Wood boilers with 150-500kW output

Boiler LUK-150, 200, 300, 500 is a three-tubed steel boiler for heating terraced houses, apartment blocks, production and municipal buildings.

LUK-type steel water boiler is intended for producing hot water in the heating systems of
residential buildings and production facilities.

The firebox and horizontal smoke tubes of theboiler aremade of Ø 76 mm pulled steel pipes. The fuel can be logs and coal; by adding a burner, grainleftovers, wood granules, pellets, wood and peat briquette, sawdust or wood shavings can be usedas well. The boilers have large service hatches and a spacious firebox that ensurea comfortable heating and easy cleaning. Ash isolation system and smoke turbulators and pneumatic cleaning system for convective parts are available as add-ons.

It is possible to changes the door handedness. The boiler set includes a thermo-manometer, pressure relief valve, ventilator, hook, broom.

Operating description of the boiler

All LUK-type boilers transfer the heat generated in the combustion chamber by convection to the boiler water through the steel walls of the boiler’s combustion chamber and flue gas pipes. Hot flue gases travel from the combustion chamber trough the lower flue gas pipes, the cleaning hatch slot and upper flue gas pipes to the flue gas duct, thus generating three flue gas passages. The optimal burning control is achieved by setting the primary and secondary air and changing the amount of fuel. The quality of burning can be visually assessed or measured by means of a gas analyser.

Used fuels

LUK-type boilers are intended for burning various solid fuels. The optimal work of the boiler is granted by using solid fuel with humidity level below 20%. The boilers are foremost intended for burning firewood, but they are also suitable for briquette and peat and with using burner, wood chips, pellet, industrial and agricultural residues are allowed to use.


  • Operating reliability: boiler’s well-thought structure ensures a lengthy durability
  • Universality: fuel can be logs, coal. By adding a burner, wood chips, grain leftovers, wood granules, pellets, wood and peat briquette, sawdust and wood shavings can be used for fuel.
  • Quality: the boiler is made of boiler steel and according to a standard EVS EN303-5:2012
  • Effectiveness: three fire tubes that ensure high efficiency and low smoke temperature
  • Comfort: large service hatches and spacious firebox that ensure a comfortable heating and easy cleaning
  • Tailor-made product according to a customer’s requests
  • Credibility: we have been producing boilers for over 20 years
  • Maintenance: being a domestic producer we guarantee that our products will operate from one year to another
  • Spare parts: immediate availability of spare parts ensures a complete functionality of the products
  • The boilers produced by Rapla Metall have the advantage of being universal regarding fuel that enables to provide the best overall solution of the heating system based on the customer’s needs!

1. Cleaning hatch
2. Secondary air regulator
3. Boiler door – filling hatch
4. Primary air regulator

5. Ash hatch
6. Chimney damper
7. Flue gas duct
8. Rear cleaning hatch

9. Insulation
10. Return inlet
11. Primary air ventilator connection
12. Safety valve connection 1”

13. Flow outlet
14. Temperature/pressure gauge
connection 1/2”
15. Water jacket
16. Combustion chamber

Nominal heat output kW 150 200 300 500
Efficiency with wood logs % 83
Main fuels
Wood logs, wood and peat briquettes
Efficiency with wood pellets % 90
Alternative fuels
Wood pellets, wood chips, grain and grain residues, sawdust, planer shavings
Boiler heating surface 8,5 11,0 18,6 23,0
Combustion chamber length mm 870 1190 1650 1200
Combustion chamber volume 0,44 0,60 1,04 1,11
Maximum operating water pressure bar 2,5
Test pressure bar 3,75
Minimum return water temperature ºC 60
Maximum operating water temperature ºC 95
Water volume of boiler liiter 280 390 580 930
Flow and return pipe connections DN65 DN80
Boiler weight kg 1300 1600 2100 2800
Building heated area 1800 2800 3800
Length A mm 1900 2150 2640 2220
Width B mm 990 990 1080 1440
Height C mm 2010 2010 2180 2440
Flue gas outlet height D mm 1565 1555 1675 1930
Flue gas outlet diameter mm Ø294 Ø294 Ø344 Ø400
Minimum chimney draught Pa 25
Recommended chimney cross-section cm² 1275
Recommended chimney height m 14
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