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Basic conditions for good function and long life of ATMOS boilers

  • the boiler is installed only by a professional company trained by the manufacturer
  • the boiler must be installed in a dry and well-ventilated area – the boiler room
  • when connecting the boiler to the system, it is always necessary to install Laddomat 22 behind the boiler, or thermoregulation valve TV 60/65/70/75 °C with pump, ball valve and filter, so that the temperature of water returning to the boiler, in each mode, does not fall below 65 °C – according to standard ČSN 070240/93. As the temperature of the return water to the boiler increases, the possibility of acid tar condensation decreases = longer boiler life. We recommend Laddomat 22 for outputs of 15 – 100 kW.
  • when connecting a boiler without storage tanks, the pump in the boiler circuit and in the circuit of the heated object must be switched by one or two separate thermostats at the boiler leaving water temperature of 70 – 80 °C so that the pump runs in the heated object circuit only when running pump in the boiler circuit. The reason is that the boiler is not subcooled via the non-return valve built into the Laddomat 22.
  • in each boiler mode, the boiler leaving water temperature must be between 80 – 90 °C.
  • if the boiler is operated continuously at an output lower than 40% of the nominal output or for domestic hot water heating in summer, it is necessary to heat daily due to the life of the boiler. It is not possible to operate the boiler permanently in attenuation, as tars and acids can be formed, which damage the boiler body.
  • the boiler must be protected against overheating in the event of a power failure, as it has a certain inertia.
  • maximum working water overpressure in the boiler – 250 kPa (2.5 bar).

Connection without storage tanks

One of the main disadvantages of connecting a boiler without storage tanks is the need to add fuel to the boiler more often. In the case of a permanently inhabited building and the boiler connection without storage tanks, it is necessary to heat the boiler every day. Another no less important fact is the reduction of the boiler life, in contrast to the connection of the boiler with the storage tank, where we can extend the life of the boiler up to twice.

Connection with accumulation tanks

Installing a boiler with storage tanks brings the following advantages:

  • lower fuel consumption (by 20 to 30 %), the boiler works at full capacity up to fuel burn-up at optimum efficiency
  • high service life of the boiler and chimney – minimal formation of tars and acids
  • possibility of combination with other methods of heating – electric heating/solar energy
  • designed for combinations of radiators with underfloor heating
  • comfortable heating and ideal fuel combustion
  • guaranteed more environmentally friendly heating
  • warranty on the boiler body 3 years


We recommend connecting with accumulation tanks as the main connection
If you cannot have the recommended volume of storage tanks, connect the boiler with at least one buffer tank with a volume of 500 – 1000 l. The installation of the heating system must be performed by a professional company according to valid standards. If you choose a large volume of the storage tank, you must also select the appropriate boiler output to be able to charge these tanks in a reasonable time.

Operation of the system with accumulation tanks
After ignition, we run the boiler to the maximum (nominal) output and charge the given volume of storage tanks to the required water temperature of 90 – 100 °C for 2 to 4 loads. Then we let the boiler burn out. Furthermore, we only take heat from the storage tank with the help of a three-way valve for a time that corresponds to the size of the battery and the outdoor temperature. During the heating season (observing the minimum battery volumes, see the table) this can be 1 – 3 days. If the prescribed storage volume cannot be installed, we recommend at least one tank with a volume of 500 – 1000 l for balancing boiler starts and stops.

Tank insulation
Accumulation tanks are normally supplied with insulation. In the case of purchasing a tank without insulation, a suitable solution is the joint insulation of a given number of tanks of the required volume with mineral wool into a plasterboard skeleton, or additional filling with loose insulation. Recommended insulation thickness, when using mineral wool is 120 mm. Another option is to purchase already insulated tanks with mineral wool in a leatherette case, which our company also supplies.

DHW heating
You can use a combined boiler or a accumulation tank with a copper instantaneous heater or a floating boiler to heat domestic hot water.


