Yet there is still enough heat in the hot flue gases – to be more precise, in the hot water vapour – to be used for heating. You can feel this heat in a simple way: if you hold your hand over a pot of boiling water, sooner or later you will have to withdraw it. This is because the hot steam rises from the boiling water and condenses on the palm of your hand. As it condenses, the steam then releases its latent heat, also called the heat of condensation.
In order to increase the energy efficiency of an oil heating system and to develop combustion technology that is more resource-efficient in the long term, it is important to recover this heat in a controlled manner and feed it back to the heating system without the condensate damaging the system or the flue. The operating principle of oil condensing technology therefore also includes deliberate condensation of the hot flue gases.