This calculator provides the means for the user to generate their own refrigerant pressure-temperature (P-T) or temperature-pressure (T-P) charts for most desired refrigerants. Both English and metric units of measurement are supported as well as common units of measure for vacuum pressures. Altitude pressure adjustment to gauge pressure is also supported.

The app allows the user to select from a list of units of measurement for vacuum pressures. These vacuum units are common with either English or metric HVACR manifold gauges. These units of measurement are absolute, and provide improved precision for the vacuum pressure range compared to either psig or bar(g). By convention, these values are "reversed". The zero value corresponds to atmospheric pressure, the same as the gauge scale. The maximum value corresponds to the maximum vacuum pressure, or lowest pressure in absolute terms. This the way the vacuum pressure values are displayed on a manifold gauge. By default, the app uses the same units of measurement for vacuum pressure as the selected gauge pressure scale. In this case, the vacuum pressures are displayed simply as negative numbers. All vacuum pressure values will be displayed in a bold blue font.

If the user in interested in using vacuum pressure values in a pressure-temperature (P-T) chart, values for input pressure must be entered as negative numbers in the selected units of measurement for gauge pressure. The app will then convert to appropriate values in the selected units of measurement for vacuum pressure.

One interesting feature of the app is the user can select "smart intervals" for the chart. This option will have the app determine optimal pressure or temperature intervals for the selected refrigerant based on the range of values and number of data points specified. The app will adjust intervals in an appropriate manner to account for the fact the pressure and temperature relationship is not linear. Note that the the app uses the number of data points specified in its interval adjustment algorithm, and the actual number displayed on the Results page will likely be different.

A sample Word file may be downloaded from the following link: P-T Chart Word template. This template may be used to assist in designing a P-T style chart for printing. The template is in Word 2013 format and may be opened in any version of Word 2007 or later. Output can be easily copied and pasted from the Results page to a Word document. On a Windows PC, highlight the values of interest and use Ctrl-C and Ctrl-V to copy and paste them respectively. Consider first copying and pasting Results page output to a temporary Excel file. This will allow the user to arrange the values to their liking before copying and pasting to a Word document.