Psychrometric Chart
Interactive psychrometric chart. Click anywhere to plot a state point, hover for instantaneous properties, and see whether the air falls inside the ASHRAE 55 summer comfort zone.
For Licensed & Trained HVAC Technicians Only
This checklist is intended exclusively for use by licensed, certified, and trained HVAC professionals. It is not a DIY guide and should not be used by untrained individuals to perform repairs or diagnostics. The purpose of this checklist is to help qualified technicians maintain a consistent, step-by-step workflow so that no critical step is overlooked or skipped during service.
Psychrometric Chart
Based on a barometric pressure of kPa at sea level
Click anywhere on the chart to plot state points. Hover for instantaneous properties. Use the table below to connect two points and see the process Δ.
Scroll the chart sideways to see the full plot →
Add a state point manually
No state points yet. Click on the chart or use the form above to add one.
How to read the chart
The X axis is dry-bulb temperature; the Y axis is humidity ratio (mass of water vapor per mass of dry air). The bold curve at the top-left edge is the saturation line (100% relative humidity); air can't hold any more moisture above it.
- Sky-blue curves — constant relative humidity (10% … 90%).
- Green dashed lines — constant wet-bulb temperature.
- Purple dashed lines — constant specific volume.
- Red lines — constant enthalpy.
All math uses the ASHRAE Handbook of Fundamentals (Hyland-Wexler saturation, full psychrometer equation for wet-bulb). Pressure is configurable for high-altitude work.
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