ATTACK 25 DPX STANDARD - wood gasification boiler

Product detailed description

ATTACK 25 DPX STANDARD – wood gasification boiler with an output of 25 kW

ATTACK 25 DPX STANDARD is a modern gasification (pyrolysis) wood boiler with a nominal output of 25 kW, designed for heating family houses, cottages, businesses and smaller industrial buildings where quality firewood is available. The DPX Standard series boiler combines the proven cast iron and steel construction of the ATTACK brand with controlled two-stage combustion technology, thanks to which it achieves significantly higher efficiency and lower emissions than classic wood boilers with bottom or top burning. The ATTACK DPX series is a compact gasification boiler designed for ordinary family houses and smaller businesses, where emphasis is placed on a balanced price, ease of use and the reliability of a proven cast iron and steel construction.

The 25 DPX STANDARD boiler belongs to energy class A+ and meets the current emission requirements (Ecodesign) placed on solid fuel boilers in the European Union. Due to the gasification principle, the firewood in the boiler is not burned all at once, but gradually – first it is gasified (pyrolysed) in the upper loading chamber under insufficient air supply, and the resulting combustible gas (a mixture of CO, H2 and hydrocarbons), together with supplied secondary air, is then perfectly burned in the ceramic combustion nozzle and lower combustion chamber at temperatures exceeding 900 °C. The result is a longer burning time per load of wood, higher efficiency (typically above 88 %) and considerably lower wood consumption per kilowatt-hour of heat produced compared to a classic boiler.

How wood gasification works and why it is more efficient

A common wood boiler with bottom burning burns fuel all at once with an insufficiently controlled air supply, producing large amounts of unburned combustion products (tar, soot, CO) that escape through the chimney and clog the flue pipe. The ATTACK 25 DPX STANDARD gasification boiler, on the other hand, divides combustion into two separate phases taking place in two chambers, one above the other. In the upper loading chamber, wood gasifies at high temperature and with insufficient oxygen (it is not directly burned there), while the resulting combustible wood gas is pushed by the combustion air fan through a ceramic (firebrick) nozzle into the lower combustion chamber. There, the gas mixes with secondary air and burns perfectly at a very high temperature. This process brings three main benefits: significantly higher combustion efficiency, minimal formation of tar and soot (less cleaning, longer service life of the flue pipe and chimney) and the possibility of smoothly regulating output according to current heat demand, since the fan regulates the intensity of combustion instead of manually throttling the chimney.

Key features of the ATTACK 25 DPX STANDARD boiler

• Wood gasification combustion with two-stage combustion and high efficiency above 88 %, energy class A+.
• Large loading space with a volume of approximately 80 l, allowing a larger amount of wood to be loaded and a longer interval between refuelling.
• Turbulators in the heat exchanger – rotating turbulators increase the turbulence of flue gases in the heat exchange area, improve heat transfer to the heating water and reduce the temperature of flue gases leaving the chimney, thereby increasing boiler efficiency.
• Mechanical cleaning of the heat exchanger using an external lever/handle – the operator simply uses a few movements of the lever to remove ash and soot deposits from the heat exchange surfaces without having to disassemble the boiler.
• Robust cast iron/steel construction of the boiler body with increased wall thickness resistant to operational wear and thermal stress.
• Ceramic combustion nozzle and lining of the combustion chamber made of quality firebrick resistant to the high temperatures generated when burning wood gas.
• Combustion air fan with output control ensuring the optimal air-to-fuel ratio at different boiler loads.
• Electronic fan control ensuring stable combustion in the simpler Standard series design.
• Large service door for comfortable access to the combustion chamber, nozzle and heat exchanger during cleaning and maintenance.
• Safety heat exchanger / option to connect a cooling circuit against boiler overheating (we recommend adding a thermal safety valve in accordance with current Slovak legislation).
• Ready for conversion to automatic operation using the DPD30900 kit for burning pellets (COMBI Pellet), which gives the boiler the option of fully automatic refuelling.
• Low emissions and compliance with Ecodesign requirements for solid fuel boilers applicable in the EU.

