AC Infinity CLOUDLINE Pro S4

A 100 mm inline fan with a brushless EC motor, rated at 205 CFM (348 m³/h) at 28 dBA. Supplied with a wired ten-speed controller.

The CLOUDLINE Pro S4 is the smallest size in the range and the one most often sitting behind a carbon filter. At this size it is not the number on the box that decides what you get, but the resistance you put behind it.

What a carbon filter costs you in airflow

That 205 CFM figure is measured with a free outlet, so with no filter and no ducting attached. Add a carbon filter, a few metres of ducting and a bend or two, and the fan has to work against back pressure, so less air actually moves.

That back pressure is called static pressure and is expressed in pascals. The S4 keeps going up to 223 Pa, which is the point where nothing gets through at all. The closer your setup sits to that figure, the less of the rated airflow survives.

The design is built around exactly this. The impeller is a mixed-flow type with a stator blade behind the rotor, taking the spin out of the airflow and turning it into pressure. An ordinary duct fan of the same size collapses far sooner once resistance is added.

So plan with headroom. A 100 x 100 x 200 cm tent holds 2 m³ of air, so the rule of thumb of one air change per minute asks for 120 m³/h. Even if a filter and three metres of ducting cost you a third of the rated flow, this fan stays comfortably above that, and at half speed at that.

What is in the box

Along with the fan you get two duct clamps, hanging straps, mounting hardware and the wired controller. That controller has a single button and ten speeds: hold it for four seconds to switch the fan off, and the last speed is retained if the power drops out.

The motor box slides out of the mounting frame, so you can clean the impeller without disconnecting any ducting. The cap carrying the cable can be unscrewed and rotated if you hang the fan upside down, and doing so does not void the warranty.

Technical Specifications:

• Model: AI-CLS4
• Duct size: 100 mm (4 inch)
• Airflow: 205 CFM (348 m³/h)
• Noise: 28 dBA
• Static pressure: 223 Pa
• Speed: up to 2800 rpm
• Power draw: 28 W maximum, 21 W average
• Motor: brushless EC motor with PWM control
• Controller: wired, ten speeds, included
• Bearings: dual ball, 67,000 hours
• Ingress protection: IP44
• Dimensions: 17.6 x 30.3 x 18.8 cm

Frequently asked questions

Is 100 mm enough for my tent?
Work out your own space: length by width by height in metres gives the volume, and that figure times 60 is what you need per hour for one air change per minute. For tents up to roughly 120 x 120 cm this size stays well above that, filter included.

Can I move it onto a smart controller later?
Yes. The fan works with any AC Infinity UIS controller, and the supplied wired controller is then set aside. If you want that controller from the start, look at the T4.

Can it be mounted vertically?
Yes, in any orientation. The dual ball bearings allow any mounting direction.