ATTACK 35 DPX STANDARD - wood gasification boiler

Product detailed description

ATTACK 35 DPX STANDARD – wood gasification boiler with an output of 35 kW

ATTACK 35 DPX STANDARD is a modern gasification (pyrolysis) wood boiler with a nominal output of 35 kW, designed for heating family houses, cottages, commercial premises 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, which allows it to achieve 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 common family houses and smaller premises, where emphasis is placed on a balanced price, easy operation and the reliability of a proven cast-iron and steel construction.

The 35 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 (pyrolyzed) in the upper loading chamber under insufficient air supply, then the resulting combustible gas (a mixture of CO, H2 and hydrocarbons) together with the supplied secondary air is 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 substantially 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 insufficiently controlled air supply, producing a large amount of unburned combustion products (tar, soot, CO), which escape through the chimney and clog the flue pipe. The ATTACK 35 DPX STANDARD gasification boiler, on the other hand, splits combustion into two separate phases taking place in two chambers one above the other. In the upper loading chamber, the wood gasifies at high temperature and insufficient oxygen (it does not burn directly), while the resulting combustible wood gas is pushed by the combustion air fan through a ceramic (refractory) 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 lifespan of the flue pipe and chimney) and the possibility of smooth output regulation according to current heat demand, since the fan regulates the intensity of combustion instead of manually throttling the chimney.

Key features of the ATTACK 35 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 100 l allowing loading of a larger amount of wood 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 into the chimney, thereby increasing the boiler's efficiency.
• Mechanical cleaning of the heat exchanger using an external lever/handle – the operator simply removes ash and soot deposits from the heat exchange surfaces with a few movements of the lever without the need 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 combustion chamber lining made of high-quality refractory material resistant to the high temperatures generated by 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 design of the Standard series.
• Large service door for convenient access to the combustion chamber, nozzle and heat exchanger during cleaning and maintenance.
• Safety heat exchanger / possibility of connecting a cooling circuit against overheating of the boiler (we recommend adding a thermal safety valve in accordance with valid Slovak legislation).
• Readiness for conversion to automatic operation using the DPD30900 kit for burning pellets (COMBI Pellet), giving 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 the ATTACK 35 DPX STANDARD

Differences between the Standard and Profi series

The 35 DPX STANDARD boiler in the Standard design is controlled by a simpler electronic control of the combustion air fan, which ensures stable combustion and good efficiency at a lower purchase cost compared to the Profi series. This is a proven and undemanding solution suitable especially for smaller and medium-sized households, where full automation or weather-compensated control is not necessary. 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 a high temperature of flue gases in the combustion chamber and are therefore sensitive to so-called low-temperature corrosion, which occurs if heating water that is too cold (lower than 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 lifespan of the boiler body. Therefore, we always recommend installing a mixing (three-way) circuit with a thermostatic head in the heating system – for example ATTACK / Oventrop or ESBE LTC361 – which maintains the temperature of the return water to the boiler at a minimum of 60 °C until the boiler reaches operating temperature. This mixing circuit is also a condition for recognition of the extended warranty on the boiler body (see the Warranty chapter below).

Given 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's output and the heated area of the building). The buffer tank allows the loaded batch of wood to be burned all at once at optimal output and the heat to be "stored" for use, which is then gradually drawn into the heating circuit during the day. Without a buffer tank, the boiler's output is frequently throttled, which increases tar formation, reduces efficiency and shortens the lifespan of both the boiler and the flue pipe. Installation, connection to the flue pipe, connection to the electrical network and initial commissioning should always be carried out by an authorized heating technician/service technician in accordance with the project documentation, applicable legislation (especially the STN standards and regulations on boiler rooms) and the manufacturer's installation manual. Initial commissioning should be carried out by an authorized ATTACK service technician, which is also one of the conditions for claiming the warranty.

