ATTACK 20 E COMBI - stationary gas cast iron boiler 14.5-18 kW

Product detailed description

ATTACK COMBI - stationary cast iron gas boiler

Stationary gas boilers with a cast iron heat exchanger are among the most durable and longest proven heating solutions on the market. Cast iron as an exchanger material is highly resistant to corrosion and thermal shock and tolerates less gentle operation (frequent switching, fluctuations in return water temperature) better than thin-walled steel or aluminium exchangers. Thanks to this, cast iron boilers have long enjoyed a reputation as robust and reliable devices suitable not only for ordinary family houses, but also for larger buildings, facilities, workshops, small businesses or multi-generational houses with higher heat consumption.

Another advantage of the cast iron body is easy maintenance and serviceability - a cast iron exchanger usually consists of individual sections (segments), which means that if one of them is damaged, only the affected section can be replaced instead of the whole exchanger. In the long run, this can mean lower servicing costs compared to one-piece exchangers. The stationary design (a boiler standing on the floor, not mounted on a wall) also simplifies installation at higher outputs and makes it easier to connect to a naturally draught chimney, which is commonly used in both older and newer boiler rooms.

The model you are currently viewing belongs to the ATTACK E COMBI range and is designed for a nominal heat output of 14.5-18 kW. It is a stationary gas boiler in the COMBI version - in the context of this cast iron ATTACK range, this means that the boiler itself does not have its own (built-in) domestic hot water (DHW) preparation. To heat hot water, the boiler therefore needs to be supplemented with an external indirect DHW tank (e.g. from the ATTACK Z-series range - see the "How to connect" section below). This type of solution (boiler + separate tank) is common and proven especially where there is a requirement for greater comfort of hot water draw-off at several points of use simultaneously, as tank heaters can cover even temporarily higher DHW consumption better than instantaneous heating.

The ATTACK E COMBI range follows on from the KLQ COMBI and represents an even higher equipment class within the ATTACK cast iron range. E COMBI boilers are intended for customers who, in addition to functional reliability, also require greater operating comfort. The exact technical differences compared to the KLQ COMBI range (e.g. the specific burner type, control details) are not available in full detail in our source data - if you need to know exactly how E COMBI differs from KLQ COMBI for your specific output level, we will gladly verify this before purchase and help you choose based on the manufacturer's current technical documentation.

Why a cast iron exchanger and not a steel or aluminium one?

When choosing a stationary gas boiler, customers often ask why they should opt for a cast iron exchanger when cheaper steel or lighter aluminium solutions are also available on the market. The answer is mainly related to the long-term durability of the material. Cast iron has higher thermal inertia than thin-walled steel, which in practice means calmer, less "nervous" combustion and less material stress during sudden changes in return water temperature (for example, when starting up a cold system after a longer shutdown). At the same time, cast iron is naturally more resistant to condensation corrosion, which, under an unsuitable operating regime (long-term low return water temperature), can gradually damage thin-walled steel exchangers.

Another practical argument is the already mentioned sectional (segmented) construction. A cast iron exchanger does not consist of a single piece, but of several sections stacked on top of each other and joined with sealing gaskets. If a single section were to become damaged over the years of operation (which is unlikely even with cast iron, but theoretically possible, for example due to mechanical damage or extreme neglect of maintenance), a service technician can replace only the affected section without having to replace the entire boiler body. With one-piece steel or aluminium exchangers, this option generally does not exist, and damage to the exchanger means replacing the entire boiler or at least the entire exchanger block.

The disadvantage of cast iron is its higher weight (see the indicative figure in the technical parameters table below) and a somewhat slower thermal response when starting up from cold - however, for a stationary boiler intended for long-term, mostly continuous operation (not frequent switching on/off as in a cottage used a few times a year), these are rather minor drawbacks compared to the benefit of a long service life and easier repairability.

Who is this boiler suitable for

The ATTACK E COMBI stationary cast iron boiler with an output of 14.5-18 kW is a suitable choice especially where a boiler room is available (it is not intended for wall mounting like common wall-hung combi boilers) and where a naturally draught chimney is available or planned. Typically, this includes:

• Family houses with their own boiler room or utility room, where long service life and easy serviceability of the device matter
• Larger buildings and multi-generational houses with higher heat consumption, where the robustness of the cast iron body is appreciated
• Smaller facilities, workshops, guesthouses or cottages with year-round or nearly year-round operation, where the investment in a higher-quality body pays off through a longer service life
• Renovations where an older cast iron boiler is being replaced and an existing chimney and gas supply sized for the given output are available

On the other hand, if you are looking for a compact wall-mounted solution for an apartment or a smaller apartment core, or a boiler with its own fast hot water preparation without having to deal with a separate tank, a cast iron stationary COMBI boiler is probably not the most suitable choice - in that case, we recommend consulting with us about a more suitable alternative from the ATTACK wall-mounted condensing boilers.

