How to Troubleshoot Gas Boiler Dampers


Gas-fueled boilers operate as part of a home’s heating and cooling system. The boiler replaces the furnace device commonly found in forced-air heating and cooling systems. As gas boilers rely on the combustion of fossil fuel materials, dampers help regulate the release of byproduct gases and fumes. Troubleshooting a gas boiler damper involves inspecting the devices that work in tandem with the damper mechanism.

Gas Boiler Dampers

  • Within a home’s heating and cooling system, the gas boiler damper sits in between the gas burner and the chimney flue. The chimney flue, in and of itself, directs byproduct combustion gases into the outside air. It does this using air currents or drafts that move between the gas burner compartment and the chimney flue. Differences in air pressure allow for a natural upward flow of air currents through the chimney flue. These air currents respond to a suction effect caused by the weak air pressure in the flue versus the stronger air pressure in the room where the burner sits. The damper device includes a weight system that responds to changes in air pressure. In effect, the damper opens and closes to allow or prevent airflow when changes in air pressure occur.

Combustion Processes

  • Combustion processes involve creating the proper mixture of gas and air so fuels burn safely and efficiently. Within a gas boiler system, the damper (more commonly known as draft regulator in gas-powered system) regulates the air and gas levels within the combustion chamber or compartment. Faulty damper operations can offset air-gas mixtures and potentially produce dangerous carbon monoxide gases as a byproduct. Improper combustion processes can also reduce a system’s energy efficiency levels. Troubleshooting combustion processes may require having a licensed technician measure for carbon monoxide gas emissions.

Rust & Debris

  • As gas boiler dampers rely on differences in air pressure between the room air and the flue passage, any blockages in the chimney can cause gas and burner elements to function improperly. Rust or debris along burner surfaces or along the surface of the combustion chamber may indicate inadequate flue draft. Inadequate flue draft can result from a blocked chimney chute or from a chimney stack that’s too short to generate a draft. In general, chimney stacks should stand at least 3 feet higher than the roof surface and a minimum of 2 feet higher than any nearby roof structures.

Mechanical Problems

  • Mechanical problems affecting the door that opens and closes the damper can disrupt airflow within a gas boiler system. Since the damper door operates on a weight-adjusted balance, a maladjusted door or a missing weight will not allow for the proper opening and closing of the damper.

    Mechanical problems with dampers may also involve the location of the system’s draft hood cover in relation to the gas burners. The draft cover acts as a canopy for the combustion chamber and must sit within a certain distance of the gas burner in order to generate the needed gas and air mixtures within the chamber. Manufacturer specifications determine how far away a draft hood should sit from the burner. When positioned too close or too far away, the damper device may not work properly. These conditions create a potentially dangerous combustion environment.

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