How To Read A Psychrometric Chart _verified_

Once you understand how to navigate it, you can predict how air will behave when it is heated, cooled, or humidified. Here is your comprehensive guide on how to read and use a psychrometric chart. 1. The Anatomy of the Chart

Maintain a laminated copy of a sea-level psychrometric chart at every HVAC workstation. Practice plotting three states daily for one week to build fluency.

A psychrometric chart is defined by five distinct lines. Learning to distinguish them is the key to mastery. how to read a psychrometric chart

These are the curved lines that mimic the shape of the saturation curve but sit further to the right. They are usually labeled as 10%, 20%, 30%, etc.

The chart is based on three primary factors: , moisture content , and energy . Before you can plot a point, you need to recognize the seven distinct scales that crisscross the graph. A. Dry-Bulb Temperature (DB) The Lines: Straight vertical lines. The Scale: Found along the bottom horizontal axis. Once you understand how to navigate it, you

| Line/Curve | Symbol | Shape | Location on Chart | | :--- | :--- | :--- | :--- | | Dry Bulb Temperature | DBT | Vertical, straight lines | X-axis (bottom) | | Humidity Ratio | W or HR | Horizontal, straight lines | Y-axis (right side) | | Saturation Curve | 100% RH | Curved line (left edge to top) | Upper left boundary | | Relative Humidity | RH | Curved, concave lines | Between saturation and dry region | | Wet Bulb Temperature | WBT | Diagonal, straight lines | Slanting down to the right | | Specific Volume | v | Diagonal, straight lines | Similar to WBT but steeper | | Enthalpy | h | Diagonal, straight lines | Parallel to WBT lines |

| Action | Procedure | Result | | :--- | :--- | :--- | | | Find 80°F on bottom axis. Draw line up. | Vertical line at 80. | | 2. Plot WBT | Find 67°F on saturation curve. Follow diagonal down-right. | Diagonal line through 80°F vertical. | | 3. Intersection | Mark the crossing point. | State Point "A". | | 4. Read RH | See which RH curve passes through Point A. | 50% RH | | 5. Read HR | Move right from Point A to Y-axis. | 0.011 lb water / lb dry air | | 6. Read DPT | Move left from Point A to 100% RH curve; drop down. | 60°F | | 7. Read Enthalpy | Follow diagonal from Point A to left scale. | 31.4 BTU/lb | The Anatomy of the Chart Maintain a laminated

Dry Bulb = 80°F, Wet Bulb = 67°F.