Combustion Efficiency Tests: A Deeper Dive

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Technicians perform combustion efficiency tests as part of routine heating system maintenance to measure how well the system converts fuel into heat. These tests help inform the technician whether they’ve set up the burner right. Further, they boost system efficiency, which helps customers lower their energy costs.


To completely burn fuel, a certain amount of air must be present. With the right amount of excess air, the heating equipment will keep heat loss to a minimum, and combustion efficiency will improve. However, if…


  • There’s too little air, it can lead to smoke, soot and carbon monoxide
  • There’s too much air, it can lead to poor efficiency and heat loss

That’s why it’s important to get it just right. To do so, the technician can adjust a few variables – combustion air, fuel pressure and draft. They often use digital instruments that automatically calculate efficiency as the test goes. Alternatively, manual instruments can be used, but they’re more time consuming and often less reliable.


A standard procedure covers a few areas:


    • Testing the temperature of the combustion gases leaving the system, or the stack temperature. This indicates how much energy didn’t transfer from fuel to heat.
    • Testing for draft through the burner, heating unit and vent system.
    • Testing for smoke in the flue gases. Keeping smoke to a minimum is essential for the system to operate at maximum efficiency.


  • Testing the temperature of the flue gases.
  • Calculating the efficiency of the system.



If your heating system’s combustion efficiency is lower than 78, you may want to upgrade to a higher-efficiency system – doing so can help you lower your heating costs.


To learn more, contact Fsi Oil and Propane today.