Recommended volume of accumulation tanks

Minimum accumulation tank volume
Output / kW 20 22 25 35 / 32 40 49 70 99
Volume / l 1000 – 1500 1500 – 2000 1500 – 2000 2000 – 2500 2500 – 3000 3000 – 4000 4000 – 5000 5000 – 6000


Tank specification

Tank type Volume (l)   Diameter (mm) Height (mm)
AN 500 500 600 1970
AN 600 600 750 1611
AN 750 750 750/790* 2010/1750*
AN 800 800 790* 1910*
AN 1000 1000  850/790* 2065/2210*

*type DH

The tanks are supplied without insulation or with insulation in a leatherette case.


Minimum pipe diameters when connected to accumulation tanks

Minimum pipe diameters when connected to accumulation tanks
part A part B
Boiler output
in copper in steel in copper in steel
10 – 30 kW 28 x 1 25 (1″) 28 x 1 25 (1″)
31 – 45 kW 35 x 1,5 32 (5/4″) 28 x 1 25 (1″)
46 – 65 kW 42 x 1,5 40 (6/4″) 35 x 1,5 32 (5/4″)
70 – 150 kW 54 x 2 50 (2″) 42 x 1,5 40 (6/4″)

Boiler circuit fittings

Laddomat 22

– is designed for boilers with an output from 15 to 100 kW

We recommend connecting higher output boilers with a thermoregulation valve and a powerful pump or a three-way valve controlled by an actuator with electrical regulation maintaining a minimum return water temperature of 65 – 75 °C. When connecting a boiler with storage tanks, we can use an open or closed expansion vessel.

Thermoregulation valves

Thermoregulation valve type TV 60 °C (65/70/72/77 °C) is used for solid fuel boilers. At a boiler water temperature of + 60 °C, the thermoregulation valve opens and liquid from the circuit of the heated object is introduced into the boiler circuit. In this way, the minimum return water temperature to the boiler is ensured. If necessary, it is possible to use a thermoregulation valve set to a higher temperature (eg 72 °C).

Recommended size of thermoregulation valve TV 60 °C (65/70/72/77 °C)
15 kW ― 30 kW – DN25
30 kW ― 45 kW – DN32
45 kW ― 150 kW – DN40 – DN50


Original ATMOS Connection

This is a professional stainless steel connection manufactured by the ATMOS company designed to maintain the minimum temperature of the return water to the boiler and to quickly connect the boiler using two screw connections with a flat seal. The connection contains all the necessary components required by the manufacturer (safety valve 2.5 bar, venting valve, manometer, two pumps, two shut-off valves, three-way valve and, for variants F3 and F4, two servo drives). The connection is ready for connecting the boiler directly to the heating system or for connecting the boiler with storage tanks. The connection allows for a larger heating system to be expanded to two or three heating circuits by using a special distributor and the necessary pump group.
In the case of boilers of the DxxP Compact series Automatic pellet boilers, this Connection is part of the boiler.

Overview Connection of ATMOS boilers
Connection ATMOS
F1 Laddomat
Connection ATMOS
F2 Laddomat
Connection ATMOS

Connection ATMOS
Connection ATMOS
Connection ATMOS
F15 – 16 ESBE-PX
F1 (15 – 30 kW)
for boilers:

DC18S, DC22S, DC22SX, DC25S, DC30SX,
C15S, C18S, AC16S, AC25S
F2 (15 – 40 kW)
for boilers:

DC32S, DC40SX, DC15GS, DC20GS,
F3 (15 – 30 kW)
for boilers:

DC18S, DC22S, DC22SX, DC25S,
DC30SX, C15S, C18S, AC16S, AC25S
F4 (15 – 40 kW)
for boilers:

intended for the same types of boilers as for Connections F1 – F4,
each time with a different combination of pipes
see more info here
for boilers:
F15 – D10PX
F16 – D15PX, D20PX, D25PX

In combination with the PSC 25 – 35 pipe extension set, the F2 Connection can be used for C25ST and C32ST boilers.
In combination with the PSC 40 – 50 pipe extension set, the F2 Connection can be used for C40S and DC40GS boilers.


