# How to Properly Size an Water Chiller

When you need to cool down a product, don’t go out and buy just any industrial chiller unit. ATO has a proven formula for finding the exact water chiller for your cooling needs.

Temperature Differential

The first step is to calculate the temperature differential, meaning the difference between the current temperature of your water and the needed temperature of your water. For example, if the water is 85°F, and you need it to be at 75°F, the temperature differential would be 10°F.

ΔT°F = Incoming Water Temperature (°F)-Required Chilled Water Temperature
Example: 85°F-75°F = 10°F

British Thermal Units per Hour

Next, calculate BTU per hour. This is important because it will help us define your cooling capacity needed later on. BTU per hour is realized by multiplying your gallons of water per hour by 8.33, then multiplying that by the temperature differential.
BTU/hr=Gallons per hr x 8.33 x ΔT°F
Example: (4 gpm x 60) x 8.33 x 10°F=19,992 BTU/hr

Cooling Capacity

Cooling capacity is the measured ability of a cooling system to remove heat. You can find this by dividing the BTU per hour by 12,000.
Tons = BTU/hr ÷ 12,000
Example: 19,992 BTU/hr ÷ 12,000=1.666 tons

Ideal Chiller Size

The final step in finding the ideal size of chiller you need is to multiply your cooling capacity by 20% and round up to the nearest whole number. The resulting number will be the ton of chiller that will best suit your business.
Ideal Size in Tons=Tons x 1.2
Example: 1.666 tons x 1.2=1.9992 tons; a 2 ton chiller is needed

A final note

Because your chiller is likely to see a range of heat loads and cooling temperatures, when sizing an industrial chiller for the highest heat load and lowest temperatures you need it to handle. And, if you’re concerned about long-term operating costs, consider a chiller with a variable-speed compresso for maximum energy efficiency in partial-load situations.