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A Beginners Guide to Using Air Conditioner Performance Graphs


Performance graphs are a useful tool when evaluating the suitability of an enclosure air conditioner, They help to verify that the correct unit with the proper cooling capacity has been selected. Utilizing basic known criteria, these graphs illustrate a particular air conditioner’s performance at different operating temperatures, and therefore, help in selecting the right size and capacity required. At first glance,they can seem a bit overwhelming. However, understanding some simple data points of how they are formulated can go a long way to understanding and using them. 

Let’s look at an example, using the graph below. (Different air conditioners will each have thier own individual performance graphs). Follow the instructions to determine the cooling capacity required for a specific application.


  1. Locate 110⁰F Ambient Temperature at the bottom of the chart.
  2. Follow the vertical line up until it intersects with the diagonal blue line @ 100⁰F maximum enclosure air temperature curve.
  3. Follow the horizontal line to identify the actual cooling capacity that the unit will deliver at these conditions.
  4. In this case, this unit will deliver approximately 8,000 BTU/H. If the unit’s capacity under this condition was below 8,000 BTU/H, select another model with more capacity. If the capacity was significantly above the 8,000 BTU/H requirements, a smaller model should be selected.

Note: Operating units below their optimum capacity (the shaded blue area) is not recommended and may result in icing or damage to the compressor. One should consider using a larger unit in this situation.

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Summary of our example :

  • The maximum ambient temperature is 110⁰F. 
  • The maximum enclosure air temperature is 100⁰F.
  • The maximum air conditioner capacity is 8,000 BTU/H.

Determine the required operating voltage and NEMA style to further narrow your choices. 


Topics: Cooling basics, Air Conditioners

Steve Coulton

Written by Steve Coulton

Steve is the Sales and Marketing Manager at Kooltronic