To understand psychrometrics, we need to be able to quantify air: its weight, humidity, pressure, etc. We can do a better job as technicians if we figure out the air’s content and see how it relates to the CFM and overall unit performance. That way, we can have a more holistic view of HVAC performance instead of just focusing on adding or recovering refrigerant to improve performance.

The psychrometrics chart helps us understand the conditions of the air based on quantities like water vapor, dew point, and more. The chart may intimidate techs, but it contains a wealth of information that can help technicians understand the air and the customer’s comfort better.

Basic psychrometrics can also help us grasp why furnaces don’t actually dry out air; they pull the moisture out of the air and pull it back in, so the absolute humidity stays close to the same. However, we commonly add humidifiers because the relative humidity drops with the temperature rise.

Eugene and Bryan also discuss:

• How air filters and blower motors interact with the air
• Things that affect the weight of air per cubic foot
• Humidifying air and its effect on the density of air
• High-pressure air moving to an area of lower pressure
• How latent heat works
• Pressure and the atmosphere
• Absolute vs. relative humidity

Learn about ESCO’s e-learning network at hvacr.elearn.network/ and “Psychrometrics Without Tears” at https://www.escogroup.org/training/ps…. ESCO also holds the HVAC Excellence Conference; learn more about that at https://www.escogroup.org/hvac/nhetc/….