How to Remove Carbon & Soot From a Boiler Heat Exchanger


A heat exchanger on a boiler functions the same way that it would in a furnace, by transferring heat produced by the fire into a heat transfer medium. In a boiler this transfer medium is water. Soot and carbon monoxide residues can build up on the heat exchanger, and rust from condensation inside the unit can also form. Cleaning your boiler’s heat exchanger takes only minutes and can improve the efficiency of your boiler. Soot and combustion gas residue restrict air flow within your exchanger, which pushes more heat up your chimney and can cause the heat exchanger to overheat.

Things You'll Need

  • Screwdriver
  • Face mask
  • Safety goggles
  • Stiff bristled nylon brush
  • Vacuum
  • Cloth
  • Turn off the main power supply to your boiler by switching off the breaker at the panel or removing the fuses connected to the unit.

  • Shut off the gas supply to your boiler by closing the main gas supply valve. Allow the furnace to cool completely before you begin cleaning the heat exchanger.

  • Wear a face mask to prevent inhalation of dust or fumes and safety goggles to protect your eyes.

  • Remove the outer case or the base panel of your boiler using a screwdriver. If there is a cleaning access cover over the heat exchanger, remove this as well.

  • Rub a stiff nylon bristled brush over the heat exchanger tubes to loosen debris and carbon monoxide residue. Brush all parts of the heat exchanger and the housing to loosen all material.

  • Vacuum away dust and soot build up loosened by the brush. Use a brush attachment on your vacuum nozzle.

  • Wipe the heat exchanger tubes with a damp cloth to remove any remaining residues. Avoid using household chemicals such as bleach, aerosol sprays or muriatic and hydrochloric acid to clean your boiler. These can cause the heat exchanger to corrode rapidly.

  • Reattach the access panel or casing and refasten screws to secure. Turn the power and gas supplies back on.

Tips & Warnings

  • Heat exchangers should be cleaned at least twice each year, but increased usage may require cleaning more frequently. If your boiler is not producing sufficient heat or doesn’t ignite properly, these problems indicate the heat exchanger may be clogged. Keeping the heat exchanger free of soot and residue ensures efficient operation because material building up on and around the tubes will act as an insulator and obstruct the transfer of heat.

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