Technical parameters of ATTACK 25 DPX STANDARD

Differences between the Standard and Profi series

The 25 DPX STANDARD boiler in the Standard version is controlled by a simpler electronic regulation of the combustion air fan, which ensures stable combustion and good efficiency at a lower purchase cost compared to the Profi series. It is a proven and undemanding solution suitable especially for smaller and medium-sized households, where full automation or weather-compensated control is not required. If you later require more precise output control based on outdoor temperature, we recommend considering the related DPX Profi model of the same output.

Installation and commissioning

ATTACK DPX gasification boilers operate with high flue gas temperature in the combustion chamber and are therefore sensitive to so-called low-temperature corrosion, which occurs if heating water that is too cold (below approx. 60 °C) returns to the boiler. During long-term operation with a low return temperature, acidic combustion products condense on the walls of the heat exchanger, which significantly shortens the service life of the boiler body. We therefore always recommend fitting the heating system with a mixing (three-way) circuit with a thermostatic head – for example ATTACK / Oventrop or ESBE LTC361 – which keeps the temperature of the water returning to the boiler at a minimum of 60 °C until the boiler heats up to operating temperature. This mixing circuit is also a condition for recognising the extended warranty on the boiler body (see the Warranty chapter below).

Due to the nature of gasification combustion (the boiler works best at an output close to nominal), we strongly recommend supplementing the heating system with a buffer tank (e.g. the ATTACK AK or AS series with a suitable volume according to the boiler output and the heated area). A buffer tank allows the loaded batch of wood to be burned all at once at optimal output, and the heat to be "stored" for later use, being gradually drawn off into the heating circuit throughout the day. Without a buffer tank, the boiler output is frequently throttled, which increases tar formation, reduces efficiency and shortens the service life of both the boiler and the flue pipe. Always have the installation, connection to the flue pipe, connection to the electrical network and initial commissioning carried out by an authorised heating engineer/service technician in accordance with the project documentation, applicable legislation (especially STN standards and boiler room regulations) and the manufacturer's installation manual. Initial commissioning should be carried out by an authorised ATTACK service technician, which is also one of the conditions for claiming the warranty.

Fuel and its preparation

The recommended fuel for the ATTACK 25 DPX STANDARD boiler is dry firewood (preferably hard deciduous wood – beech, oak, hornbeam) with a moisture content of up to 20 %. The moisture content of the wood significantly affects both the output and the service life of the boiler – wet or freshly cut wood (moisture content of 40 % or more) considerably reduces the heating value, causes incomplete gasification, increased tar and soot formation and can even lead to the fire going out. Therefore, store wood for at least 1–2 heating seasons under a well-ventilated shelter. The length of the logs should correspond to the dimensions of the boiler's loading chamber (usually up to approx. 50 cm), with a log thickness of approx. 8–15 cm for even and smooth gasification.

Option of conversion to automatic operation – COMBI Pellet

If you are considering, in the future, more convenient automatic operation without the need for daily wood refuelling, the ATTACK 25 DPX STANDARD boiler can be additionally converted to burn wood pellets using the DPD30900 kit with a 30 kW pellet burner. This conversion kit is designed for ATTACK 25-35 DPX Standard/Profi boilers and includes a burner, pellet hopper and the necessary control electronics, including connection to the boiler's existing controls. When ordering the conversion kit, the serial number of the specific boiler to which the kit will be fitted must be provided, so that the service technician can verify compatibility and prepare the correct components. After conversion, the boiler works as a fully automatic pellet heat source, while the original wood-burning function can, depending on the version, be retained as a backup (combined wood/pellet operation).

Maintenance and cleaning

Regular maintenance is key to maintaining the high efficiency and long service life of the ATTACK 25 DPX STANDARD boiler. We recommend emptying the ash pan and the space under the grate according to heating intensity, usually several times a week. Perform mechanical cleaning of the heat exchanger using the external lever according to the operating manual, ideally once a day during intensive seasonal operation – this will extend the interval between major service cleanings and maintain the boiler's declared efficiency. At least once a year (before the start of the heating season), we recommend having a comprehensive service inspection of the boiler carried out, including checking the door seal, the condition of the ceramic nozzle, the combustion chamber lining, and the functionality of the fan and controls.

