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HVAC Resources for Professionals  

HVAC Calculators

It is impossible to make a calculator that is both simple and concise while being customizable with state of the art accuracy. With many simple HVAC calculators already available, I choose to emphasize accuracy and customization over simplicity.

These calculators are best viewed with a Chrome Desktop browser. Sorry some are not mobile or IE friendly.

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PerformCalc - HVAC Performance Calculator : Based on the Psychrometric and Coil Performance Calculator, this calculator takes a snapshot of the systems current operation and calculates the performance, efficiency and cost.



Wayne's Air Conditioner Analyzer  A.K.A. "Wayne's Brain": A calculator that troubleshoots the refrigeration and air flow of an air conditioner by entering the operating temperatures and pressures. Click "Analyze" to see the results. Find out what is in or out of range. Scroll down for a diagnosis with causes and/or remedies.


  Wayne's Brain

Psychrometric and Coil Performance Calculator:  Psychrometric data is not only useful for commercial design, Technicians can also benefit from knowing exactly how a system is performing based on the actual entering and leaving conditions. You can download and print psychrometric charts from Coolerado Cooling.



Residential Air Duct Sizer and Velocity Calculator:  This free ductulator calculates the exact duct size (round and rectangular) for the given friction rate, duct type, and amount of airflow.  It will automatically adjust the size to keep from exceeding the maximum Manual D velocities for residential duct systems. Click for a Demonstration




All Duct Calculator:  An inclusive air duct calculator for diameter, velocity, CFM, and pressure drop of various types of duct. It will also determine round duct equivalents for rectangle, flat oval, and elliptical (flattened round) duct.

Duct roughness and air properties are adjustable and includes a metric option.


Friction Rate Calculator:  A calculating web form for use with the Manual D procedure to determine the friction rate for sizing a residential duct system.



  Friction Rate Calculator

Transfer Grille Size Calculator:  With the doors closed, the amount of airflow supplied to a room is limited by the amount that will exit from the room. The room becomes pressurized. An over pressurized room will expel conditioned air to the outside, attic, or crawlspace. Use this calculator to determine the minimum effective transfer grille size required to limit the pressure difference between the room and the outside to a maximum of 0.012"wc.  Read more on transfer grilles here; Building Science Corporation.


  Transfer Grille Size Calculator

Air Balancing Calculator:  A calculating web form for recording and calculating the Stepwise air balancing process. Enter the outlet description (optional) and the design airflow, click "Calculate" to display the 10% range. Enter the measured value of each outlet and it will tell you the percentage you are over or under, if within 10% it displays "OK".

Balancing a "Rule of Thumb" designed duct system is difficult if not impossible. Balancing is easy when the branch ducts are the size determined by the Manuals J and D procedures. Then only small changes in damper position are required. Typically less than 25%.

  Air Balancing Calculator
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