• Automatic wood ignition
  • Technical details

Wood gasification boilers – Dokogen

Modern Dokogen boilers are characterized by a unique combustion chamber, which is lined on both sides with ceramic fittings. These fittings are provided with openings in the lower part for the supply of highly preheated primary air, which ensures the gradual wood pre-drying and combustion. Between the upper combustion chamber and the lower combustion chamber, the boilers are equipped with a gasification nozzle with openings for the supply of preheated secondary air. Through this nozzle, the flames go into the lower combustion chamber with a spherical ceramic space, where all combustible substances are completely burned. The boilers are also equipped with a rear flue gas duct with a tube heat exchanger, ensuring the highest boiler efficiency, and an exhaust fan which function is to blow flue gases into the chimney. The ATMOS Dokogen boiler body is made as a weldment from high-quality steel sheets with a thickness of 3 to 8 mm.

Wood gasification (reverse combustion) with subsequent combustion of wood gas at temperature between 1000 and 1250 °C in a ceramic combustion chamber guarantees high-quality wood combustion with high efficiency and a minimum of harmful exhalations.

The air supply and combustion process controlled by the exhaust fan, together with simple or electronic controller according to the customer’s needs, allow the boiler to heat up quickly and burn well from the ignition.

  • Boiler efficiency according to type 90,3 - 92,5 %

  • Meets the requirements for Ecodesign (2015/1189)

  • Boiler class 5 (ČSN EN 303-5)

Advantages of wood gasification boilers ATMOS

  • Option to burn large pieces of wood
  • Large space for wood – long burning time – up to 12 hours, depending on boiler type
  • Tube heat exchanger
  • High efficiency over 90 % – primary and secondary air is preheated to a high temperature
  • Ceramic loading chamber – fuel pre-drying
  • Ceramic combustion chamber
  • Ecological burning – boiler class 5 – EN 303-5:2012, ECODESIGN 2015/1189
  • Exhaust fan – dust-free ash removal, smokeless boiler room
  • Cooling loop protecting against overheating – without risk of boiler damage
  • Automatic shutdown of the boiler after the fuel burns out – flue gas thermostat
  • Comfortable ash removing – large space for ash (when burning wood, clean it 1x / week)
  • Small size and low weight
  • Possibility of choosing a door R / L (right/left) for selected types
  • High quality


ATMOS boilers must be connected via the LADDOMAT 22 or thermoregulatory valve (three-way valve controlled with actuator) to achieve keeping the minimum temperature of water returning to boiler at 65 °C. We keep the outlet temperature of the boiler in the range of 80 – 90 °C and set the temperature of the water to the radiators or floor heating on the mixing three-way valve as needed (e.g. 30 – 80 °C).
The default configuration of all boilers includes a cooling circuit to prevent overheating. We recommend installing a boiler with accumulation tanks, which will reduce fuel consumption and increase heating comfort.


Boilers regulation

Electromechanical regulation – boiler performance is regulated by an air regulating valve controlled by a draft regulator, FR 124 type, which automatically opens or closes the air valve according to the set water outlet temperature (80 – 90 °C). In addition to performance regulation, the draft regulator helps protect the boiler against overheating. Its advantage is a quick ignition and firing up to the required output when the air valve is fully open. The boilers are equipped with a control thermostat on the instrument panel, which controls the exhaust fan according to the set water outlet temperature (80 – 85 °C) and a flue gas thermostat, which is used to shut down the boiler and turn off the exhaust fan after the fuel has burned out. In the case of connecting a boiler with accumulation tanks, the flue gas thermostat also controls the operation of the pump in the boiler circuit.

The advantage of regulation and design of ATMOS boilers is that the boilers work with a good chimney draft up to 70 % of the nominal power even without a fan.

Panel composition:
Main switch, safety thermostat, thermometer, control thermostat and flue gas thermostat.

Electromechanical control is the optimal solution for controlling the operation of the boiler (fan) in a simple way. The design of the panel with standard regulation is the basic design for all manufactured boilers.


Equithermal regulation ACD 03

Each boiler can be equipped with a modern touch electronic control ATMOS ACD 03 for controlling the entire heating system depending on the outdoor temperature, room temperature and time. This regulation is able to control the boiler itself with a fan with many other functions.


Equithermal regulation ACD 04

The boilers DC18GD, DC25GD and DC30GD can be ordered from the factory with built-in ATMOS ACD 04 touch screen control only with with combination with Automatic wood ignition (AIW).The boilers are factory-equipped with all the necessary sensors for connecting the boiler and the heating system, including the flue gas temperature sensor (AGF). This unit is designed for comfortable control of the hot water system of the heated building. The controller contains functions for direct control of the boiler, boiler circuit, three heating circuits, domestic hot water, solar, etc.

Automatic wood ignition

Automatic wood ignition is used for the planned ignition of the boiler, eg before the arrival home in the afternoon or before arrival at the cottage. Ignition of the fuel is very fast (approx. 5 minutes) and allows the boiler operator to arrive “into the heat”. Fuel ignition can be set and scheduled to control ATMOS ACD 04 according to time (weekly program), according to the requirements of the heating system or according to the temperature in the Accumulation tank.

A device for automatic wood ignition is built in between the upper and lower doors (a chamber with a heating spiral). High-quality wood pellets are used for ignition, which are used to fill the ignition chamber. The amount of pellets corresponds to the size of the shovel that is included in the delivery of the boiler.
The pellets are ignited at the set moment using an electric heating spiral (500 W).


