How to size an industrial air cooler the right way

Sizing an industrial cooler is not about picking the biggest machine — it is about moving enough fresh air through the space often enough. The method is air changes per hour, and you can get a sound first estimate with a calculator and a tape measure before we ever visit.

The one idea that matters: air changes

Evaporative cooling works by continuously replacing the air in a space with cooler, fresh air. So the question is not “how many tonnes” (that is AC language) but “how many times per hour do we want to swap out all the air in this building?” That number is the air changes per hour, or ACH. Move the air through often enough and the space stays fresh and cool; too few changes and it feels stuffy no matter how large the unit.

The sizing formula

Three steps, no engineering software required:

1. Find the volume. Floor area (sq.ft) × roof or shed height (ft) = volume in cubic feet. Divide by 35.3 to convert to cubic metres.
2. Choose your air changes. For most industrial and commercial spaces we design for roughly 30 to 60 air changes per hour — the hotter the space, the heavier the machinery or the more people, the higher the figure.
3. Multiply. Volume (m³) × air changes per hour = the total air delivery you need, in CMH (cubic metres per hour). That total is what you match to units.

Required air delivery (CMH) = area (sq.ft) × height (ft) ÷ 35.3 × air changes per hour.

A worked example

Take a 4,000 sq.ft workshop with a 22 ft shed height:

• Volume = 4,000 × 22 = 88,000 cubic feet ≈ 2,490 m³.
• At 40 air changes per hour: 2,490 × 40 ≈ 1,00,000 CMH of air delivery.
• That is met by two Air-X 50K units (50,000 CMH each), or a larger number of smaller units if the layout suits spreading the airflow.

Drop the space to a gentler 30 air changes and you need about 75,000 CMH — three Air-X 25K units, or two 50K with margin. The point of the exercise is that the answer falls out of the building, not out of a price list.

Match the total to real units

Once you have a target CMH, you spread it across units so the air actually reaches the whole floor — several well-placed coolers usually beat one giant one. These are the ranges to size against:

Swipe the table sideways to see every column →

If the cooler cannot sit in the space, or the air has to travel through ducting into an enclosed or partitioned area, that is a blower job rather than an axial one:

Swipe the table sideways to see every column →

Things a calculator cannot see

The formula gets you a confident starting point. A few things still need eyes on the building: where the hot air will exhaust (cooling only works if stale air has a way out), how the floor is partitioned, where machinery dumps heat, and how the units should be positioned so no corner is starved. That is why, for anything beyond a single unit, we confirm the sizing with a free site survey before we quote.

Do it yourself, then let us check

Run your own numbers in the savings calculator — it applies exactly this method and suggests a configuration. Then send it through and we will confirm it against the real building. Sizing right the first time is the difference between a floor that feels cool and one that just feels breezy.