitable for compact high-flow needs.
- iPower 8″ — Focuses on raw airflow and durable construction for larger ventilation tasks where capacity is the priority.
Selecting the right inline duct fan depends on the duct diameter, required airflow (CFM), noise tolerance, and whether you need smart control or simple speed adjustment. For pairing with inline duct heaters, ensure the fan can supply consistent airflow at the operating temperature and that safety certifications and overheat protections are in place.