Fuel and its preparation

The recommended fuel for the ATTACK 35 DPX STANDARD boiler is dry firewood (preferably hard deciduous wood – beech, oak, hornbeam) with moisture content up to 20 %. The moisture content of the wood fundamentally affects both the output and the lifespan of the boiler – wet or freshly cut wood (moisture content of 40 % or more) significantly reduces heating value, causes incomplete gasification, increased formation of tar and soot, and can even lead to the fire going out. Therefore, store wood for at least 1–2 heating seasons under a shelter with good ventilation. The length of the logs should correspond to the dimensions of the boiler's loading chamber (usually up to approx. 50 cm), and the thickness of the logs should be approx. 8–15 cm for even and smooth gasification.

Possibility of conversion to automatic operation – COMBI Pellet

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

Maintenance and cleaning

Regular maintenance is key to maintaining the high efficiency and long lifespan of the ATTACK 35 DPX STANDARD boiler. We recommend emptying the ash pan and the space under the grate depending on the intensity of heating, usually several times a week. Mechanical cleaning of the heat exchanger using the external lever should be carried out according to the operating manual, ideally once a day during intensive seasonal operation – this will extend the interval between major service cleaning and maintain the declared efficiency of the boiler. 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 35 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 35 kW, so a buffer tank allows the batch of wood to be burned all at once under optimal conditions and the heat to be stored for later use. Without it, the output is throttled, resulting in increased tar formation and a shorter lifespan of the boiler.

What is the recommended moisture content of 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 fouling the heat exchanger and chimney.

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

Can the 35 DPX STANDARD boiler be converted to pellets later?
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 design, the Profi series offers more precise electronic control with a display, the possibility of weather-compensated control based on outdoor temperature, and usually thicker insulation of the boiler body, resulting in higher 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 should always be carried out by an authorized heating technician or an authorized ATTACK service technician, in accordance with the installation manual and applicable legislation. This is also a condition for the validity of the warranty.

What flue pipe diameter does the boiler require?
The ATTACK 35 DPX STANDARD boiler is standardly equipped with a chimney connection with a diameter of 180 mm; however, the exact chimney draught and diameter of the chimney must be assessed individually according to the height and type of chimney (we recommend consultation with a chimney sweep or designer).

Why choose the ATTACK 35 DPX STANDARD

The ATTACK brand 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 commonly available and service is not dependent on imports from abroad. The 35 DPX STANDARD boiler is designed to last decades of operation if the recommended conditions are met (protection against low-temperature corrosion, quality dry wood, regular maintenance). The combination of cast iron and steel components, ceramic lining of the combustion chamber and well-thought-out mechanical cleaning of the heat exchanger is among the proven solutions tested over the years in practice, which are appreciated by both installation companies and end customers in everyday operation.

When choosing the output of the 35 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 area of the house. An undersized boiler cannot cover the heat loss on the coldest days, while, on the other hand, a significantly oversized boiler works more often at partial output, which for solid fuel boilers reduces efficiency and increases tar formation. If in doubt about the correct choice of output, we recommend consulting a heating designer or directly a sales representative of ATTACK.

Emissions and environmentally friendly operation

Thanks to two-stage controlled combustion and a high operating temperature in the combustion chamber, the ATTACK 35 DPX STANDARD boiler achieves significantly lower emissions of particulate matter, 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) placed on solid fuel boilers placed on the EU market. Lower emissions also mean fewer deposits in the chimney and flue pipe, which reduces the risk of a soot fire in the chimney and extends the interval required between cleaning by a chimney sweep.

Warranty

For ATTACK DPX wood gasification boilers, the manufacturer provides a standard warranty of 36 months from the date of commissioning of the boiler, but no more than 42 months from the date of dispatch of the boiler 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 warranty of 7 years on the boiler body can be claimed. For the warranty to be valid, the initial commissioning must be carried out by an authorized ATTACK service technician and the prescribed method of operation must be followed (especially fuel moisture content and protection against low-temperature corrosion). Exact warranty conditions can be found in the warranty certificate supplied with the boiler.