Flue gas temperature and chimney losses: how they affect efficiency

Flue gas temperature is a key factor in estimating the thermal losses of a boiler or burner.

High flue gas temperature

It may indicate increased losses to the chimney, a dirty heat exchanger, or an excessively high load.

Very low temperature

In non-condensing systems, it can cause unwanted condensation and corrosion.

Relationship with combustion air

Excessive combustion air increases the mass of the flue gas that is heated and expelled.

Evaluation

The temperature is examined in conjunction with O₂, CO₂, CO, combustion air temperature, and the boiler specifications.