1. Calculate the ‘delta T’, the change in temperature, between the inlet and outlet water. Measuring the ‘delta T’ requires a thermocouple or thermometer. Check the water temperature of the water inlet line and the water outlet line, and subtract the numbers to compute how much heat the equipment is adding to the water.
2. Rate of flow in gallons per minute (GPM). To measure the flow rate of the water place a flow meter on the outlet line of your equipment. If one is not available, simply measure the time it takes for the outlet flow to fill a five gallon bucket, and then compute your gallons per minute (GPM) of flow (see calculator below).
3. Now that you have these two figures, calculate how many BTU’s (British Thermal Units) your equipment puts off.

BTU/ hour = 500 x GPM x Temperature Difference (delta T)

Repeat this for all the equipment you have, and add up the total BTUs. Now that you have the BTUs, compute the total tons of cooling you need from a chiller. For example, 1 Ton of cooling is 12,000 BTU/hour s

# Tons = (BTU/hr) / (12,000)

This is the size unit you should need. There may be other circumstances, like planning for expansion, high ambient temperatures, etc that could lead you to buy a different size unit. Feel free to contact us to help review your calculations

Labs, Plastics, Lasers, Semiconductor, Medical, Pharmaceutical, Extraction, Chemical, the list could go on and on.  What all of these industries have in common is they all require a chiller at some point in the process.  Determining the size of the chiller required is as simple as following a formula.  As long as you have a few facts, it may be done without being an expert.  However, if you’re unsure, please do not be afraid to contact us, we’d love to assist you.

How to Size a Chiller

There is a single and easy to follow formula for determining the size of chiller you require. However, there are a few factors you must know before you begin:

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

General sizing formula:

1. Calculate Temperature Differential (ΔT°F) ΔT°F = Incoming Water Temperature (°F) – Required Chill Water Temperature
2. Calculate BTU/hr. BTU/hr. = Gallons per hr x 8.33 x ΔT°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 10 GPM from 72°F to 58°F?

1. ΔT°F = 72°F – 58°F = 14°F
2. BTU/hr. = 10 gpm x 60 x 8.33 x 14°F = 69,972 BTU/hr.
3. Ton Capacity = 69,972 BTU/hr. ÷ 12,000 = 5.831 Tons
4. Oversize the chiller = 5.831 x 1.2 = 6.9972
5. A 6.9972 or 7-Ton chiller is required