HVACopediaAirflow & heating output
cfm, temperature rise, output and cooling airflow.
More airflow & ducts calculators
Static pressure & friction rateAvailable static pressure and the friction rate for duct designRound duct sizeDuct diameter from the airflow and the friction rateRound ⇄ rectangular ductEquivalent sizes with the same frictionVentilation & air changescfm for people or air changes, ACH from airflow, blower-door ACH50Fan lawsWhat happens to pressure and power when the airflow changesPsychrometricsWet-bulb, humidity, dew point, grains and enthalpy from two readings
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Calculation aids and reference figures for licensed technicians. Always follow the manufacturer’s data plate and manual for the exact model, and local codes. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Pressures are typical saturation values and change with load and airflow.