Vitoflex 300-UF – wood boiler with grate combustion

Take advantage of these benefits

  • Fully automatic wood boiler with grate combustion
  • Rated heating output range: 390 to 1250 kW
  • For the use of wood fuel with a moisture content of up to 50 % (M50, to EN ISO 17225-1)
  • High efficiency thanks to proven combustion technology, three-pass heat exchanger, modulating output control and regulated primary and secondary air supply
  • Permissible flow temperature up to 100 °C
  • Maximum operating pressure: 6 bar
  • Easy maintenance thanks to fully automatic ash removal and optional pneumatic cleaning system
  • Highly developed safety equipment ensures safe and reliable operation
  • Optimum system output results from the design and delivery of all system components from a single source
  • Automatic ignition avoids the need to maintain the firebed and saves fuel (optional – only for fuels with moisture content below 40 %)
  • Individual design of your system by our team of experts
  • Excellent output control from 30 to 100 %

Top quality design and construction

The Vitoflex 300-UF wood boiler features high quality construction for use under the toughest conditions (high fuel flexibility from M10 to M50).

The inside of the combustion chamber is lined with pressed fireclay bricks with a high clay content for greater durability. All grate elements are high quality, heavy gauge chromium steel castings that can withstand very high temperatures.

A distinguishing feature of the Vitoflex 300-UF wood boiler is its proven three-pass heat exchanger, providing maximum heat transfer and exceptional efficiency.

Wood boiler with state of the art grate combustion, from 390 to 1250 kW. For wood fuels with a maximum moisture content of 50 percent.

The moving infeed grate, proven combustion retort and sloping external grate in the Vitoflex 300‑UF optimally combine the benefits of infeed and underfeed combustion. A feed screw conveyor guides the wood fuel into the combustion retort, where it is pre-dried. The fuel is completely degassed on the external grate and the moving infeed grate. The wood gases are then burned with the aid of a regulated supply of secondary air.

Clean and efficient combustion

The combustion technology of the Vitoflex 300-UF achieves low emission values (particularly for CO and NOx). Operation with modulating output control and the optimised combustion principle enables efficiency levels of up to 92 percent.

Product cross-section


Output (kW)
390 to 1250 kW
Rotation combustion
Permissible flow temperatures
up to 100 °C
Maximum operating pressure
6 bar
up to 92 %
Pellets, woodchips (max. M50/G50), wood remnants
Application range
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Large residential buildings, commerce, municipal offices, new build and modernisation projects
Additional features
Fully automatic ash removal. Modulating output control from 30-100 %. Automatic ignition precludes the need for firebed maintenance and saves fuel.
Produktschnitt Holzkessel Vitoflex 300-UF