What is a combi boiler

Combi boiler: Biomass boiler as an environmentally friendly alternative

Heating with biomass is trendy for several reasons. The fuels are cheap, come from renewable sources and have a good price forecast. Read more about the advantages that a flexible combi boiler that can be operated with logs as well as wood chips or pellets offers you on Efficiency House-online!

This is how the pellet heating works with the combi boiler

A combination boiler is a biomass heating system that can be operated with logs and pellets or wood chips at the same time. The combination of pellets and split logs is much more important. The combined fuel boiler combines the advantages of a pellet heating system and those of a log boiler. The devices are designed as log gasification boilers with a flange-mounted pellet burner. If necessary, the log boiler is usually requested first. If it is empty, the pellet burner starts up.

You only have to fill the device once a day and the required heat is automatically provided. Or you use inexpensive firewood from private sources in everyday life, but enjoy the advantages of automatic pellet heating when you are absent for a longer period of time. The main advantage is that you can heat in an environmentally friendly and flexible manner and at the same time take advantage of price advantages. On the other hand, combi boilers are usually somewhat lower in efficiency than pure specialists.


From a simple omnivore to a highly efficient heating system

As with most heating systems, the range of devices offered is also large in the area of ​​combi boilers. It is very important to differentiate and understand your needs before buying. In the entry-level segment, there are simple and inexpensive "omnivores", where the operator pays for his flexibility with significant losses in efficiency. Often the cheapest devices with the log gasifier do not achieve the emission values ​​required for funding by the BAfA. Also due to the higher consumption costs, this is usually not recommended in the long term, despite the savings in the purchase price. Highly developed devices are technically much better positioned.

Combined boilers from leading suppliers are often equipped with two separate heat exchangers, a stepless suction fan and an automatic cleaning function. This enables them to achieve considerable efficiencies of well over 90 percent. Some systems even allow partial load operation with very good emission values ​​and high efficiency. Similar to the pure log gasifier, the performance classes start at 20 kW. Energy efficiency drops below this size. That can be a lot for a smaller family home. A sufficiently dimensioned buffer storage tank ensures that the heat produced can be used efficiently.


Combi boiler: cost of acquisition

If you want to buy a combination boiler, you should plan an amount of EUR 5,500 or more for the boiler itself. In addition, there are usually costs for a large buffer tank and other components of the heating system. Assembly also makes up a not insignificant part of the total costs. The average is 8,000 to 11,000 euros.


Operating costs of combi boilers

As expected, the consumption costs are somewhere between those of a pellet heating system and those of a log boiler. As an example, a typical value for a single-family house with a heating requirement of 25,000 kW is given: In terms of heating and hot water costs including maintenance, chimney sweeps, etc. are to be expected here with about 2100 EUR annually.


High BAFA funding for combi boilers from 2017

The BAfA funding for combi boilers is as attractive as that for pellet, woodchip or log boilers. The prerequisite for this is a sufficiently large buffer store with at least 55 liters per kW and at least partially automatic charging. The basic funding is EUR 3,500. In addition, you can apply for additional bonus grants and innovation grants. Talk to your heating engineer about this!


Source: Bosch Thermotechnik GmbH
Photo: ATMOS Zentrallager GmbH