From a traditional boiler to a condensing one: technical considerations and critical issues


Emma Potter

The condensing boilers they represent a choice more sustainable and economical compared to traditional boilers, both because they are able to implement more efficient combustion and because they are able to exploit the higher calorific value of the fuel; however, in interventions on existing systemsthe replacement of a traditional generator with a condensing one turns out not without its critical issues.

The transition from a traditional boiler to a condensing boiler in fact involves the adoption of one series of measures aimed at adapting the existing system to the technology used by the new generator. It is essential to check the compatibility between the existing heating system and the new generator, as some systems may require even major modifications in order to fully exploit the advantages of condensing boilers.

Condensation management

One of the most relevant aspects is the condensate management. Condensing boilers produce condensate as a by-product of combustion. This requires the creation of a drainage system, through connection to the sewage system or installation of a dedicated drainage system, which must be made of corrosion-resistant materials; the condensate is in fact acidic due to the presence of carbonic acid.

The exhaust system it must turn out adequately designed and sized to allow the safe and efficient disposal of condensate; to this end, the location of the boiler must also be carefully evaluated. For small wall-mounted boilers the condensate can be sent directly into the drainage network, without a chemical treatment that reduces its acidity; for larger generators, however, devices are required to reduce harmful substances as required by the UNI 7129 series standards.

Modifications to the flue and fuel compatibility

There condensate production also requires modifications to the fluewith particular reference to the following aspects.

Dimensions and materials of the flue. Condensing boilers require a flue of adequate size to allow the effective disposal of exhaust gases; furthermore, the flue must be made of corrosion-resistant materials, such as stainless steel, to manage the presence of condensation.

Slope changes. As condensing boilers produce condensate, it is important to ensure an adequate slope of the flue to allow the condensate to drain properly. This may require adjusting the slope of the chimney or installing additional components, such as a drainage system.

Separation of exhaust systems. If you intend to use the condensing boiler together with other boilers or smoke generators, it is necessary to separate the exhaust systems to avoid condensation problems or contamination of the exhaust gases.

Thermal insulation. It is also necessary to provide thermal insulation of the chimney, to minimize heat dispersion and improve the efficiency of the system.

In addition to the technical aspects related to condensate management, when switching from a traditional boiler to a condensing boiler it is necessary to take into consideration the fuel compatibility: condensing boilers work better with some types of fuel, such as natural gas or LPG; however, if other fuels are used, adaptations or the installation of additional components may be necessary to ensure efficient operation.