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How To Size A Chiller

The appropriate sizing of Chillers is an essential requirement for operational efficiency. There are a few parameters that are required for this simple calculation. They include:

  • Inlet Water Temperature
  • Exit Water Temperature
  • Flow Rate

If you are looking to size a chiller, here are the steps to follow:

Step I
  • Calculate Temperature Differential (ΔT°F)
  • ΔT°F = Inlet Water Temperature (°F) – Exit Water Temperature (°F)
Step II
  • Calculate BTU/hr
  • BTU/hr. = Gallons per hour x 8.33 x ΔT°F
Step III
  • Calculate tonnage of cooling capacity
  • Tons = BTU/hr. ÷ 12,000
Step IV
  • Apply an oversize factor of 20%
  • Ideal Size in Tons = Tons x 1.2

Let’s use the 4-step calculation above to estimate the size of chiller required to cool 20 GPM from 95°F to 45°F.

I – ΔT°F = 95°F – 45°F = 50°F

II – BTU/hr. = 20 gpm x 60 mins/hr x 8.33 x 50°F = 499,800 BTU/hr.

III – Ton Capacity = 69,972 BTU/hr. ÷ 12,000 = 41.65 Tons

IV – Oversize the chiller = 41.65 x 1.2 = 49.98

A 50-Ton Chiller is required for this application.

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