HVAC Math Handbook: A Complete Guide to Load Calculations, Formulas, Unit Conversions, Airflow, and Practice Problems for Heating, Cooling, & Refrigeration Technicians

Four hundred cubic feet per minute per ton. A constant of 1.08 on the air side and 500 on the water side. Every heating, cooling, and refrigeration technician runs on numbers like these — and almost nobody can say where they come from, or when they stop being true.

That is because the trade's arithmetic is scattered: a sizing table here, a manufacturer's bulletin there, a slide chart on the back of a pressure-temperature card, a rule of thumb passed down a shop until nobody remembers what it was derived from. It works until the job leaves standard conditions — a duct run at altitude, an air handler in a hundred-and-forty-degree attic, a nameplate that mixes two measurement systems. The technician who has only memorized the number is stuck the moment the table runs out. And a wrong number in this trade is never an abstraction: it is an oversized furnace, a starved coil, a callback, a compressor that dies young.

This handbook was built to close that gap. It gathers the calculations a technician actually performs — on a service call, at a start-up, during a replacement estimate — and works each one through from the physical relationship that produces it to the number written on the invoice. Where a shortcut exists, the derivation that justifies it comes first, along with the conditions under which it fails.

What you will take from it:

• One conversion method that handles any unit conversion, including ones you have never seen before
• The sensible, latent, and total heat equations — and how to correct their constants when conditions are not standard
• A complete heat loss and heat gain calculation, from design conditions to room-by-room equipment selection
• Airflow verified by duct traverse and by temperature rise, the fan laws, and duct sizing by friction loss against available static pressure
• The refrigeration cycle read from two gauges and two thermometers — superheat, subcooling, compression ratio, and charge limits for the newer mildly flammable refrigerants
• Combustion arithmetic: clocking a meter, input, output, efficiency, temperature rise, and gas pipe sizing
• Pump curves, glycol corrections, and expansion tanks on the water side; amperage, voltage drop, and power factor on the electrical side — through operating cost and simple payback.

The apparatus is built for learning and for the truck: 141 fully worked examples showing the equation, the substitution, and the units at every step; more than 400 end-of-chapter practice problems, each answered with a complete worked solution; a master conversion appendix with exact factors; every equation in the book collected in one place; reference data tables; a field quick reference; and a glossary of roughly 190 terms. Chapters are self-contained enough to open anywhere and cross-referenced enough to read straight through. Units follow United States practice, with an appendix for working any calculation in the units used across the English-speaking world.

It is written for the apprentice meeting this material for the first time, the trade-school or community-college student with an exam ahead, the working technician tired of trusting numbers he cannot check, and the estimator or service manager who checks them.

Stop working from numbers you cannot verify. Get your copy and start carrying the arithmetic that holds up when the table runs out.

The number on the calculator is only useful if it represents the system in front of you.

HVAC Math Handbook brings together the mathematics used across heating, ventilation, air conditioning, and refrigeration work and develops it from basic technician arithmetic through applied field calculations.

Beginning with fractions, decimals, rounding, formula rearrangement, unit conversion, geometry, and estimation, the book builds toward heat transfer, pressure, psychrometrics, load calculation, airflow, fan laws, duct sizing, refrigeration, combustion, hydronics, electrical calculations, efficiency ratings, and operating cost.

That same approach is applied throughout the book, allowing the reader to understand when familiar shortcuts are valid and when conditions require something different.

Worked examples make the calculation process visible from beginning to end. Equations are selected and rearranged, values are substituted, units are carried through, intermediate results are shown, and final answers are checked against reasonable field values.

Practice problems close each chapter, followed by complete worked solutions that reveal not just the correct number but the route used to reach it.

The coverage extends from everyday service calculations to psychrometric analysis, whole-house loads, airflow verification, duct friction, superheat and subcooling, A2L refrigerant charge limits, gas input, combustion analysis, pump and hydronic calculations, conductor sizing, SEER2 and EER2 relationships, and operating-cost comparisons.

The A2L material, for example, does not stop at naming the newer refrigerants. It works through the relationship between refrigerant charge, release height, and minimum room area and emphasizes the need to follow equipment-specific installation instructions.

Designed as both a learning resource and a working reference, HVAC Math Handbook is for readers who want more than formulas to memorize. It is for anyone who wants to understand the calculation well enough to recognize when a number is reasonable, when an assumption has failed, and what to measure next.