Arkansas HVACR NewsMagazine May 2026

HVACR NewsMagazine May 2026

Tech News

Understand Dew Point and Absolute Moisture,

The Right Side of the Psych Chart

These are both cases where a basic understanding of a psychrometric diagram can help a technician. While some of the elements on the chart are represented by curved or slanted lines, dew point temperature and humidity ratio/absolute moisture content values are just straight lines horizontally across the chart.

L et's first state the obvious. Most techs are intimidated by psychrometric charts and Mollier diagrams. We JUST ARE. While there are some pretty complicated formulas that back up these diagrams, using them isn't that big of a deal once you understand the different elements and then focus on one at a time. Dew point is one example of a very useful measurement to understand, design for, and test for in an HVAC/R system. Take an evaporator coil; do you know how to calculate the exact temperature at which that evaporator coil will start to condense moisture? Can you tell the exact temperature at which a surface inside a space will start to condensate and possibly grow mold? BUT WHY DO YOU CARE?