Vitoflex 300-UF

High-tech and reliable

State-of-the-art underfeed combustion wood-fired boiler, for wood fuels with maximum water content of 50%. Max output: 1331 to 4265 MBH.

Fully automatic boiler
CO₂ neutral heating
Ideal for commercial applications
Output up to 4265 MBH

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Highly efficient

With advanced combustion technology, triple-pass heat exchanger and modulating output control (turndown ratio 4:1).

Low maintenance

With fully automatic de-ashing, optional pneumatic cleaning system and flue gas de-duster.


Advanced combustion process keeps emissions of CO and NOx to levels comparable to those of modern fossil fuel boilers.

Built to last

All components are made of high-quality materials to ensure lasting performance.

Maximum heat transfer

With triple-pass heat exchanger design.

Advanced safety equipment

Ensures safe and reliable operation.

Grate firing at its best

The Vitoflex 300-UF boiler uses a burner trough with an attached external grate and a moving annealing grate to achieve optimal combustion results. A feed auger moves the wood fuel into the burner trough where the fuel is pre-dried and gasified under precisely controlled primary air (underfeed combustion). On the external and the moving annealing grate the fuel completely gasifies (syngas). Precisely controlled secondary air is injected to fully combust the syngas and thermal energy is released into the boiler's triple-pass heat exchanger.

Quality design and construction

The Vitoflex 300-UF boiler is quality-constructed to handle the toughest of loads. The combustion chamber is lined with compressed firebricks with a high alumina content for added durability. All grate elements are made of durable cast chrome steel to withstand even the highest temperatures. The Vitoflex 300-UF boiler features a classic triple-pass heat exchanger design for maximum heat transfer and efficiency.

Clean-burning and efficient

Equivalent in quality to modern gas combustion, the advanced combustion process of the Vitoflex 300-UF keeps emissions of CO and NOx to levels comparable to those of modern fossil fuel heating systems.

Plus, unlike oil and gas, wood is a CO₂-neutral, renewable form of energy. Used with our digital, modulating-output control, the Vitoflex 300-UF boiler achieves an efficiency of 85%.

Advantages of the Vitoflex 300-UF

Fully-automatic underfeed combustion wood-fired boiler.
High efficiency and ultra-low emissions with precisely controlled primary and secondary air.
Maximum system performance with heavy-duty construction and all system components from one source.
Automatic ignition device limits idling and saves fuel (optional – only for fuels with less than 40% moisture content).
Five models from 1330 to 4268 MBH (390 to 1250 kW).
Available for 30 or 60 psig max. operating pressure.

Look inside the boiler

  1. Infeed auger with light barrier
  2. Burner trough with internal grate
  3. Moving grate
  4. De-ashing system
  5. High-temperature burnout zone
  6. Triple-pass heat exchanger
  7. Safety heat exchanger
  8. Pneumatic cleaning system

Product details

Max. output

1331 MBH (390 kW) for UF-390
1808 MBH (530 kW) for UF-530
2457 MBH (720 kW) for UF-720
3242 MBH (950 kW) for UF-950
4265 MBH (1250 kW) for UF-1250

Min. output

334 MBH (98 kW) for UF-390
450 MBH (132 kW) for UF-530
614 MBH (180 kW) for UF-720
812 MBH (238 kW) for UF-950
1065 MBH (312 kW) for UF-1250



Max. fuel moisture content


Max. operating pressure

30 or 60 psi (2 or 4 bar)

Max. water temperature

250°F (120°C)

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