Frequently asked questions

Is a buffer tank needed for the ATTACK 25 DPX STANDARD boiler?
It is not a legal requirement, but it is strongly recommended. The gasification boiler works most efficiently at an output close to the nominal 25 kW, so a buffer tank allows a batch of wood to be burned all at once under optimal conditions, storing the heat for later use. Without it, output throttling occurs, along with increased tar formation and a shorter boiler service life.

What is the recommended moisture content of the wood?
The recommended moisture content of firewood is up to 20 %, which usually corresponds to wood dried for at least 1–2 years under a shelter. Wetter wood reduces efficiency and increases the risk of clogging the heat exchanger and chimney.

What is low-temperature corrosion and how can it be avoided?
This is damage to the boiler body caused by the condensation of acidic combustion products at too low a return water temperature. It is solved by fitting a mixing (three-way) circuit, which keeps the temperature of the water returning to the boiler at a minimum of 60 °C.

Can the 25 DPX STANDARD boiler later be converted to pellets?
Yes, using the DPD30900 conversion kit designed for 25-35 DPX Standard/Profi boilers, which adds a pellet burner and the necessary control electronics for fully automatic operation.

What is the difference between the Standard and Profi series?
Compared to the Standard version, the Profi series offers more precise electronic control with a display, the option of weather-compensated control based on outdoor temperature, and usually thicker insulation of the boiler body, providing greater operating comfort and slightly lower fuel consumption during long-term operation.

Who is allowed to carry out the initial commissioning of the boiler?
Initial commissioning, connection to the flue pipe and electrical network must always be carried out by an authorised heating engineer or authorised ATTACK service technician, in accordance with the installation manual and applicable legislation. This is also a condition for the warranty to be valid.

What flue pipe diameter does the boiler require?
The ATTACK 25 DPX STANDARD boiler is standardly equipped with a chimney connection with a diameter of 150 mm; however, the exact chimney draught and diameter must be assessed individually according to the height and type of chimney (we recommend consulting a chimney sweep or designer).

Why choose the ATTACK 25 DPX STANDARD

ATTACK is a Slovak boiler manufacturer with a long tradition and an extensive service network throughout Slovakia, which is a great advantage when heating with solid fuel – spare parts (ceramic nozzles, seals, fans, control units) are readily available and service is not dependent on imports from abroad. The 25 DPX STANDARD boiler is designed to last for decades of operation provided the recommended conditions are met (protection against low-temperature corrosion, quality dry wood, regular maintenance). The combination of cast iron and steel components, ceramic combustion chamber lining and well thought-out mechanical cleaning of the heat exchanger is among the proven solutions, tested over the years in practice, appreciated by both installation companies and end customers in everyday operation.

When choosing the output of the 25 DPX STANDARD boiler, be guided primarily by the heat loss of the heated building calculated according to the applicable standard (STN EN 12831), not just approximately according to the floor area of the house. An undersized boiler will not be able to cover the heat loss on the coldest days, while a significantly oversized boiler works more often at partial output, which reduces efficiency and increases tar formation in solid fuel boilers. If in doubt about the correct choice of output, we recommend consulting a heating designer or directly an ATTACK sales representative.

Emissions and environmentally friendly operation

Thanks to two-stage controlled combustion and a high operating temperature in the combustion chamber, the ATTACK 25 DPX STANDARD boiler achieves significantly lower emissions of particulate pollutants, CO and organic compounds compared to classic wood boilers with bottom burning. The boiler meets the requirements of the Ecodesign regulation (Directive 2009/125/EC and related implementing regulations) for solid fuel boilers placed on the market in the EU. Lower emissions also mean fewer deposits in the chimney and flue pipe, which reduces the risk of a chimney soot fire and extends the interval needed between chimney sweep cleanings.

Warranty

The manufacturer provides a standard 36-month warranty for ATTACK DPX wood gasification boilers from the date the boiler is put into operation, but no more than 42 months from the date the boiler is shipped from the factory. If protection against low-temperature corrosion is installed (a mixing circuit maintaining a return temperature of at least 60 °C), an extended 7-year warranty on the boiler body can be claimed. For the warranty to be valid, initial commissioning must be carried out by an authorised ATTACK service technician and the prescribed method of operation must be observed (in particular fuel moisture content and protection against low-temperature corrosion). Exact warranty terms can be found in the warranty certificate supplied with the boiler.