Web-Based Psychrometric Calculator


Johnson Controls, Inc. (JCI) certainly needs no introduction. They are one of the largest HVAC equipment and controls manufacturers in the world. They also do a lot more, and you can investigate it here.
Carmel Software was hired by JCI to develop a web-based javascript HVAC psychrometric calculator to aid in the selection of their residential line of HVAC equipment. The requirements were quite simple: Allow a user to input the elevation, entering dry- and wet-bulb temperatures, airflow, and total and sensible capacities in BTUh. Based upon a combination of all these inputs, the leaving air conditions and remaining entering air psychrometric properties would be instantly calculated. All calculations could occur in either English or Metric units.

Also, an additional web page was developed that allows for inputs for two different streams of air and displays results that include mixed-air and leaving air conditions.

The advantages of javascript versus server-side hosting are many. The main advantage, though, is that all code resides in the webpage that is on your computer. Therefore, every interaction that occurs is instantaneous and does not require an Internet connection. In other words, everything is taking place within your Internet browser (think Google Maps with its ability to instantaneously pan as you move your cursor), and all calculations occur locally on your machine, so the instant an input is updated, the outputs immediately update. It's almost as if you are using a native software tool like Microsoft Excel.
Below are some screenshots of the software that was released in 2016:


Standard conditioned air stream calcs with leaving air conditions and remaining entering air properties:
Metric units for single air stream:
Entering air at 5000 ft elevation with calculated leaving air conditions and remaining entering air properties:
Inputs for two air streams with calculated leaving air conditions and mixed air properties:
Metric units for two air streams:

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