How to Calculate Chiller Tonnage – Formula With that, our equation now looks like this:įurther clarifying this to incorporate fluids other than water, the equation changes even more: Since we know that there are 8.33 lbs in each gallon of water and 60 minutes in an hour, we can convert the “m” value to GPM or gallon per minute (of water). The truth is the equation for calculating a heat load remains the same no matter what the conditions. The problem is that this is only true in a perfect world and we don’t live in a perfect world. (Some manufacturers actually base their unit size/model on the compressor HP). So in other words, a 10HP chiller equals 10 tons of capacity. The Difference Between Compressor HP and Tonnage OutputĪnother common error is referring to the chiller’s compressor HP as being equivalent to the tonnage output. Using the earlier “10 tons” example, a nominal ten ton chiller at ARI conditions, may only produce 6-7 tons with the conditions just mentioned.īoth the glycol and the lower fluid temperature cause the chiller to be less efficient and the output must be derated. What’s that? You say you are using 30% ethylene glycol and operating at 35☏ leaving fluid temperature? Well, now the “nominal tons” no longer in the same ballpark as “actual tons”. You see “nominal tons” are typically calculated at ARI conditions, which is 44☏ leaving water temperature, 54☏ entering water temperature, and 95☏ ambient temperature. The actual tonnage for a (nominal) “10 ton” chiller can vary from four tons all the way up to 12 tons based on those pesky design conditions. But in real world conditions, a customer’s view of a ton of refrigeration process cooling is actually much different. One of the biggest misnomers is that a ton of cooling is simply a ton of cooling – no matter what the operating conditions. The Difference Between Nominal Tons & Actual Tonnage We hope to help clarify some of the uncertainty in this post.Īt the bottom of the post, we demonstrate how to accurately calculate process chiller loads with an example of a real life application. The customer has an idea of what size unit they are replacing but isn’t really sure how that “value” is calculated or derived. When we ask the customer what size chiller he or she needs, the answer is occasionally, “I think a 10 ton chiller?” (We use “10 ton” as an example only). Many times we will have a customer call in and request a chiller quote from us.

Chilled water tonnage calculation