Wood-fired 20 to 110kW fuel boiler (biomass) WBS Active


1 449,80 € tax incl.


The wood-fired boiler with forced ventilation BURNiT WBS Active is made steel resistant, it is available in several powers going from 20 to 110 kW. It works with wooden logs, however, a burner with granules can be adapted in its lower door.

Made in Europe

Available on order

More details

More info

Boiler WBS Active

Product features


  • Electronic control unit controls the combustion by modulating the fan speed. Optional control of circulation pumps for central heating and domestic hot water (DHW).
  • Air feed fan optimizes the combustion and the fuel consumption rate.
  • Simple installation and handling.    
  • The water mantle embraces the combustion chamber in full to utilize the emitted heat most efficiently.
  • Combustion chamber with large heat exchanging surface and low chamber resistance.
  • Large firebox door ensures easy loading even with bigger logs (length of logs up to 50 cm).
  • Ribbed chamber surface and three-pass flue gas flow for improved heat exchange.
  • Exchangeable metallic ash grate protects the pipe grid from the flame.
  • Burner flange on lower door for fitting pellet, oil or gas burners (optional)

Boiler warranty : 2 years

Safety devices


  • STB - emergency thermostat - turn off the fan and stop the combustion process.
  • Pressure relief valve 3 bar;
  • Safety heat evacuator a tap-water-filled line passes through the upmost part of the boiler body. In case of overheating it is triggered open by a thermostatic valve (not included) to evacuate the heat of the boiler.
  • Air intake flap.


Boiler WBS Active chart

1. Control unit
2. Casing
3. High efficiency thermal insulation
4. Safety heat evacuator
5. Three-pass flue gas flow
6. Water mantle (jacket)
7. Combustion chamber
8. Metal ash grate
9. Ash- and- soot container
10. Burner flange (optional)
11. Flue
12. Air feed fan
13. Air intake flap


Technical specification

Boiler WBS Active chart



WBS Active
Nominal heat outputkW20253040506090110
Height Hmm12351235123512351235138513851385
Width L x Depth Dmm540 x 860540 x 925600 x 925700 x 925700 x 985700 x 1105760 x 1105820 x 1105
Water mantle volumeL60758296106134145162
Combustion chamber volumeL5862738497120133160
Required chimney draughtPa/mbar16 /0.1620/0.2021/0.2123/0.2324/0.2438/0.3847/0.4756/0.56
Insulation boilerHigh-efficiency thermal wool
Insulation doorsHigh-efficiency thermal wool
Average power consumptionW6060606060110110110
Electric power supplyV/Hz230/50230/50230/50230/50230/50230/50230/50230/50
Recommended fuelWood, humidity 20%, wood briquettes, wood+coals, wood+fruit pits / broken nuts
Loading door sizemm330 / 250330/250390/250490/310490/310490/310550/310610/310
Max. length of firewood logsmm400400500500500600600600
Operating temperature range°C65-8565-8565-8565-8565-8565-8565-8565-85
Min. return water temperature°C6060606060606060
Operating pressurebar33333333
Cold water inletA, mmR1¼"/232R1¼"/232R1¼"/232R1¼"/232R1¼"/232R1½"/232R1½"/232R1½"/232
Hot water outletB, mmR1¼"/1265R1¼"/1265R1¼"/1265R1¼"/1265R1¼"/1265R1½"/1420R1½"/1420R1½"/1420
Sleeve for sensor of safety valveK, mmG½"/1075G½"/1075G½"/1075G½"/1075G½"/1075G½"/1225G½"/1225G½"/1225
Safety heat evacuator inlet/outletE, mmR½"/1072R½"/1072R½"/1072R½"/1072R½"/1072R½"/1220R½"/1220R½"/1220
FlueF, ø / mmø150 / 945ø150 / 945ø150 / 945ø180 / 930ø180 / 930ø200 / 1065ø200 / 1065ø200 / 1065
J, mm270270300350350350380410
Flue cleaning openingO, mm150/70150/70150/70150/70150/70150/70150/70150/70
DrainY,mmG½" / 232G½" / 232G½" / 232G½" / 232G½" / 232G1" / 232G1" / 232G1" / 232
Air intake flapV, mm215215215215215215215215
J, mm270270300350350350380410
Air intake fanW, mm215215215215215215215215
Burner flange (optional)Z, ø mm176176176176176176215215
Ash-and-soot containerXYes


For product measurements, they should be read as follows:

Cold water inletA, mmR1¼ "/ 450
Y, mmmG½ "/ 232

A is shown in the previous diagram. "R1¼" and "G½" are the measure in inches of the opening. "R" is male and "G" is female. The measurements in inches indicate the distance between the floor and the opening.

Recommended clearances between the boiler and walls

Burnit WBS Active

Relation between wood heating value and water content

Burnit WBS Active

Boiler size and chimney parameters

Burnit WBS Active

Connecting the safety heat exchanger

Burnit WBS Active

1. Water supply network (pressure 6-10 bar)
2. Drainage (sewerage)
3. Boiler WBS Active
4. Safety heat exchanger inlet
5. BVTS valve sensor
6. Safety heat exchanger outlet

Connection of controller ST-81

Burnit WBS Active

Connection of BURNiT WBS Active boiler to three-way valve

Burnit WBS Active

Connection of BURNiT WBS Active boiler to P type buffer tank and three-way valve

Burnit WBS Active 

Connection of BURNiT WBS Active boiler to combi tank KSC2, flat plate solar collector PK and three-way valve

Burnit WBS Active

Connection of BURNiT WBS Active boiler to solar tank SON, buffer thank P, flat plate solar collector PK and three-way valve

Burnit WBS Active