Connection ATMOS F1 – F2 Laddomat

Connection ATMOS F3 – F4 ESBE

Connection ATMOS F15 – 16 ESBE-PX

Connection ATMOS F12

Boiler DxxP Compact

Boiler overheating protection

  1. the boilers are equipped with a cooling loop against overheating as standard and can be connected with a valve TS 131 3/4 ZA (95 °C) or WATTS STS 20 to the water supply system (in case of our own well we will use other variants)
  2. backup power supply energy (battery) per pump
  3. one part in the system is connected to the spontaneous circulation of water with several radiators
  4. boiler connected with aftercooling tank and inverse zone valve, which without el. current opens

Connecting the cooling loop
Valve whose sensor is located at the rear of the boiler protects it against overheating so that if the water temperature in the boiler rises above 95 °C, it lets water from the tap into the cooling loop a line that takes in excess energy and goes to waste. In the case of placing a non-return valve on the water inlet to the cooling loop, in order to prevent possible backflow of water, due to pressure drop in the water supply system, we must equip the cooling loop with a safety valve 6 – 10 bar or an expansion vessel with a volume of at least 4 l.

Caution – the overheating cooling loop must not be used in accordance with EN 303-5 for purposes other than overheating protection (never for domestic hot water heating).


Using a Backup electricity source
You can use the backup source in case of power outage and you need to drive the circulation pumps in the heating system. We recommend connecting ATMOS circulation pumps and boilers to so-called backup sources with a sinusoidal voltage curve – Sinusoid.

What battery capacity to choose?
Find out its power consumption (e.g. 20 W) on the pump’s nameplate. To calculate the required current (A), we divide Power (W) by Voltage (V). So, there is an example if we have a 12V battery, the calculation would be 20 W / 12V = 1.67 A.

If there is a need to Backup the circulation pump for approx. 5 hours (average fuel burning time at full load), we multiply the consumed current and the backup time, 1.67 x 5 = 8.3Ah. However, when dimensioning, it is better to count on a 20% reserve. You therefore need a battery with a capacity of at least 10Ah to back up such a pump. With the recommended connection of ATMOS boilers, at least two circulation pumps are required, this must be taken into account when calculating the battery capacity and purchasing the given backup source.
The above procedure serves as an example for the calculation.

Boiler room 

Boilers must be located in a boiler room to which sufficient access to the air needed for combustion is ensured. Placing boilers in the living space (including corridors) is not permitted. The cross-section of the opening for the supply of combustion air to the boiler room must be at least 350 cm2 for boilers with an output of 15 – 150 kW. We recommend making a concrete (metal) base with the recommended dimensions under the boiler, see the instructions for your boiler. We also recommend underlaying the rear part of the boiler by about 10 mm.





Combustion path

Smoke flue
The flue must open into the chimney flue.If it is not possible to connect the boiler to the chimney vent directly, the relevant flue extension should be as short as possible, but no longer than 1 m, without an additional heating surface and must rise towards the chimney. The flues must be mechanically strong and tight against the penetration of flue gases and can be cleanable inside. Flues must not be routed by other residential or utility units. The inner cross-section of the flue must not be larger than the inner cross-section of the flue and must not narrow towards the chimney. The use of smoke knee pipes is not appropriate. Methods of flue penetrations through structures made of flammable materials are listed in Annexes 2 to 3 of ČSN 061008 and are particularly suitable for mobile houses, wooden huts, etc.

In case of a large chimney draft, install a draft regulator or a throttle valve in the flue.

Connecting the appliance to the chimney vent must always be done with the consent of the relevant chimney company. The chimney vent must always develop sufficient draft and reliably discharge the flue gases into the open air, for all practically possible operating conditions. For the boilers to function properly, it is necessary for the separate chimney vent to be correctly dimensioned, as the combustion, performance and service life of the boiler depend on its draft. The draft of the chimney directly depends on its cross-section, height and roughness of the inner wall. No other appliance may be connected to the chimney to which the boiler is connected. The diameter of the chimney must not be smaller than the outlet on the boiler (min. 150 mm). The draft of the chimney must reach the prescribed values. However, it must not be extremely high, so as not to reduce the efficiency of the boiler and not to disturb its combustion (not to break the flame). In the event of a large draft, install a throttle valve (draft limiter) in the flue between the boiler and the chimney.

