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Ventilation|Updated 2026-09-30

Inline Fans Compared: AC Infinity CLOUDLINE T4, T6 & S4

Compare CLOUDLINE T4, T6 and S4 inline duct fans by connection size, controller and rated airflow. Check model differences and current retailer prices.

Jump to:#1 T4#2 T6#3 S4

Start with the model and controller, not a star score. This shortlist compares two smart-controller options and a simpler speed-controlled alternative. It is a product-specification comparison, not a hands-on test or an exhaustive market ranking.

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How we compared these products

Specifications below come from the current manufacturer listings, checked September 29, 2026. We have not independently measured airflow or noise. Older versions and retailer bundles may differ; verify the model, controller, included accessories, and current price on the seller page. We omit unverified star ratings and live-price claims.

T4 specificationsT6 specificationsS4 specifications

Compare by connection and controller

4-inch + smart control

CLOUDLINE T4

The smaller T-series model with a programmable controller.

6-inch + smart control

CLOUDLINE T6

The larger duct connection and higher manufacturer-rated airflow.

4-inch + speed control

CLOUDLINE S4

A simpler controller if you do not need built-in climate programming.

At-a-glance comparison

Skip the long write-ups — pick the column that matches your needs and click through.

 
#1Smart 4-inch
AC Infinity CLOUDLINE T4
4-inch with smart controller
#2Smart 6-inch
AC Infinity CLOUDLINE T6
6-inch with smart controller
#3Simple controls
AC Infinity CLOUDLINE S4
4-inch with manual speed control
PriceCheck current priceCheck current priceCheck current price
Duct size4 inch6 inch4 inch
Rated airflow226 CFM (manufacturer)425 CFM (manufacturer)226 CFM (manufacturer)
ControllerController 69 ProController 69 ProTen-speed controller
AppWiFiWiFiNot with included controller
Best forA 4-inch system with programmable controlsA 6-inch system with programmable controlsManual speed adjustment without smart-controller features
BuyCheck T4 Price on AmazonCheck T6 Price on AmazonCheck S4 Price on Amazon
#1Smart 4-inch

AC Infinity CLOUDLINE T4

4-inch with smart controller

Check current price
AC Infinity CLOUDLINE T4

Our Verdict

Compare this model when you need a 4-inch connection and a programmable controller. The current manufacturer listing includes a Controller 69 Pro; confirm the controller in the retailer bundle before ordering.

Best For: A 4-inch system with programmable controls
Check T4 Price on Amazon

Pros

  • +Programmable temperature and humidity controller
  • +WiFi app connection on the current listed version
  • +PWM-controlled EC motor

Cons

  • -More controller features to configure than the S4
  • -4-inch connection is not interchangeable with 6-inch accessories

Key Specifications

Duct size4 inch
Rated airflow226 CFM (manufacturer)
ControllerController 69 Pro
AppWiFi
#2Smart 6-inch

AC Infinity CLOUDLINE T6

6-inch with smart controller

Check current price
AC Infinity CLOUDLINE T6

Our Verdict

Compare the T6 when your equipment uses a 6-inch connection. Its published airflow rating is higher than the T4; that is a manufacturer specification, not a measurement of your installed system.

Best For: A 6-inch system with programmable controls
Check T6 Price on Amazon

Pros

  • +Higher published airflow than the T4
  • +Programmable controller and WiFi app connection
  • +PWM-controlled EC motor

Cons

  • -Larger housing and duct connection
  • -Not a direct replacement for a 4-inch fan

Key Specifications

Duct size6 inch
Rated airflow425 CFM (manufacturer)
ControllerController 69 Pro
AppWiFi
#3Simple controls

AC Infinity CLOUDLINE S4

4-inch with manual speed control

Check current price
AC Infinity CLOUDLINE S4

Our Verdict

The S4 includes speed control instead of the T4’s climate-programming controller. Compare the total cost carefully if you plan to buy a smart controller separately later.

Best For: Manual speed adjustment without smart-controller features
Check S4 Price on Amazon

Pros

  • +Included ten-speed controller
  • +Same published airflow rating as the current T4
  • +PWM-controlled EC motor

Cons

  • -Included controller does not provide climate programming
  • -Do not confuse the S4 bundle with the T4 bundle

Key Specifications

Duct size4 inch
Rated airflow226 CFM (manufacturer)
ControllerTen-speed controller
AppNot with included controller

Inline Fan Buying Guide

CLOUDLINE is not AIRTAP

This comparison covers CLOUDLINE inline duct fans. AC Infinity also uses T4 and T6 names in its AIRTAP register-booster range, which is a different product family. Check the full product name, not just the model number.

Check the exact model

T4, T6, and S4 are different products. A retailer page may group multiple sizes and controllers together. Check the selected variant and what is included before adding it to your cart.

Compare the complete purchase

A fan-only price and a fan/controller/filter bundle price are not directly comparable. Check accessories, shipping, returns, warranty, and the current seller price rather than relying on an old price in a review.

Read ratings as specifications, not test results

This page does not contain independent airflow or sound measurements. Manufacturer ratings describe the listed model, not guaranteed performance in every installation. Follow the product manual for compatibility and installation requirements.

Frequently Asked Questions

What is the difference between the T4 and T6?
The T4 has a 4-inch duct connection and the T6 has a 6-inch connection. Both current manufacturer listings include smart controls. Compare the table and confirm the exact retailer variant before buying.
Have you tested how quiet these fans are?
No. We have not performed independent noise testing, so we do not rank these fans by measured noise or present manufacturer figures as our own test results.
Why are there no star ratings or fixed Amazon prices?
We do not have a verified review-score dataset or a live Amazon price feed for this comparison. The links let you check the current price, stock, seller, and reviews directly.

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