The conveyor system transports the pellets from the store room to the heating boiler. Three different systems have established themselves in this regard:

Vacuum-extraction system

The use of an extraction system is recommended for long distances. The pellets are transported in the hose. The system overcomes distances of approx. 25 m and ascents of approx. five meters without difficulty. A suction blower transports the pellets in a closed air circuit. A suction turbine is required for this, which can also be integrated in the boiler.
However, suction conveyor systems are relatively noisy compared to screw conveyors. The cycle time must therefore be set in a manner to ensure that running operation does not inconvenience the house owner. The control is done by the boiler.

Screw conveyors

The use of a screw conveyor is suitable for short distances, i.e. up to three or four metres. The rotating screw moves the fuel continuously to the boiler at low noise. The boiler controls the screw and requests the pellets automatically, as needed.

Spiral conveyors

As screw conveyors, spiral conveyors ensure low-noise, dust-free transport of wood pellets. It works also in bends and ascents; energy expenditure is low. However, spirals are more flexible than screws, and the soft movement of the spiral protects the wood pellets against damage.

A combination of a suction conveyor and a spiral conveyor is also possible. In this case, the spiral is used to transport a defined amount of pellets to an extraction point.
The cascade design also shows the flexibility of a spiral. Here, several silos are connected by one continuous spiral.