Drawings of boilers with automatic wood ignition Drawing of the ignition device
1. Boiler body 19. Intake duct – air duct 1.  Ignition spiral plate
2. Stocking door (upper) 20. Main switch 2.  Ignition spiral
3. Ash-pan door (lower) 22. Draught regulator – Honeywell FR 124 3.  Removable ignition chamber
4. Exhaust fan 23. Cooling loop protecting against overheating 4.  Screw lid (always tightened during operation)
5. Heatproof shaped piece – nozzle 24. ATMOS ACD 04 controller 5.  Removable blanking chamber
6. Control panel 25. Door filling – Sibral
small – thick for upper door
small – thin for lower door
6.  Pellet filling scoop
7. Safety thermostat 26. Door sealing – cord 18 x 18
8. Regulating flap 30. Capacitor for exhaust fan – 1μF
9. Heat proof shaped piece – for type GD
– combustion area side)
33. Tube heat exchanger (tubular)
10. Heat proof shaped piece – for type GD
– spherical space
35. Pocket for thermostats (sensors)
11. Sealing – nozzle – 12 x 12 (14 x 14) 36. Locking screw
12. Heatproof shaped piece – half moon  37. Ignition device
13. Ignition valve
14. Heat proof shaped piece – for type GD
– rear face of spherical space
K flue gas duct neck
15. Cleaning lid L water outlet from
16. Frame shield M boiler – water inlet to
17. Ignition valve pulling rod N boiler – filling valve
18. Fuse T6,3A/1500 – type H P pipe sleeve – sleeve for cooling loop control valve sensor (TS 131, STS 20)

Technical details


Description of the boiler drawing
1. Boiler body 18. Thermometer
2. Filling door – upper 19. Supply air duct
3. Ashtray door – lower 20. Switch with an indicator light
4. Exhaust fan (S) 22. Draught regulator – HONEYWELL FR124
5. Heat-resistant fitting – nozzle 23. Cooling loop protecting against overheating
6. Control panel 24. Fan control thermostat (boiler)
7. Safety thermostat 25. Door panel – Sibral
8. Control flap 26. Door seal – cord 18 x 18
9. Heat-resistant fitting – side part 27. Waste gas thermostat
10. Heat-resistant fitting – spherical space L + R 30. Capacitor for exhaust fan
11. Nozzle seal – 12 x 12 (14 x 14) 33. Tube heat exchanger – tube sheet
12. Heat-resistant fitting – half-moon  
13. Firing up valve K  – the flue-gas duct neck
14. Heat-resistant fitting – rear part of spherical space L  – the boiler water outlet
15. Cleaning lid M  – the boiler water inlet
16. Frame screen N  – filling valve pipe sleeve
17. Fire valve stem P  – sleeve for a sensor of the valve which regulates the cooling loop


Boiler dimensions (mm) Boiler type
A 1281 1281 1281 1435 1435
B 820 1020 1020 1120 1120
C 680 680 680 680 680
D 945 945 945 1095 1095
E 150/152 150/152 150/152 150/152 150/152
F 87 87 87 82 78
G 185 185 185 185 185
H 1008 1008 1008 1152 1152
CH 256 256 256 256 256
I 256 256 256 256 256
J 6/4″ 6/4″ 6/4″ 2″ 2″


Specifications Boiler type
Boiler heat output kW
19 25 29,8 40 49
Boiler thermal input kW 20,8 27 32,6 44 53,3
Heating surface m2 2,5 3,1 3,1 3,8 4,1
Fuel shaft volume dm3 (l)
80 120 125 160 160
Filling hole dimensions mm 450 x 260 450 x 260 450 x 260 450 x 260 450 x 260
Prescripted chimney draft Pa/mbar
16/0,16 18/0,18 20/0,20 22/0,22 24/0,24
Max. working water overpressure kPa/bar 250/2,5 250/2,5 250/2,5 250/2,5 250/2,5
Boiler weight kg
376 469 466 548 565
Gas-outlet pipe diameter mm 150/152 150/152 150/152 150/152 150/152
Ingress protection of electric parts IP 20 20 20 20 20
Electrical power input (auxiliary) W 50 50 50 50 50
Electrical input in standby mode W 0 0 0 0 0
Ignition mode   manual / automatic manual
Efficiency over the entire performance range %
91,5 92,5 91,3 90,6 92,0
Boiler class   5 5 5 5 5
Boiler category   1
Operating mode   non-condensing
Energy efficiency class   A+ A+ A+ A+ A+
Waste gas temperature at nominal output °C 145 127 148 175 183
Waste gas combustion products flow weight at nominal output kg/s 0,014 0,017 0,017 0,021 0,025
Specified fuel (preffered)   Dry wood with a calorific value of 15 – 17 MJ/kg-1, water content 12 – 20 %, diameter 80 – 120 mm
Average fuel consumption for the heating season kg.h-1 5,1 6,1 7,7 10 13
Prescribed wood length mm
330 530 530 530 530
Combustion time at nominal output Hours 2 2 2 2 2
The volume of water in the boiler l
73 105 105 112 128
Boiler hydraulic loss mbar  0,22 0,22 0,22 0,23 0,24
Minimum volume of accumulation tank l 1045 1375 1639 2200 2695
Regulation temperature settings °C from 75 to 95
Connecting voltage V/Hz  230/50
Minimum return water temperature during operation °C 65
All boilers in DOKOGEN line are only intendet for connection with an ACCUMULATION TANKS of sufficient capacity with a minimum of 55 litres per 1 kW of instaled boiler output.