Which gas boiler should you choose: with an atmospheric or a forced-draught burner?

By the way combustion air is supplied, gas boilers are divided into atmospheric boilers and boilers with forced-draught burners. In atmospheric boilers, fuel is mixed with combustion air through natural circulation, and in forced-draught boilers by forced ventilation. Let's compare the two types of boilers on several parameters.

Safety

Atmospheric boilers have an open combustion chamber. This means their owners will need a wide chimney with good draught and supply ventilation. Forced-draught burners are safer, as fuel burns in an enclosed space. Boilers with forced-draught burners do not require a tall chimney (thanks to the forced-draught fan).

Efficiency

Atmospheric boilers have a simple design without a fan or motor, so they work almost silently. Due to their basic operating principle - natural air circulation - heat leaves such boilers quite quickly. An important point: boilers with atmospheric burners are very sensitive to gas pressure fluctuations, which can cause the burner to burn through.
Combustion in boilers with forced-draught burners is more intense, so their efficiency is significantly higher. Forced-draught burners have a complex design that always includes a fan and an electric motor. The forced-draught burner forces air into the chamber. This flow is regulated automatically, which ensures stable combustion even when gas pressure fluctuates. Forced-draught burners provide higher boiler output, also thanks to the special heat exchanger design - a double-walled "barrel". The burner flame works inside it, and the heat carrier circulates between the walls. As a result, heat is taken from the burning gas not only above the burner, as in atmospheric boilers, but also beside the flame, allowing a larger volume of liquid to be heated per unit of time.

Fuel types

Atmospheric boilers run only on gas, while boilers with forced-draught burners can be dual-fuel (gas/diesel/fuel oil), so their owners can use both gas and liquid fuel. In addition, fuel burns almost completely in them, unlike in atmospheric burners.

Cost

Which burners do you think are more expensive? Most often forced-draught ones. This is due to their complex design and high performance. In addition, the electric motor in forced-draught burners has a certain service life (about 10 years) and consumes additional electricity. But don't jump to conclusions! Atmospheric boilers require a tall and wide chimney (usually quite expensive), and overall the cost of a heating system with atmospheric boilers may be no less, or even more, than with gas boilers with forced-draught burners, which are far more reliable, efficient and safe.
And owners of forced-draught burners can save about 20% of fuel by installing an economiser on the boiler flue outlet.

Service life

The electric motor of a forced-draught burner lasts about 10 years. How long an atmospheric burner will last with unstable gas pressure is a big question.
Thus, boilers with forced-draught burners have higher efficiency, are safe and work stably, but cost more in electricity and are noisy. Atmospheric boilers are cheaper and quiet, but less efficient, sensitive to gas pressure fluctuations and require good ventilation and a chimney. All FACI gas boilers (two-pass and three-pass) are equipped with forced-draught burners.

We have covered the important points and hope
our article will help you make the right decision!