'Calculate with Standard Air' should be unchecked.Īn example of a 'Standard Air Specific' ton of air conditioning can be calculated with, 80° dry bulb, and 67° wet bulb as the entering air, 60° dry bulb and 86.65% relative humidity as the leaving air, 400 entering or leaving standard CFM for air flow, with the 'Calculate with Standard Air' option checked. 'Enhancement Factor' and 'Compressibility Factor' options should be checked. 'Calculate with Standard Air' should be unchecked.Īn example of an actual 'Dry Air Specific' ton of air conditioning can be calculated with, 80° dry bulb, and 51.2% relative humidity as the entering air, 61° dry bulb and 82.1% relative humidity as the leaving air, 0 feet for altitude, 400 entering or leaving standard CFM for air flow, -0.25'wc (negative) entering static and 0.11'wc leaving static pressure with the 'Moist Air Specific 'option unchecked. Conversion factors are listed in ASHRAE RP-1485.įor an example of an actual 'Moist Air Specific' ton of air conditioning, input 80° dry bulb, with 51.2% relative humidity as the entering air, 61° dry bulb with 79.7% relative humidity as the leaving air, 0 feet for altitude, 400 Entering actual CFM for air flow, 0.25'wc entering and 0.1'wc leaving static pressure with the 'Moist Air Specific', 'Enhancement Factor' and 'Compressibility Factor' options checked. The results are converted back to IP units for display. Temperature, humidity and pressure inputs in are converted to SI values for calculations of volume, density and enthalpy.

Other properties are calculated using equations and Tables from ASHRAE 2009 Fundamentals and 2008 HVAC Systems and Equipment.Įquation of State is (P The Wet Bulb, Dew Point and Apparatus Dew Point are iterated using a curve fitted Enhancement Factor. The Volume, Density, Enthalpy, Compression Factor and Enhancement Factors. This Psychrometric Calculator uses formulae from ASHRAE RP-1485 'Thermodynamic Properties of Real Moist Air,ĭry Air, Steam, Water, and Ice' by S.

Ashrae psychrometric enthalpy