Tech Note: What is Combustion Efficiency?

What is Combustion Efficiency?

In Tech / Application Notesby Bacharach

Combustion efficiency is the calculation / measurement, in percentage, of how well your equipment is burning a specific fuel. Complete combustion efficiency (100%) would extract all the energy available in the fuel. However, 100% combustion efficiency is not realistically achievable. Various combustion processes produce combustion efficiencies from 0% to 95+%. Combustion efficiency calculations assume complete fuel combustion and are based on three factors:

  1. The chemistry of the fuel.
  2. The net temperature of the stack gases
  3. The percentage of oxygen or CO2 by volume after combustion.

If your calculation shows that your equipment is losing 25% of the heating value of the fuel through stack losses, your equipment is running at 75% efficiency.

Combustion Processes and Their Combustion Efficiency Ranges
Combustion Process Efficiency Range
Residential Fireplace 10-30%
Space Heater 50-82%
Commercial Gas Boiler 70-82%
Residential Gas Furnace with Atmospheric Burner “Low Efficiency” 70-82%
Oil Burner Heating System 73-85%
Induced Draft Furnace “Medium Efficiency” 74-82%
Boiler with Gas-powered Burner 75-83%
Condensing Furnace (Gas & Oil) “High Efficiency” 75-90+%

What is Measured to Determine Combustion Efficiency?

One only needs to measure gas concentration (O2 or CO2) and temperature to determine combustion efficiency. Although other gases (NOx, CO, SO2) do not significantly effect combustion efficiency, these gases are an important safety and environmental concerns.

Determine Combustion Efficiency

Bacharach's Fyrite InTech is the perfect tool for entry-level and residential technicians who need to ensure safe operating conditions and determine combustion efficiency.