For large, open or semi-open spaces such as factories, warehouses and halls, a duct cooler gives far more cooling for the money than air conditioning, and it brings in fresh air. AC is the better choice for small, sealed rooms, very humid conditions, or where temperature and humidity must be held to a set point.
How each one cools
A duct cooler pulls outside air through wet cellulose pads. Water evaporating from the pads takes heat out of the air, and a fan pushes the cooled, fresh air into the building through ducts. It uses a fan motor and a small water pump. Nothing is sealed and no refrigerant is involved.
An air conditioner uses a compressor and refrigerant to take heat out of the room air and dump it outside. It cools the same air again and again in a closed room.
Side by side
| Duct cooler | Air conditioning | |
|---|---|---|
| Cooling method | Evaporation | Refrigerant cycle |
| Air | 100% fresh outside air | Recirculated room air |
| Doors and windows | Should be partly open | Must be closed |
| Power for a factory floor | 1.1 to 4.5 kW per 1,000 to 3,000 sq ft | Many times higher for the same area |
| Humidity | Adds moisture | Removes moisture |
| Works best | Hot, dry to moderately humid weather | Any weather, including very humid |
| Installation | Simple ducting, water and power | Refrigerant piping, insulation, sealed building |
| Maintenance | Pads, pump, water | Gas, compressor, filters, coils |
Running cost
A 30,000 CMH duct cooler covers up to about 2,000 sq ft on a 3 kW motor. Cooling the same open shed with AC would need far more power, and the open doors and hot metal roof of a typical shed would waste much of it.
Comfort
A duct cooler lowers the air temperature and keeps air moving, which together make a big difference to how people feel. It also replaces stale air, fumes and odours with fresh air, which AC does not.
In very humid weather, such as the peak of the monsoon on the coast, evaporative cooling cools less because the air cannot take up much more water. The airflow still helps, and HVLS fans add to it.
When to choose a duct cooler
- Factory floors, workshops and warehouses
- Spaces with doors that stay open
- Kitchens, canteens and halls
- Sites where running cost matters
- Places where fresh air is wanted, to dilute fumes or heat
When to choose AC
- Offices, control rooms and server rooms
- Clean rooms and labs needing set humidity
- Spaces that can be fully sealed
- Very humid locations where the main complaint is stickiness
The common combination
Many factories use both: AC for offices and control rooms, duct coolers on the shop floor, and exhaust fans to remove hot air. See duct air coolers or read how many coolers your factory needs.
Frequently asked questions
Is a duct cooler cheaper to run than AC?
Yes, by a wide margin for large open spaces: a duct cooler uses a fan motor of 1.1 to 4.5 kW and a small pump, with no compressor.
Does a duct cooler work in humid weather?
It cools less when the air is very humid, but still brings in fresh, moving air. It works best in hot, dry to moderately humid weather.
Can a duct cooler replace AC in an office?
For sealed offices that need set temperature and humidity, AC is the better choice. Duct coolers suit open, ventilated spaces.