Atmos Combi C 20 S, 25kW


Availability: In stock

SKU: 0000002687

Gasification solid fuel boiler with electro-mechanical control Atmos Combi C 20 S for central heating of premises. Constructed for solid fuel burning - wood and coal.

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Product Description

The ATMOS gasifying boilers are constructed for burning wood and coal on the principle of generator gasifying with the use of a gas exhaust ventilator, which withdraws the combustion gases from the boiler, or leads air into the boiler.

The boiler body is produced as a weldment of 3-8 mm steel sheets. The boiler consists of two chambers, one placed upon the other. The upper chamber makes up the fuel container, and the lower one, combustion chamber and ash collector. Between the two chambers, a new rotating, patent protected grate is placed. The grate ensures perfect combustion of coal, wood, or a combination thereof, as well as simple cleaning. The burnout part of the multiple chamber furnace under the fuel hopper is equipped with ceramic pipe fittings. There is a vertical combustion gas duct in the back of the boiler body, which is equipped with a heating valve in the upper section. The upper part of the combustion gas duct is fitted with a gas exhaust outlet for connection to a chimney.

Product features

  • Burning coal and wood separately, we recommend together.
  • Revolving furnace grate for easy ash removal.
  • Secondary air is preheated to a high temperature – higher effectiveness.
  • The ventilator automatically switches off when the fuel burns out.
  • Easy servicing and cleaning.
  • Ceramic combustion space – high effectiveness.
  • Large fuel container.
  • Large space for ash.
  • Boiler without tube plate – easier cleaning (except C 50 S).
  • Small size and low weight.
  • High quality.


Reverse combustion and a ceramic combustion chamber enable perfect combustion with minimum polluting emissions. The boilers comply with environmentally friendly product requirements according to Guideline No. 13/2002 of the Czech Ministry of Environment. They comply the European Standard EN 303-5 and all the boilers rate in class 4.


ATMOS boilers must be connected via the LADDOMAT 21 or ESBE thermoregulation valve to achieve keeping the minimum temperature of water returning to boiler at 65οC. The temperature of water exiting the boiler must be permanently kept between 80-90οC. The default configuration of all boilers includes a cooling circuit to prevent overheating. We recommend installing boilers with accumulation tanks.


All ATMOS boilers are certified in testing laboratories for the individual countries of destination: State Testing Laboratory Brno, TÜV Munich-Germany, Lithuania, Ukraine, Sweden, Poland, Austria, Slovakia, Hungary according to current standards EN 303-5. Protected by patent. 


Power is controlled with a safety valve operated with the draught regulator, FR 124 type, which automatically opens or closes the safety valve according to a set output temperature of water (80 - 90°C), except for DC50SE which is equipped with a BELIMO servo flap with a spring. When setting the power regulator, much attention should be paid because the regulator has another important function other than power regulation - it also secures the boiler against overheating. A controlling thermostat located on the boiler panel regulates the fan according to a set temperature (75 - 85°C). A temperature lower by 5°C should be set on the controlling thermostat rather than on the FR 124 draught regulator.
The boiler runs at a reduced output even without a fan - heating is not lost when the electric power fails. At up to 70 percent of its rated output, the boiler can be operated without a ventilator.

Atmos standart controller

Panel composition:
Main off switch, safety thermostat, thermometer, regulator thermostat and combustion thermostat

Electro-mechanical regulation is an optimum solution for easy management of the operation of the boiler (ventilator).

The design of the panel with standard regulation is a basic design for all produced boilers.


Atmos combi schematic


1. Boiler drum 14. Fireproof and heat-resisting fitting - GS - rear face of round space
2. Filling door 15 Cleaning cover
3. Ash pan door 16 Furnace grate level
4. Ventilator - pressure, exhaust (S) 17 Firing safety valve pull rod
5. Fireproof and heat-resisting fitting - rear block 18 Thermometer
6. Control panel 19 Furnace curtain - front
7. Safety thermostat 20 Switch
8. Regulating safety valve 22 Power regulator - Honeywell FR124
9. Grate bar 23 Fireproof and heat-resisting fitting - front block
10. Fireproof and heat-resisting fitting - round space L + P 24 Ventilator thermostat
11. Furnace grate tube 25 Door panel - Sibrall
12. Fireproof and heat-resisting fitting - half-moon 26 Door sealing - cord 18 x 18
13. Firing safety valve 27 Waste gas thermostat
    32 Cooling loop

Additional Information

2 Years

Weight (kg)

Country of Manufacture
Czech Republic

Product Brand

Heat output (kW)

Range of heat output (kW)
17 - 25

Dimension Depth (mm)

Dimension Width (mm)

Dimension Height (mm)

Efficiency (%)

Construction material

Mantle volume (L)

Operating temperature range (°C)
65 - 90

Min. return water temperature (°C)

Recommended fuel
Brown coal of walnut size with specific energy 17-20 MJ/kg; dry wood with specific energy 15-18 MJ/kg, diameter 70-90 mm, 12 - 20% moisture level

Maximum length of the firewood logs (mm)

Flue (mm)

Required chimney draught (Pa)

Fume extraction device

Exhaust Location
Back side

Control panel

Control of central heating pump

Electric power supply (V/Hz)

Power consumption (W)

Thermostatic draught regulator
Yes, FR124



Class of boiler according to EN 303-5

Cold water inlet
J : 1 1/2"

Hot water outlet
J : 1 1/2"

Distance of hot water outlet
CH : 212

Height of Hot Water Outlet
G : 210

Cooling loop

Overheating protected

Firing safety valve

Firing safety valve pull rod

Height of Flue Pipe
D : 1121

Height of Return Water Pipe
H : 1177

Door sealing
Cord 18 x 18

Ash and soot container

Files & Manuals

View FileATMOS CE Certification EN    Size: (229.15 KB)