Temperature conversion is required in the HVAC field and technicians are expected to know how to use them. Manufacturers who make products for HVAC are in several different countries all around the world. Each of these countries will have their own preferred mathematical calculations and conversion metrics.

Temperature conversion is a process of using empirical information to perform a quantitative conversion from one scale of temperature to another. Empirical information is given when a quantity of thermal energy is measured in a system.

The measurement of temperature is dependent upon the zeroth law of thermodynamics that expresses the principle that if two thermodynamic systems are each in thermal equilibrium with a third, then they are in thermal equilibrium with each other. It is possible for empirical scales to not be compatible with each other. When this happens, conversions are required.

International System of Units

This system is the most widely used system of measurement in the world. For HVAC purposes the following named base units will be necessary.

°F will mean the temperature in degrees Fahrenheit

°C will mean the temperature in degrees Celsius

°K will mean the temperature in degrees Kelvin

°R will mean the temperature in degrees Rankine

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To convert from degrees Celsius to degrees Fahrenheit

Temperature in °F = (9/5 x °C) + 32

To convert from degrees Fahrenheit to degrees Celsius

Temperature in °C = 5/9 x (°F – 32)

To convert from degrees Fahrenheit to degrees Rankine(Fahrenheith Absolute)

Temperature in °R (Fa) = °F + 460

To convert from degrees Rankine to degrees Fahrenheit

Temperature in °F = °R – 460

To convert from degrees Celsius to Kelvin

K = °C +273

To convert from Kelvin to degrees Celsius

Temperature in °C = K – 273

To convert from degrees Rankine to Kelvin

Temperature in K = 5/9 °R

To convert from Kelvin to degrees Rankine

Temperature ºR = 9/5 K

Again, because of the variety of products in the world and a myriad of manufacturers, it is necessary for the competent HVACR engineer and technician to understand temperature conversion. Charts, tables, and calculators are available to assist with this matter.