Increasing Steam Boiler Efficiency with a Vent (Flue) Damper

metal flue vent with floral design in brick wall

Fitting a flue damper is an excellent way to improve the efficiency of your boiler. All boilers which burn fuel need to be vented which will allow the fumes to escape without building up and causing danger to people inside the house. The problem is that heat will be lost through the chimney if it is left open all the time.

A vent flue damper is an automatic device which will open whenever your boiler fires up to allow the fumes to escape, but close again to prevent too much heat escaping.

Steam Boilers

Although a vent damper is a beneficial addition to any type of boiler it's even more useful when working with steam boilers. A steam boiler is a special type of boiler which was very popular during the early 20th century. This type of boiler does not need any pumps to circulate the hot water because it relies on the pressure of steam.

The boilers will boil the water until it becomes steam which is then pushed around the pipes to the radiators. There are a few unique factors when using these types of boiler. When hot water is required the boiler will fire up producing steam which is then pushed through the pipes. However, there will already be air in these pipes.

The air must be allowed to escape through a vent in the radiator but for efficiency this vent must close off again automatically as soon as the hot steam has filled the radiator. Although steam boilers aren't commonly fitted any more there are still a lot of them in existence. They are very reliable and are often still working in older homes which is why many homeowners are interested in fitting flue vent dampers.

Mechanical Vent Dampers

A mechanical flue vent damper will greatly improve the efficiency of your steam boiler. This is an automatic device which will shut the flue off once the burner stops firing. This means that heat will stop being lost through the chimney. Installing a vent flue damper will normally cost somewhere between $100 and $400 depending on the complexity of the project and the model of your boiler.

Gravity actuated vent dampers aren't as useful because they can cause extra back drafts, which will waste some of the heat in your home. As steam boilers get hotter it will be even more efficient and useful when using vent dampers.

Fitting a vent damper is actually very simple. First the boiler will need to be shut off and the flue given plenty of time to cool down before working on it. Then a section will be cut out of the flue which is where the damper will be fitted. This is a mechanical in-line damper which will automatically rotate to shut off the flow of hot gas from the boiler.