Informative values of the dimensions of the chimney cross-section:
20 x 20 cm height 7 m
Ø 20 cm height 8 m
15 x 15cm height 11 m
Ø 16 cm height 12 m
The exact determination of the dimensions of the chimney is determined by the ČSN 73 4201 standard.

Attention – The chimney must be well sealed and insulated so that water vapor and tars do not condense in the chimney when the boiler output is reduced.


Draft regulator
Chimney draft must reach the prescribed values (13 – 35 Pa depend on the boiler type)

  • A small chimney draft shortens the life of the boiler – the boiler tars more, becomes clogged and smokes into the boiler room when adding fuel
    solution: lining the chimney, or place a special extension or exhaust fan on the chimney
  • High chimney draft increases fuel consumption. Higher chimney loss – lower boiler efficiency – poor combustion – the boiler may not achieve the required output
    solution: in case of a large chimney draft, install a draft regulator or a throttle valve in the flue

Fuel types


We recommend burning quality dry chipped log wood with a diameter of 80 – 150 mm, lengths of 250 – 1030 mm (depending on the type of boiler) with a humidity of 12 % to 20 % and a calorific value of 15 – 18 MJ.kg-1.

You will ensure maximum performance and long life of the boiler if you burn wood for at least 2 years. The following graph shows the dependence of the water content on the calorific value of the fuel. The useful energy volume in wood decreases very significantly with water content.


For example:
Wood with 12 – 20 % water has a heat value of 4 kWh / 1 kg of wood
Wood with 50 % water has a heat value of 2 kWh / 1kg of wood

Fresh wood heats little, burns poorly, smokes heavily and significantly shortens the life of the boiler and chimney. Boiler output will drop to 50% and fuel consumption will double.



The prescribed fuel for our boilers is quality brown coal OŘECH 1 with a calorific value of 17 – 20 MJ.kg-1.

The alternative fuel is a cube or briquettes. We recommend burning less sintering and low-sulfur coal. Smaller-grained fuel can only be added to the hot layer and in small quantities.





The prescribed fuel for our boilers is OŘECH 1 coal with a calorific value of 17 – 30 MJ.kg-1.

The alternative fuel is a cube or briquettes. We recommend burning less sintering and low-sulfur coal. Smaller-grained fuel can only be added to the hot layer and in small quantities.





The prescribed fuel for our boilers are brown coal briquettes with a calorific value of 19 – 23 MJ.kg-1. Brown coal briquettes have low ash content and a long burning time.






Quality wood briquettes with a diameter of 80 – 130 mm, a length of 200 – 380 mm and a calorific value of 16 – 19 MJ.kg-1.

Ecological wood briquettes are produced from wood waste by high-pressure pressing without any chemical binders. They are manufactured and sold by a number of companies in the Czech Republic. However, the quality of wood briquettes varies. We recognize high-quality wood briquettes by the fact that they do not break down into sawdust during combustion in the application space. Wood briquettes, which break down into sawdust, can only be burned in combination with lump wood or brown coal, but never separately. They block the gasification nozzle or the gasification grate.




Quality wood pellets with a diameter of 6 – 8 mm, a length of 5 to 25 mm and a calorific value of 16 – 19 MJ.kg-1 (white pellets).

Pellets are a new fuel produced in a similar way as wood briquettes from waste wood, by pressing. We consider white pellets made of soft wood without bark to be quality pellets. Pellets with a diameter of 6 to 8 mm are used for Atmos boilers.
Other pellets from rapeseed or cereal straw are currently only a marginal and very problematic issue, so our company does not deal with their combustion.