Underfeed firing system 390 to 1250 kW

By combining the moving forward feed grate with the proven firing depression and falling outer grate, the Pyrtec optimally unites the advan­tages of the moving grate firing system with the underfeed firing system. An infeed screw trans­ports the wood fuel to the firing depression of the wood heating section, where it is pre-dried. On the outer grate and the moving forward feed grate, the fuel is completely degasified. The wood gases are then combusted with the regulated injection of secondary air.

Underfeed firing system Pyrtec

Maximum quality of design and manufacture

Wood pellets
Wood chips
Wood shavings and mixed wood

Combining the moving forward feed grate with the proven firing depression and falling outer grate optimally unites the advan­tages of a moving grate firing system with the underfeed firing system.

Clean and efficient combustion

The combustion technology of the Pyrtec achieves low emissions values (especially for CO and NOx). Operation with modulating output regulation and an optimised combustion principle enables an efficiency of up to 92%.

Design and function

The Pyrtec wood-fired boiler is a quality product for the harshest condi­tions (high fuel flexi­bility from M10 to M50). The firebox is lined with pressed and baked ceramic bricks that have a high aluminium oxide content for higher resis­tance. All grate elements are made of high-quality, thick castings of chromium steel and are able to withstand high tempe­ra­tures. The Pyrtec wood heating boiler features a three-pass heat exchanger for maximum thermal trans­mission and efficiency.

Boiler control

The boiler is controlled by the completely programmable modulating output and system controller. This controls all variable-speed blowers as well as the fuel feeding mechanism. It also monitors the following:

  • Supply and return tempe­rature of the wood-fired boiler
  • Light barriers of the infeed system
  • Pressure sensor for reliable under­pressure
  • Flue gas tempe­rature
  • Firebox sensor (upper tempe­rature limit)
  • Oxygen content of the flue gas (lambda probe)

Design and output ratings

Type Output range*
Pyrtec 390 130 to 390 kW
Pyrtec 530 177 to 530 kW
Pyrtec 720 240 to 720 kW
Pyrtec 950 317 to 950 kW
Pyrtec 1250 417 to 1250 kW

*Depending on fuel and water content


Model Pyrtec 390 Pyrtec 530 Pyrtec 720 Pyrtec 950 Pyrtec 1250
Rated thermal output 390 530 720 950 1250 kW
Length 3282 3782 3877 3835 4380 mm
Width 1274 1274 1380 1612 1612 mm
Height 2378 2536 2834 3035 3230 mm
Weight 5230 7554 8869 11463 12918 kg
Maximum operating pressure 6 6 6 6 6 bar
Sectional drawing UF
  1. Infeed screw with barrier layer
  2. Firing depression with inner grate and primary air 1
  3. Outer grate with primary air 2
  4. Moving forward feed grate
  5. Secondary air
  6. Ignition blower
  7. Ash discharge
  8. High-tempe­rature zone for complete combustion
  9. Firebox door
  10. Three-pass boiler
  11. Safety heat exchanger
  12. Pneumatic boiler tube dedusting

Profit from these benefits:

  • Fully automatic wood-fired boiler with grate firing
  • Nominal heat output range: 390 to 1250 kW
  • For the use of wood fuels with a water content of up to 50% (M50)
  • High efficiency thanks to proven combustion technology, three-pass heat exchanger, modulating output regulation and regulated primary and secondary air supply
  • Maximum operating pressure: 6 bar
  • Simple maintenance thanks to fully automatic ash removal and optional pneumatic cleaning system
  • Highly engineered safety equipment enables safe and reliable operation
  • All system components are built and supplied by a single provider for optimal system perfor­mance
  • Automatic ignition system elimi­nates conti­nuous burning and saves fuel (option – only for fuels with less than 40% water content)
  • Outstanding output regulation from 30 to 100%


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Example instal­lation

Local heating network

Firing system: Pyrtec
Output: 530 kW
Fuel: Natural chips

Anlagenbeispiel UF
  1. Fuel storage in a silo
  2. Fuel discharge with push rod
  3. Fuel transport with screw system
  4. Firing system: Pyrtec
  5. Ash removal from combustion chamber into 240 or 800 l container
  6. Flue gas dust removal with multi­cy­clone separator