BURNiT WBS Active 70, 70kW

Solid fuel boiler with fan-assisted combustion Burnit WBS Active 70 for central heating of premises up to 410m². Constructed for solid fuel burning - wood, wood briquettes class B and coal.

€2,034.00 €1,695.00
Availability: In stock

Steel boiler with intelligent electronic controller and electric fan for forced air feed. Solid fuel boilers WBS Active range in nominal output from 20 to 110 kW to satisfy the heating demands of medium to large sized spaces. They are engineered for burning solid fuel - wood, wood briquettes class B and coal, and provide the option for fitting pellet, oil or gas-fired burners.


The boiler body is manufactured from high quality steel with 5mm thickness for the combustion chamber and 3mm thickness for the water mantle. The combustion chamber has a large heat exchanging surface and low chamber impedance. Large firebox door ensures easy loading even of large chunks of wood.

Controller ST-81

ST–81 temperature regulator is intended for controlling central heating boilers. It controls the water circulation pump, domestic hot water pump and the fan. Four optional modes of the pumps operation: house heating, boiler priority, parallel pumps, summer mode. The controller's casing is designed to be mounted to the boiler installation. Its functions are based on data from sensors. The electronic control unit regulates the burning process with the blower, based on the fuel used and the chimney draught, allowing for a wide range of operation.


To increase the heat exchange, the combustion chamber's surface is ribbed and designed for a three-pass flue gas flow. The mantle completely envelops the firebox for maximized usage of the heat. The boiler's body is insulated from the external conditions by 50mm thick high temperature resisting wool.

Safety devices

For a safe and reliable operation of the boiler, a number of safety devices are installed

- Removable metallic ash grate protects the heat exchanging pipes and the chamber base from the flame

- Pressure relief valve 3 bar incl.in the delivery set

- Safety heat evacuator: a tap-water filled line passes through the uppermost part of the boiler body. In case of overheating it is triggered open by a thermostatic valve (not included) to evacuate the heat off the boiler.


The central heating boiler can operate with natural untreated wood, but also with coal and compressed solid fuel such as briquettes. Maximum length of the wood logs is between 330mm and 500mm depending on the model. Fuel moisture should be 20% or lower.

In order to use the maximum caloricity of the fuel, the wood logs should be dried for a prolonged period of time. High moisture levels reduces caloricity and the output power of the boiler.


This series of boilers is manufactured for burning solid fuel, with the option of adaptation to a different kind of fuel. This is possible by mounting a pellet, gas or an oil burner on the lower door opening. A flange is also needed to mount the burner (optional).

Schematic of the main features of a WBS Active wood boiler




1. Control unit
2. Casing
3. High efficiency thermal insulation
4. Safety heat evacuator
5. Three-pass flue gas flow
6. Mantle
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

This appliance complies with EN 303-5.

More Information
Warranty 1 year electronic components, 2 years on the boiler
Weight (kg) 368.0000
Country of Manufacture Bulgaria
Heat output (kW) 70
Approximate heating surface (m²/ft²) 250-410
Approximate heating capacity (m³) 1107
Dimension Depth (mm) 1225
Dimension Width (mm) 730
Dimension Height (mm) 1470
Loading door size (Height, Width), mm 310/ 490
Construction material Steel
Mantle volume (L) 141
Insulation boiler high efficiency thermal wool
Insulation doors high efficiency thermal wool
Combustion chamber volume (L) 120
Combustion chamber impedance (Pa/mbar) 41/ 0.41
Combustion viewer No
Pellet burner No
Operating pressure (bar) 3
Operating temperature range (°C) 65-85
Maximum water temperature (°C) 95
Min. return water temperature (°C) 60
Recommended fuel wood, humidity 20%, wood briquettes ; coal
Fuel Type Wood, Briquettes, Coal
Maximum length of the firewood logs (mm) 600
Flue (mm) 200
Required chimney draught (Pa/mbar) 38/ 0.38
Flue cleaning opening O : 150/70 mm
Exhaust gas temperature (operation mode), °C <150
More Information
Exhaust Location Back side
Lambda sensor No
Flue gas temperature sensor No
Control panel U: Yes
Control unit ST - 81
Control of central heating pump Yes
Remote control No
Electric power supply (V/Hz) 220/ 50
Average power consumption (W) 45
Combustion forced ventilation Yes
Automatic cleaning system No
Thermostatic draught regulator No
Certification CE
Cold water inlet A : G 2''/ 135 mm
Hot water outlet B : G 2''/ 1380 mm
Distance of hot water outlet J : 365 mm
Height of Hot Water Outlet B : 1380 mm
Cooling loop Yes
Safety line sleeve K : G 3/4'' / 1240 mm
Safety heat evacuator inlet/outlet E : R 1/2'' / 1210 mm
Air fan supply W : 277mm
Air intake flap V : 277 mm
Height of Flue Pipe F: 1055 mm
Height of Water Drain Valve Y : 110 mm
Drain Y : G 1''
Burner flange (optional) Z : 176 mm
Ash and soot container X : Yes
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