Sizing by Application

No matter what your application, there is a single formula for determining the size of chiller you need. Before you begin, you must know three factors:

  • The incoming water temperature
  • The chill water temperature you require
  • The flow rate

General sizing formula:

  1. Calculate Temperature Differential (rT°F) rT°F = Incoming Water Temperature (°F) - Required Chill Water Temperature
  2. Calculate BTU/hr. BTU/hr. = Gallons per hr x 8.33 x rT°F
  3. Calculate tons of cooling capacity Tons = BTU/hr. ÷ 12,000
  4. Oversize the chiller by 20% Ideal Size in Tons = Tons x 1.2
  5. You have the ideal size for your needs

For example, what size chiller is required to cool 40GPM from 70°F to 58°F?

  1. rT°F = 70°F - 58°F = 12°F
  2. BTU/hr. = 40gpm x 60 x 8.33 x 12°F = 239,904 BTU/hr.
  3. Ton Capacity = 239,904 BTU/hr. ÷ 12,000 = 19.992 Tons
  4. Oversize the chiller = 19.992 x 1.2 = 23.9904
  5. A 23.9904 or 25-Ton chiller is required

There also industry specific rules of thumb for chiller sizing depending on your application: