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Every so often, it seems like HVAC technicians have to be experts in everything. You’re not only skilled at making tiny boxes pump out warm or cool air, but you also run the numbers like a mathematician.

While homeowners may think that all of your knowledge boils down to “throw up some ductwork and replace the broken part,” it’s not that simple. The truth is that very specific formulas govern good HVAC work, driving the decisions technicians make every day.

Of course, no tech has each formula memorized perfectly.  In fact, some may not even understand how those formulas function.


So to that end, here is a compiled list of HVAC Formulas that are typically needed and regularly used.

HVAC Formulas

An HVAC load calculation involves determining the number of BTUs (thermal units) required to adequately heat and cool a given space. BTUs measure the amount of heat needed to raise the temperature of one pound of water by one degree Fahrenheit. The size of a room measured in footage (sq ft) determines the capacity, in BTUs per hour (BTU/hr) which indicates how much heating or cooling is necessary to achieve the desired temperature.


Manual J Load Calculation

Professionals rely on the Manual J Residential Calculation, developed by the Air Conditioning Contractors of America (ACCA) for accurate HVAC unit sizing. Although this calculation typically requires time-consuming computer programs that can be expensive contractors often resort to using a rule-of-thumb approach with a BTU calculator for field technicians. By ensuring an HVAC unit is properly sized users can achieve their desired temperature without wasting energy. 

HVAC Formulas
HVAC Formulas
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