The AC Infinity CLOUDLINE PRO S4 is a 100 mm (4″) inline duct fan for small spaces that still need real air movement — 384 m³/h · 107 L/s (226 CFM) from a mixed-flow impeller and a PWM-controlled EC motor, paired with a corded 10-speed dial rather than a smart controller. At 26 dBA it is the quietest fan in the CLOUDLINE range, which is why it ends up in AV cabinets, small tents, laundries and single-room transfer runs as often as it does in a grow space. If you want a fan you set once and forget about, this is the one.
Set-and-forget speed control
The included controller is a corded dial with ten speed levels and backup memory — cut the power and it returns to the setting you left it on. No menus, no app, no probe to position. For a cabinet, a small tent or a bathroom-to-outside run where conditions barely change, that is usually all the control the job needs, and it is the reason the S4 costs less than the T4.
The controller mounts with the supplied hardware and sits on a 3.05 m lead, so it can live outside the space the fan is in. Speed changes are handled by the EC motor through PWM rather than by choking voltage, so the low settings stay smooth and quiet instead of humming.
Quiet, energy-efficient performance
Most cheap duct fans use an AC motor — loud, one-note, and only crudely controllable. The S4 uses a PWM-controlled EC motor, which is why it can idle at genuinely low noise and why it draws so little power: 21 W average, 28 W maximum. That draw also falls away steeply as you dial the speed back, because fan power scales with roughly the cube of speed. An AC-motor fan pulls close to its full rated wattage the moment it's switched on, whatever speed you've set it to.
The mixed-flow design and 223 Pa static-pressure rating are what hold airflow up once you add a filter, a bend or two and some flexible duct. Be realistic about that figure though — it is the lowest in the CLOUDLINE range, and a 100 mm carbon filter on a long run will take a meaningful share of it. AC Infinity rate the dual ball bearings at 67,000 hours, the fan mounts horizontally or vertically, and the motor box detaches from the frame so you can pull it out and clean the impeller without dismantling your ducting.
What people use it for
Home ventilation
- Bathroom, laundry and ensuite exhaust (ducted)
- Single-bay subfloor and underfloor extraction
- AV cabinets, racks and equipment cupboards
- Small workshops, studios and hobby rooms
- Room-to-room air transfer
Hydroponic ventilation
- Grow tents up to 0.9 × 0.9 m (3×3)
- Propagation and small hobby setups
- Fresh-air intake on a larger tent
- Light heat and humidity extraction
- Quiet setups where noise matters more than volume
Full specifications
| Manufacturer | AC Infinity Inc. |
| Product / model | CLOUDLINE PRO S4 / AI-CLS4 |
| UPC | 819137020290 |
| Duct diameter | 100 mm (4″) |
| Fan dimensions | 188 × 303 × 176 mm |
| Mounting-hole spacing | 80 × 60 mm |
| Screw-hole diameter | 5 mm |
| Cord to controller | 3.05 m |
| Power cord | 2.44 m |
| Controller | Corded 10-speed dial with backup memory |
| Maximum airflow | 384 m³/h · 107 L/s (226 CFM) |
| Maximum noise | 26 dBA |
| Static pressure | 223 Pa |
| Voltage / frequency | 100–240 V AC / 50–60 Hz |
| Maximum / average power | 28 W / 21 W |
| Current | 0.4 A |
| Power connection | Australian three-pin plug |
| Operating range | 0–60°C / 35–85% RH |
| Ingress protection | IP44 |
| Mounting | Horizontal or vertical |
| Bearings | Dual ball |
| Rated bearing life | 67,000 hours (manufacturer rating) |
| In the box | Fan unit, corded 10-speed speed controller, two duct clamps, mounting hardware, manual |
| Certifications | SAA · CE · ETL · RoHS · IC |
| Product manual | CLOUDLINE S & T series manual (PDF) |
FAQ
What's the difference between the CLOUDLINE S4 and the T4?
The fan itself is identical — same motor, same impeller, same 226 CFM. The difference is control. The S4 comes with a corded 10-speed dial. The T4 comes with the Controller 69 Pro, which adds temperature, humidity and VPD triggers, dynamic speed, timers, schedules and WiFi app control. If you'll set a speed once and leave it, the S4 saves you money. If you want the fan reacting to conditions on its own, you want the T4.
What size grow tent will a 100 mm fan handle?
For growing, the S4 suits tents up to 0.9 × 0.9 m (3×3). That is a grow-tent rating, not a room limit: it allows for a carbon filter, the heat from the lights and roughly one full air change every minute, which is far more work than ventilating a room in a house. If you are running a 1.2 × 1.2 m (4×4) tent, or a carbon filter on more than a couple of metres of ducting, buy the S6 instead. A 4″ fan pinned at level 10 to keep up is louder, hotter and shorter-lived than a 6″ fan loafing at level 5, and it will still move less air. For a bathroom, laundry or other room in the home, see the questions below.
Will it pull properly with a carbon filter attached?
It will, within limits. The mixed-flow impeller holds pressure far better than a straight axial fan does, but 223 Pa is the lowest static-pressure rating in the CLOUDLINE range and a 100 mm carbon filter is a real restriction. Keep the duct run short and straight and you'll be fine for odour control on a small space. If filtration is the main job and the run is long or bendy, size up rather than pushing this one.
Is 26 dBA actually quiet?
Yes — 26 dBA at rated speed is quiet enough to sit in a lounge-room AV cabinet without being noticed, and it is the lowest figure in the range. That is the number at the rated speed, not at level 10; wound right up it becomes audible, as any fan does. A silencer and lined ducting help if the fan is in the same room you sleep in.
Can I add a smart controller later, or do I have to buy the T4?
You can add one later. The fan is UIS compatible, so a Controller 69 Pro or Controller AI+ plugs straight into it in place of the 10-speed dial. Buying the T4 up front is cheaper than buying the S4 and a controller separately, so the decision is worth making now if you already know you want automation — but you are not locked out of it.
Can I use it for subfloor, attic or bathroom ventilation rather than growing, and which size suits a bathroom?
Yes, and plenty of the S4s we ship go to exactly those jobs. It's IP44-rated and mounts horizontally or vertically. For bathroom exhaust, read the installation requirements above — it must be part of a properly designed ducted system.
Most people use the 150 mm for a bathroom, or the 100 mm for smaller rooms such as ensuites and toilets. The larger the fan, the quieter it is for the same airflow, because it can run slower. What suits your job also depends on the space in the ceiling, the duct route and how much noise you can live with, so if you are unsure, send us the details and we will help.
How does the airflow compare with a ceiling or bathroom exhaust fan?
Installers rate exhaust fans in m³/h or L/s. The S4 moves up to 384 m³/h (107 L/s) at full speed. For comparison, the National Construction Code minimum for a bathroom or toilet is 25 L/s (90 m³/h), and 40 L/s (144 m³/h) for a kitchen or laundry, discharged outdoors rather than into the roof space. Real airflow drops with every metre of duct, bend and grille, which is where the 223 Pa static pressure rating matters. Check the requirements for your job with your installer.
Is this a genuine AC Infinity unit with Australian warranty?
Yes. Quick Bloom Lights is the official Australian importer and distributor for AC Infinity. Every unit ships with an Australian three-pin plug, SAA certification, and a two-year warranty handled here in Sydney — no shipping units overseas and no dealing with an offshore seller if something goes wrong.