Quick answer: for a normal room with a 10-foot ceiling, plan on about 3 CFM of airflow per square foot. A 2,300 CFM AUSH Blower Cooler covers up to 800 sq ft. For hot, crowded or machine-heavy spaces, plan on 5 CFM per sq ft instead, which brings the same cooler down to about 460 sq ft. Tank size does not change how much area a cooler covers; it only changes how often you refill it.
How to Work Out the CFM You Need
An evaporative cooler works by replacing the hot air in a room with cooled, moist air. What matters is how quickly it can replace all the air in the space, measured in air changes per hour:
CFM needed = floor area (sq ft) × ceiling height (ft) × air changes per hour ÷ 60
- Normal rooms (homes, offices, shops): about 17 air changes per hour, i.e. the full volume of air is replaced roughly every 3½ minutes. AUSH's 800 sq ft rating for its 2,300 CFM coolers is based on this, with a 10 ft ceiling.
- High heat load (commercial kitchens, workshops with running machines, gyms, crowded halls): about 30 air changes per hour, i.e. a full air change every 2 minutes.
If your ceiling is higher than 10 ft, scale up in proportion: a 14 ft ceiling needs 1.4 times the CFM shown below.
Room Size to CFM Chart (10 ft Ceiling)
- 300 sq ft: about 860 CFM for a normal room; about 1,500 CFM for a high heat load
- 500 sq ft: about 1,440 CFM normal; about 2,500 CFM high heat load
- 800 sq ft: about 2,300 CFM normal; about 4,000 CFM high heat load
- 1,200 sq ft: about 3,450 CFM normal; about 6,000 CFM high heat load
- 2,000 sq ft: about 5,750 CFM normal; about 10,000 CFM high heat load
- 3,000 sq ft: about 8,600 CFM normal; about 15,000 CFM high heat load
For large floors it is usually better to use two or more coolers spread across the space than one very large unit blowing from one corner.
Which AUSH Cooler Fits Which Space
- Blower Cooler (90, 130, 150 or 190 L tank), 2,300 CFM: up to 800 sq ft in a normal room, or about 460 sq ft with a high heat load. Runs on 220 V single phase.
- Industrial Duct Cooler 60 L, 2,300 CFM: up to 800 sq ft normal, about 460 sq ft high heat load. Runs on 220 V single phase.
- Industrial Duct Cooler 90 L, 6,500 CFM: up to about 2,250 sq ft normal, about 1,300 sq ft high heat load. Needs 415 V three phase.
- Industrial Duct Cooler 120 L or 150 L, 11,500 CFM: up to about 4,000 sq ft normal, about 2,300 sq ft high heat load. Needs 415 V three phase.
All four Blower Cooler models move the same 2,300 CFM, so they cool the same area. Choose the tank by how long you want the cooler to run between refills: the 190 L model suits long shifts or places where refilling is inconvenient, while the 90 L model suits a home or a small shop.
When an Air Cooler Is the Wrong Choice
Evaporative coolers cool best in hot, dry weather, which covers most of inland Maharashtra in summer. As humidity rises (during the monsoon, or in coastal cities) the air can absorb less water, so an air cooler cools less and makes the room feel sticky. We explain this, with figures for each humidity level, in why air coolers stop working in humid weather. If your space is humid for much of the year, look at AushCool, which cools with chilled-water circulation rather than evaporation.
An evaporative cooler also needs cross-ventilation. Keep a window or door open on the opposite side of the room so the warm, moist air can escape. A cooler in a sealed room quickly makes the air humid and stops cooling.
Frequently Asked Questions
Does a bigger water tank mean more cooling?
No. Cooling area depends on airflow (CFM), not tank size. A bigger tank only means fewer refills.
What size cooler do I need for a 1,000 sq ft shop?
About 2,900 CFM for a normal shop with a 10 ft ceiling. That is more than one 2,300 CFM cooler, so use either two Blower Coolers or one 6,500 CFM Industrial Duct Cooler. If the shop has cooking or machinery, plan for about 5,000 CFM.
Do I need three-phase power?
Only for the 6,500 and 11,500 CFM Industrial Duct Coolers, which run on 415 V three-phase supply. The Blower Coolers and the 60 L Duct Cooler run on a normal 220 V single-phase socket.
Can AUSH help me size a cooler for my space?
Yes. Send your floor area, ceiling height and what the space is used for through our contact page and our team will recommend a model, or a combination of models.
