How to choose a gas boiler?

 The knowledge of the heat loss of your building will tell you what gas boiler to buy into your house. If it is a new building, this information is part of the project documentation regarding the renovation and have the heat loss calculated by an expert. You can calculate the approximate performance HERE. Please note that this is only an approximate value for your estimation of which boiler you should be interested in. For sure, it is recommended to find out the value by an expert.

When selecting a boiler, it is also necessary to take into account the connection of the boiler with the flue gas path. There are two options:

Gas boilers with chimney flue

This is a traditional form of flue gas exhaust where the flue gas is routed to a chimney, but it is necessary to regularly revise it. In the room where the boiler is located, sufficient air supply must be ensured.

Gas boilers with forced flue gas exhaust

This option is used in cases where it is not possible to have a classic chimney exhaust. Boilers with this variant of flue gas can be found under the designation gas turbo boilers. The main difference is that the flue gas is discharged via a fan and a special exhaust system out through the wall of the room on which the boiler is mounted. Another option is to discharge the air perpendicularly through the roof. Air is sucked into the boiler from outside, so it is not necessary to solve the air supply to the room. This is typical for condensing boilers.


Types of gas boilers

In a gas boiler it is also important to distinguish whether you need it only for heating or as a source for water heating. In this respect, gas boilers are further divided into:

  • Gas fired boilers - used only for heating.
  • Gas boilers with heating - suitable for heating and hot water. So called combined gas boiler.
  • Condensing boilers


Condensing boilers

Condensing boilers have a really high efficiency, even over 100%. Normal gas boilers have an output of around 90%. It is suitable for underfloor heating, but also for higher heating water temperatures. The advantage of condensing boilers is that they consume up to 30% less gas and emissions are up to 70% lower. Thanks to the technology, condensing boilers are more expensive than conventional gas boilers, but in recent years the differences between prices have decreased significantly.

How does a condensing boiler work?

With condensation boilers, hydrogen-containing methane (CH4) or propane (C3H8) is produced during the combustion of natural gas, which is heated and converted into water vapor. This water vapor together with carbon dioxide, together called flue gas, then generates additional thermal energy. And this is the main principle of condensing boilers. Not only is there a flame inside the boiler, which heats the heat exchanger with heating water, it is also created flue gas, which heats the second exchanger, into which flows the cooled water, which has already passed through the entire heating system.
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For a better idea of ​​the functionality of the condensing boiler, see the video published by Vailant Group Czech Republic, entitled "How Vaillant Condensing Boilers Work".