Trade Math & Applied Science
Unit conversions, temperature scales, pressure calculations, area and perimeter, fractions, and applied physics for HVAC technicians.
- Convert between Fahrenheit and Celsius temperature scales
- Calculate pressure in water column height and psig
- Convert BTU to tonnes of refrigeration
- Solve area, perimeter, and volume problems for HVAC applications
- Apply fraction and decimal math to sheet metal and piping measurements
Lesson 1
Temperature & Pressure Conversions
Temperature Scales in HVAC
HVAC technicians work constantly with two temperature scales: Fahrenheit and Celsius. The Red Seal exam tests your ability to convert between them quickly and accurately.
The conversion formulas are:
- Celsius to Fahrenheit: F = (C x 9/5) + 32
- Fahrenheit to Celsius: C = (F - 32) x 5/9
A critical fact for the exam: -40 degrees is the point where Fahrenheit and Celsius scales intersect. When asked to find Celsius for -40 F, the answer is -40 C. This is a commonly tested trick question.
Another frequently tested conversion: 41 F equals 5 C. Using the formula: (41 - 32) x 5/9 = 9 x 5/9 = 5 C. This is a standard refrigeration temperature for walk-in coolers.
Pressure Conversions
Pressure in HVAC is measured in several units. The most important conversion for the exam is between psig and water column height:
0.433 psig equals 1 foot of water column. This means a column of water 1 foot tall exerts a pressure of 0.433 psig at its base. This relationship comes from the formula P = rho x g x H (pressure equals density times gravity times height).
Remember This Number
0.433 psig = 1 foot of water column. If the exam gives you a circulating pump pressure differential of 21.65 psi, divide by 0.433 to get 50 feet of head.
Memorize: 41 F = 5 C, -40 F = -40 C, and 0.433 psig = 1 foot of water column. These three conversions appear repeatedly on the Red Seal exam.