Home News Replacement of a boiler with a condensing boiler

Replacement of a boiler with a condensing boiler

News | 23. 10. 2020

The condensing boiler is the most efficient device for heating and water heating. When compared to an older gas boiler, this can means a reduction of operating costs by up to a third. More and more households with a gas connection install it especially thanks to its low operating costs.

However, condensing boilers also have their issues. How to avoid them, and what to pay attention to when installing them?

Family houses

In family houses, the condensing boilers replace either old gas boilers or solid fuel boilers. In both cases, it is necessary to consider the necessity to install a condensate drain. During operation a large quantity of condensate is created and in practice it is therefore necessary to connect the boiler to the waste drain. This can be a problem, for example, in cellars or boiler rooms where no water pipeline is installed. In such cases it can be solved with a condensate pumping station, which is available in accessories of condensing boilers. It is made of a reservoir and a small pump, which pumps the condensate to the sewerage located above the level of the boiler output.

The necessity of chimney lining is often the second unexpected investment. The condensing boiler flue gases have a low temperature and act as a weak acid and that is why polypropylene-based pipes are used. Their advantage consists in their simple installation and low price.

Condensing boiler in an apartment

One of the basic requirements of apartments for their heating source is the size of the heating source, because in case an apartment does not have its utility room, the boiler is installed in the bathroom, hall or even the kitchen. There are various condensing boilers on the market, the dimensions of which are not bigger than the dimensions of a classic gas flow-heater. They can also be hung on the wall and heat the warm water with flow-heating.

For example, the THERM 25 KDZ 5 hung condensing boiler can also be hung on the wall with an integrated hot water reservoir of a volume of 55 liters, which is covered by the boiler case.


Thermona Sales Director


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A new boiler is a reason to revise the whole system

The reconstruction of heating system is usually made after ten or more years. It is therefore necessary to consider how much the parameters of the house and its heat demand have changed since the installation of the original boiler.

The condensing boiler achieves its highest efficiency at a lower temperature of heating water. It is therefore appropriate to made a complete review of the heating system, including radiators, which are usually dimensioned for a higher temperature of heating water. We often encounter concerns that it will be necessary to replace the radiators with the replacement of a boiler with a condensing boiler. It is true that for older houses their area was dimensioned for a higher heating water temperature, but at the same time, if the windows were replaced or the house was insulated, the energy demand of the building has been significantly reduced.


Thermona Sales Director

Attention to the installation site

As the modern boilers are also great at their quiet operation, the specific location of the boiler in the apartment is usually determined with the possibility to connect the flue gas outlet and the air supply. When the boiler is placed directly in the apartment interior, it is possible to use a chimney shaft and to use double polypropylene pipes, so-called coaxial pipes, to take out the flue gas and to supply the combustion air. The flue gas output of the condensing boiler can be installed both through the roof and the perimeter wall, depending on the more advantageous solution in the specific place of installation. Here, it is also necessary to consider the condensate drain.


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