What is condensing technology?

Extra efficiency

In the normal combustion, the accruing water escapes unused in the form of flue gas through the chimney. Conversely, with condensing technology, the residual heat contained in the flue gases from pellet combustion is also utilised. The water vapour is cooled down below the condensation temperature for this purpose. The process produces liquid condensate that releases heat during the transformation. This additional heat gain is fed in turn into the heating system, where it can be reused.

Heating systems with condensing technology utilise almost all the energy contained in the exhaust gases from pellets. This additional benefit of approx. 16.3% with pellets is simultaneously the energy saving made possible by condensing technology. This saves money. This allows condensing boilers like the Pellematic Condens to achieve efficiency levels of up to 107.3%.

Condensing technology subjects the flue gas quite naturally to additional cleaning – emission levels are therefore significantly lower than the legal limits. Pellet boilers with condensing technology achieve a reduction in dust emissions of 40–50% compared to standard boilers without condensing technology. Modern pellet boilers are therefore not comparable in any way with old wood boilers either as regards emissions. So a condensing boiler helps not only to reduce energy costs, but also to protect the climate.

Due to their high efficiency with lowest emission levels, pellet condensing boilers also qualify for particularly attractive subsidies from the state.

Prerequisites for installing a condensing boiler:

  • A corrosion-resistant chimney
  • Return temperatures of approx. 30–40 degrees
  • A drain for the discharged condensate



Other terms

The net calorific value is defined as the thermal energy released during combustion and subsequent cooling to the initial temperature of the combustible mixture, whereby the combustion water is vaporous. The net calorific value of fuels rich in hydrogen is therefore significantly lower than their gross calorific value.

The gross caloric value describes the thermal energy of a fuel which is released during combustion and subsequent cooling of the combustion gases to 25 degrees Celsius and their condensation. The big difference compared to the net calorific value is the inclusion of the energy released by condensing any water vapour produced.

Gross calorific value = net calorific value + latent heat of condensation

The efficiency describes how much of the input energy is actually used. Our ÖkoFEN pellet boilers operate very effectively, make optimum use of the energy content and can heat very efficiently with pellets.
The efficiency of our modern pellet boilers even exceeds 100%, because, to enable comparability with all other pellet boilers on the market, the calculation is based on the net calorific value – this is the current state of the art as per EN 303-5. (If the gross calorific value of the fuel is used as the reference value, efficiencies over 100% are, of course, physically impossible.)

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