What Is Combustion Analysis and Why Is It Worthwhile?

By SHARON HAYCOCK, LEED AP O&M | 07/16/2012

Your HVACR service provider has recommended conducting a combustion analysis of your building.  Why should you consider it? 
One simple answer is that combustion analysis contributes to energy savings, safe boiler practices, and emission reduction.  In the life cycle cost of a boiler, the purchasing price is not the largest expense.  Fuel cost and boiler maintenance are more costly than the original purchase price of the boiler. 
So how can facility owners and managers lower the on-going cost of fuel and be green in the process?  One easy way is to improve the boiler fuel efficiency or in other words save energy.   Saving energy comes down to using less fuel.  Using less fuel means increasing boiler efficiency.  Increasing boiler efficiency means combustion analysis.

What is Combustion?

When oxygen in the air unites with a fossil fuel such as natural gas, combustion occurs.   The resulting combustion not only generates the heat needed for the boiler to perform but it also creates by-products.  These by-products may include carbon monoxied (CO), nitrogen oxides (NO, NO2), soot, and if the fuel contains sulfur, sulfur dioxide (SO2).  Released into the air or trapped within the boiler these substances are harmful to the equipment and toxic, too.  These harmful substances are the result of improperly controlled combustion.  Too little air in the combustion process produces carbon monoxide and soot.  Too-high flame temperature results in the release of nitrogen oxides.  In addition to wasting energy, a boiler that does not properly burn its fuel contributes to acid rain and can be in violation of federal, state and local government regulations.

So, what exactly is Combustion Analysis?

During the combustion analysis process, your HVACR provider collects information from the exhaust flue and in the boiler to draw a detailed picture of how well fuel is being burned within the boiler.  The list below is a general scope of an analysis. 

  • Gas concentrations
  • Gas temperatures
  • Pressures
  • Emissions
  • General safety checks

The following items may be included in the scope of an analysis: 

  • Oxygen (O 2 )
  • Carbon monoxide (CO)
  • Carbon dioxide (CO 2 )
  • Exhaust gas temperature
  • Supplied combustion air temperature
  • Draft
  • Nitric oxide (NO)
  • Nitrogen dioxide (NO 2 )
  • Sulfur dioxide (SO 2 )

How does Combustions Analysis Reduce Energy Usage?
An analysis of the information collected during combustion analysis will help in the process of “tuning” the boiler.  This process will help the unit burn fuel efficiently to reduce or eliminate noxious gases and soot.
The largest energy loss on a boiler is heat lost through the exhaust stack.  It can account for 30 to 35 percent of the fuel burned in a boiler.   Heat lost through the stack by passes its primary function, making steam or hot water.   Analyzing the exhaust gas temperature during combustion analysis can identify this issue.  It can also help in the boiler tuning process to ensure the unit burns as much fuel as possible during combustion.
So go green, analyze combustion to reduce emissions, reduce energy waste, and most importantly, be safe.

Bibliography
“Boiler Emissions Guide,” Cleaver Brooks, Milwaukee, WI.
“CIBO Energy Efficiency Handbook”
CIBO, Burke, VA.
“Boiler Efficiency Facts,” Cleaver Brooks, Milwaukee, WI.
“Combustion Analysis Basics,” TSI Incorporated, Shoreview, MN.

Sharon Haycock, LEED AP O7M is Commissioning Administrator at P1 Group, Inc., Lenexa KS.