PerformCalc™ - Heating & Cooling System Performance Calculator version 1.2
Enter and adjust the values in the blue boxes, Click the "Update" button for the results.
Location   sCFM   Heating Fuel Temperature(s) needed    
     
0 ft, 14.696 psia, Constants: Sen=1.08 Lat=0.68 Tot=4.5    
   
       
Return Air °F   Supply Air °F        
Dry Bulb   Wet Bulb Dry Bulb   Wet Bulb        
             
Enter DB Enter DB      
23 - 149 °F 32 - 174 °F        
     
Air Handler   Condenser      
Volts   Amps   Volts   Amps    
           
     
     
Cost of fuel ($) Btu per fuel unit    
$/kW Elec 3.41214 Btu/Watt      
$/gal OIL   Btu/gal        
$/gal LP   Btu/gal      
$/thrm NG 100,000 Btu/therm    
       
     

 

To find a systems output capacity:

To calculate Btu's per pound of dry air (btu/lb), provide "Return Air" and "Supply Air" dry bulb temperatures, for Btu's per pound of moist air, add the return air wet bulb temperature. To calculate changes in humidity include the supply air wet bulb temperature as well. Provide the supply airflow volume in cubic feet per minute sCFM to convert Btu's per pound of air to Btu's per hour and to calculate air conditioning and heat pump efficiencies.

 

To find the airflow of an air handler with electric strip heat, or electric furnace:
To calculate CFM from the btu output of electric resistance elements (CFM input must be blank), select "Electricity" from the "Heating Fuel" drop down list, provide "Return Air" and "Supply Air" dry bulb temperatures, and volts and amps of the resistance heaters.
 
This performance calculator takes a snapshot of the systems current operation. Capacity, efficiency, fuel use and cost are based on the single set of inputs. It can be used for comparative purposes like before and after a repair for example.
Wet bulb temperatures, if not entered are calculated for dry air and/or equal grains of moisture when possible.
This calculator illustrates the difference when using standard density factors such as, 1.08, 4.5, and 0.68, which assume the supply air is 70°, bone dry, and at sea level. The actual density is used for calculations whenever the supply air wet bulb is entered or calculated from the return air conditions.
For fossil fuel heating calculations, If the calculated rated input capacity at the AFUE percentage provided does not approximately match the rated input capacity on the furnace nameplate, then the furnace is not be performing as rated. this is often due to nozzle size and/or oil pump pressure changes.
For more accurate results, measure voltage and amperage with the access panels in place and at the same time as the airflow measurment
The calculations of refrigerant load show a division of the true sensible and latent heat loss or gain of the air. Calculations are accurate within the limitations of the data. The calculations will not correspond to load determinations obtained from approximate density factors or constants i.e. 1.08, 4.5 & 0.68 unless the supply air is 70°F dry bulb, 0% relative humidity and 14.696 psi atmospheric pressure.