|PerformCalc™ - HVAC&R Performance Test Updated 4/12/17||Provide inputs in the blue boxes, other inputs optional.|
To find a systems current steady state capacity:
To calculate Btu's of dry air, provide dry bulb temperatures only, for moist air, add the return air humidity. To calculate changes in humidity include the supply air humidity as well. Provide airflow to convert Btu's per pound to Btu's per hour and to also calculate air conditioning and heat pump efficiencies when voltage and amperage are also entered.
To find the airflow of an air-handler or an electric furnace:
You can calculate CFM from the btu output of an electric heater and/or bower motor (airflow input must be blank), Provide dry bulb temperatures, volts and amps of the indoor air-handling unit. Add return air humidly for slightly higher accuracy. Assure the "Calculate Airflow from Electric Heat or Blower Motor Temperature Rise" check box is checked and "Electricity" from the "Heating Fuel" drop down list is selected.
With a well sealed unit and duct connections, matched thermometers & accurate static pressure measurements you can calculate CFM from the Temperature Rise of the blower motor only (must be in the airstream). All electrical power input is converted to sensible heat or a change in pressure (ultimately all of it is measurable energy).
This performance calculator takes a snapshot of the systems current operation and assumes steady state operation for one hour. 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.
Humidity inputs, if not entered will calculate the air as dry, or with the supply air at the same moisture content as the return air when possible.
This calculator illustrates the difference when using standard air factors such as, 1.08, 4.5, and 0.68, (0.075 lbda/ft³ and 0.24 Btu/ft³·°F) instead of the actual conditions.
For fossil fuel heating calculations; if the calculated input capacity at the efficiency percentage provided does not approximately match the rated input capacity on the nameplate, then the furnace may not be performing as rated. This could be due to altitude, nozzle size and/or fuel pressure changes.
Natural Gas https://www.eia.gov/outlooks/steo/tables/pdf/5btab.pdf To convert Dollars per Thousand Cubic Feet ($/Mcf) to Dollars per Hundred Cubic Feet ($/Ccf) , divide by 10. To convert Ccf to Therm multiply by 1.0002387672212
Heating Oil & Propane http://126.96.36.199/petroleum/heatingoilpropane/
Distillate Fuel Oil & Propane http://www.eia.gov/totalenergy/data/monthly/pdf/sec13_1.pdf To convert Million Btu per Barrel to Btu per Gallon, divide by 0.000042