Calculators
Calculators are best viewed on a laptop or desktop screen; mobile requires zooming and panning.
A calculator that troubleshoots refrigerant and air flow issues of an air conditioner. Select the systems configuration and enter 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.
Psychrometric data is not only useful for commercial design, Technicians can benefit from knowing how a system is performing from its entering and leaving coil conditions.
This 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. View a demonstration.
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.
A calculating web form for use with the Manual D procedure to determine the friction rate for sizing a residential duct system.
Ever wondered if a systems Line Set contributed to the demise of its compressor? For residential and light commercial split systems up to 7.5 tons, this tool calculates the minimum and maximum acceptable pre-fabricated Line Set tubing sizes that will accommodate correct velocities without excessive pressure drop. Calculations assure proper oil return without the use of vapor line oil traps which reduce capacity and efficiency. Credit and thanks goes to Bruce Porter P.E. He provided me the Engineered Factors critical to performing the line size calculations.
This calculator provides notes for when "Long Line" and/or "Maximum Vertical Separation" accessories are recommended by manufactures.
With closed doors, a room can become over pressurized by the HVAC system. The room will expel conditioned air to the outside, attic, or crawlspace through every crack available. Over pressure will also reduce the airflow. How much air flows into a room is limited by the amount that will flow out. Use this calculator to determine a minimum transfer grille or jump duct size. Read more at Building Science Corporation.
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, S, and D procedures. Then only small changes in damper position are needed. Typically less than 25%.
ACCA Manuals RS,J,S,D,T & B, Air Conditioning Contractors of America. Washington, DC.
ASHRAE RP-1485, Thermodynamic Properties of Real Moist Air, Dry Air, Steam, Water, and Ice. The American Society of Heating Refrigerating and Air Conditioning Engineers.
ASHRAE Handbook 2009 Fundamentals, Chapter 32, “Duct Design" formulas 19, 20, 22, 23 through 28 and Table 1. Chapter 6, “Psychrometrics" equations 5, 6, 12, 23, 25, 28, 31, 32, 34, through 38. The American Society of Heating Refrigerating and Air Conditioning Engineers.
ASHRAE Handbook 2008 Systems and Equipment, Chapter 21, “Air-Cooling and Dehumidifying Coils" equations 37, 38, 39(b) and 40. Chapter 44, “Air-to-Air Energy Recovery" equations 5 and 6. The American Society of Heating Refrigerating and Air Conditioning Engineers.
ASHRAE Toolkit for HVAC System Energy Calculations
Thermophysical and transport properties of humid air at temperature range between 0 and 100C P.T. Tsilingiris
Ellipse Equation: Ramanujan, S. "Modular Equations and Approximations to π." Quart. J. Pure. Appl. Math. 45, 350-372, 1913-1914.