Some Technical Aspects of Wood Pellet Boilers

Today I thought I might make a few comments on the technical side of wood pellet heating from the perspective of the buyer.

There is a very large array of wood pellet heaters and chetral heating boilers on the market. I am dealing in this blog specifically with central heating boilers. There are several different technologies used in these units. I have had some training in central heating, and I get confused with the technology, so I will attempt a brief and simple outline of WHAT IS WHAT.


Boilers versus Burner Units

First let me make a clear distinction between the parts of a Wood Pellet Central Heating Unit. The big, and heavy bit is the boiler The picture above shows a Dor Wood Burning Boiler. It is essentially a "kettle" in which water is heater, on much of the main-land European continent the word kettle is used to describe a boiler. The same type of boiler, more or less, is used for oil fired heating. The retail cost of the above boiler in Germany in 24 Kw size is approximately €850 including German VAT.




On the left is a Scotte Wood Pellet Burner unit. This is the equivalent of an oil burner unit, and essentially it could be fitted into just about any boiler. These units are the expensive part of a wood pellet c/h unit. A "Scotte" burner, like the one shown on the left, sells in Germany for about €2100 incl. of German VAT for a 16Kw size. The larger capacity burner units cost extra.

Some complete units have an integrated burner unit like the "Baxi". In the area of seperate burner units, there are 3 main types. 1. Bottom feed type, 2. Top fed type, and 3. Lateral feed. All use an igniting element and a feed system to control the flow of pellets. Essentially there is a burning pan or chamber into which the pellets are fed, then ignited. Once lit a fan is used to blow the flame.


Some of the other pieces needed to complete a Wood Pellet Unit include a motorised Auger which transports the pellets into the burner, and a Lambda Unit, which controls the oxygen in the burn process. Also needed is some sort of storage bin or hopper which holds between 5 and 14 days of pellets, depending on capacity.