A condensing boiler is a modern, energy-efficient heating device that can almost completely utilize the energy released during the combustion of fuel. Unlike traditional boilers, it not only uses the calorific value of the fuel, but also the latent heat from the condensation of water vapor in the flue gas, thereby significantly increasing its efficiency.
The operating principle of a condensing boiler
Fuel combustion: Condensing boilers usually operate with natural gas, which consists of hydrocarbons. During combustion, the hydrogen in the hydrocarbons is converted into water (water vapor) and the carbon is converted into carbon dioxide.
Flue gas utilization: In traditional boilers, due to the high temperature of the flue gas (120–200 °C), significant energy is lost through the chimney. In a condensing boiler, the flue gas temperature is much lower (approximately 50–60 °C), as the water vapor in the flue gas condenses and the latent heat energy released is also utilized.
Condensation process: The temperature of the return heating water is low (typically 40–50 °C), which allows the water vapor in the flue gas to condense. The energy released during condensation is used to further heat the heating water.
Increased efficiency: The efficiency of a condensing boiler can be up to 98–109% (based on lower heating value), as it utilizes not only the energy of the fuel, but also the condensation heat.
Advantages of a condensing boiler
High efficiency: It can operate with up to 20–30% higher efficiency compared to traditional boilers, especially in low-temperature heating systems (e.g. underfloor heating).
Energy saving: Less fuel is needed to produce the same amount of heat energy, resulting in lower heating costs.
Environmentally friendly operation: Condensing boilers emit less carbon dioxide (CO₂) and other harmful substances, reducing the environmental impact.
Compatibility with low temperature systems: Ideal for underfloor heating or other heating systems with low flow temperatures, as these systems maximise the condensation effect.
Compact design: Modern condensing boilers are smaller, easy to install and require less maintenance.
Important considerations when using condensing boilers
Return water temperature: Condensation only occurs when the return water temperature is low enough (below 40-50°C). Therefore, these boilers operate most efficiently in low temperature systems.
Condensate drainage: The condensation process produces acidic condensate which must be drained into a suitable drainage system. A neutralisation device may occasionally be required to reduce the pH value.
Appropriate chimney system: Due to the low temperature of the flue gas, a special chimney system designed for condensing boilers must be used, which is resistant to acidic condensate.
Installation requirements: Before installing a boiler, it is worth consulting with an expert to ensure that the system is compatible with your home's heating needs and infrastructure.
Summary
Condensing boilers represent the pinnacle of modern heating technology, with their efficient energy use and environmentally friendly operation. Unlike traditional boilers, they not only utilize the calorific value of the fuel, but also the condensation heat, thus ensuring lower energy consumption and lower emissions. They are an ideal choice for low-temperature systems, such as underfloor heating, and are an essential element of sustainable heating systems.