Gas central heating is the most widely used type of heating system in Germany. It affordably combines advanced technology with high efficiency. Another benefit to note is that gas heating systems are ideal in combination with solar thermal systems and can also be installed easily when modernising older buildings.
In principle, this technology is quite easily explained: the heat latent in flue gas is recycled. This heat recovery has a clear benefit for consumers in that the appliances utilise gas as a fuel to the optimum degree. This can be seen in the flue gas temperatures, as older low temperature appliances are known to have generated flue gases as hot as 160–200 °C, condensing boilers expel hot vapour at only 60 °C or thereabouts. (Here we'll show you what this means for the modernisation of older systems.) Consequently, low temperature appliances are only viable in certain cases. For example, if you have several gas appliances connected to a single flue shaft in a multi-storey apartment building, if you only need to replace a single appliance or if it is not possible to renovate the entire system.
If homeowners purchase a condensing boiler and also insulate the heating system pipework, for example, they will benefit from heating cost savings as high as 30 %. Savings as high as approx. 50 % are possible in combination with solar thermal systems.
Advanced condensing boilers are ideal in combination with solar thermal systems. A collector area of as little as four square metres is enough to meet more than half the annual demand for domestic hot water in a four-person household.
If the solar thermal system is also intended to backup the heating system, the collector area must be at least twice as large, i.e. around eight square metres. This allows additional gas savings of between 10 % and 15 %. And if you complement your solar thermal system with an advanced condensing boiler, you'll qualify for state subsidies.
The fact that gas is a clean energy source keeps the cost of servicing the heating equipment low. And you can also dispense with fuel storage equipment in your house.
A new gas boiler with condensing technology may require all the radiators to be replaced, the pipework to be re-insulated or the flue system to be modernised. Although it is always possible to employ gas condensing technology in principle, the system efficiency can only be increased significantly in conjunction with these measures.
Condensing technology mostly requires the installation of a plastic flue system in existing chimney flues. This is because the low flue gas temperatures can otherwise lead to "fouling" of the chimney shaft with rot and mould.
Where you have several old, low temperature appliances connected to a single flue shaft, for example in a large apartment building, it is usually worthwhile updating all appliances to the latest condensing technology standard and modernising the flue shaft. Only where this is impossible, would it make sense – in exceptional cases – to select a low temperature appliance meeting the ErP standard, i.e. one which meets the European environmental standards. The best thing to do is contact a contractor who can check the system and the flue shaft for you.