Pellet heating boiler as central heating
At present there are two different types of pellet boiler available; semi-automatic and fully-automatic. These two pellet boiler types are differentiated by the work required to fill the pellet bin or the storage room; the semi-automatic compact systems have a large pellet bin which is filled manually. Recommended here is a reservoir volume of at least 400 l; this is the equivalent of approx. 260 kg of pellets. Fully-automatic pellet boilers on the other hand are connected directly to a pellet store via a vacuum system or auger with which the pellets are automatically conveyed to the stove.
Pellet boiler with auger: The pellets are conveyed with an auger from the store to the pellet boiler. This system is simple and cost-effective and is therefore frequently used. The boiler must however be in the immediate vicinity of the pellet store.
Pellet boiler with vacuum system: The pellets are sucked or blown via a pipe from the pellet store into the boiler. This represents a very flexible solution. The hose can be up to 20m long depending on manufacturer and convey the pellets up to 6m high.
The latest developments in pellet boiler technology are condensing appliances with stainless steel heat exchangers and wall-mounted pellet appliances which work on the basis of low temperature technology. The clever solution of condensing appliances utilizes the energy from the flue gases. The steam in the flue gases is cooled to the point at which it condenses, releasing the energy it holds. This is reflected in a gain in heat of an additional 10% to 15%. The infinitely variable heat output of the wall-mounted pellet appliances is 2 to 7 kW. The boiler temperature can be reduced to below 38°. As a result of the small space required combined with variable external or internal tank solutions, a maximum on flexibility and space utilization is achieved.
Modern pellet boilers reach an efficiency of more than 90 % and exhibit very low emission values. Guide value for optimum combustion technology is the attainment of CO values of below 15 mg/MJ. The heat exchanger surfaces must be cleaned from time to time depending on manufacturer. This is done externally by moving a lever, or in the case of modern boilers, is fully automatic.