Key features

• Stationary (floor-standing) design with a cast iron heat exchanger - high resistance to corrosion and thermal shock
• Nominal heat output 14.5-18 kW, fuel: natural gas (LPG version available on request/according to the specific order specification)
• COMBI version = boiler without its own DHW preparation, designed to work with an external indirect tank (e.g. ATTACK Z-series)
• Sectional (segmented) cast iron exchanger - if damaged, allows replacement of a single section instead of the entire body
• Connection to a naturally draught chimney (atmospheric combustion)
• Robust construction suitable even for larger buildings and facilities with higher heating output requirements
• Increased operating comfort within the ATTACK cast iron range
• The delivery includes the boiler body itself, including the burner and basic controls - external DHW tank, circulation pump, expansion vessel, chimney accessories and room thermostat are not included in the base price unless explicitly stated

Technical parameters

Note: dimensions and weight are given as an indicative estimate based on the output category and typical construction of cast iron sectional boilers of this class - we recommend verifying the exact value for a specific unit in the manufacturer's current technical data sheet or directly with us before ordering, especially if you are planning precise construction preparation of a room or niche for the boiler.

How to connect: boiler + external DHW tank

Since this is a COMBI version without its own domestic hot water preparation, this boiler needs to be connected together with a separate (external) indirect DHW tank. In the ATTACK range, the so-called Z-series of tanks is used for this purpose (e.g. Z100PLUS, Z125PLUS, Z100NTR, Z125NTRA, Z160NTRA, Z125OKC, Z160OKC, Z200OKC and other versions including wall-mounted horizontal OKCV variants) - we sell these tanks as a separate product, they are not included in the boiler's delivery or price.

For this output level (up to approx. 18 kW), a smaller tank volume from the ATTACK Z-series range is generally sufficient, e.g. ATTACK Z 100 PLUS OKH NTR/HV, Z 100 OKC/NTR/HV or the wall-mounted version Z 125 OKC - the choice between 100 and 125 l volume depends mainly on the number of people in the household and how many hot water draw-off points (bathroom, kitchen, etc.) will be used simultaneously.

In brief, the connection principle is as follows: the boiler heats the heating (heat-carrying) water, which circulates both to the heating system (radiators, underfloor heating) and through a coil (heat exchanger) in the DHW tank, where it transfers heat to the domestic water. Switching between the heating circuit and tank heating is usually handled by a three-way valve (in the ATTACK range, e.g. models OT02 or OT44), controlled either by the boiler's electronics or by a separate room thermostat/controller. The exact connection (piping route, pump placement, safety and mixing fittings) depends on the specific layout of the boiler room and on whether it is a simple two-pipe system or a more complex system with multiple heating circuits - we recommend having the final connection designed and carried out by an authorised heating/gas specialist who will also take into account locally applicable standards and regulations for connecting a gas appliance.

When ordering the boiler and tank, we will gladly help you choose a suitable combination of boiler output and tank volume according to the number of people in the household and the number of hot water draw-off points used simultaneously - please do not hesitate to contact us before purchasing if you are not sure about the right choice.

Maintenance and service in practice

As with any gas appliance, with the ATTACK stationary cast iron boiler, regular service inspection (usually once a year, performed by an authorised service technician) is not only a condition for maintaining the warranty, but above all a prerequisite for safe and economical operation. For cast iron boilers, servicing usually includes checking and, if necessary, cleaning the exchanger and burner of soot and dust, checking the tightness of joints between individual sections, checking the chimney draught and flue gas path, and verifying correct combustion settings.

Compared to modern condensing boilers, maintaining an atmospheric cast iron boiler is generally simpler and cheaper - for example, there is no need to look after a condensate siphon or an exchanger sensitive to low return water temperature. On the other hand, it should be taken into account that atmospheric cast iron boilers of this design do not achieve the efficiency of the most modern condensing solutions, which is a common and fair trade-off between higher initial robustness/simplicity and the highest possible energy efficiency. If the lowest possible gas consumption at any cost is the decisive criterion for you, we will gladly discuss alternatives from the ATTACK condensing range with you.

Frequently asked questions

1. Does the price of this boiler include domestic hot water (DHW) heating?
No. This is a COMBI version without its own DHW preparation - the boiler only heats the heating water. To heat domestic hot water, an external indirect tank needs to be added (e.g. from the ATTACK Z-series range), which is ordered and paid for separately.

2. Which DHW tank is suitable for a boiler with an output of 14.5-18 kW?
For this output level (up to approx. 18 kW), a smaller tank volume from the ATTACK Z-series range is generally sufficient, e.g. ATTACK Z 100 PLUS OKH NTR/HV, Z 100 OKC/NTR/HV or the wall-mounted version Z 125 OKC - the choice between 100 and 125 l volume depends mainly on the number of people in the household and how many hot water draw-off points (bathroom, kitchen, etc.) will be used simultaneously.

3. How does the E COMBI range differ from other ranges in the ATTACK COMBI cast iron offer (EKO, PLQ, KLQ, E, EZ)?
In short: the E COMBI range is positioned above the KLQ COMBI in the ATTACK range, with increased operating comfort. We will gladly verify and clarify the exact technical differences compared to KLQ COMBI at this output on request.

4. What fuel type is the boiler designed for, and can it be converted to another fuel?
In its basic version, the boiler is designed for natural gas. An LPG (propane-butane) version is available on request/according to the specific order specification - we recommend stating this requirement when ordering or inquiring with our sales team in advance.

5. What is the warranty on this boiler?
ATTACK stationary gas boilers carry a warranty of 30 months from commissioning, but no more than 36 months from the date of dispatch from the manufacturer's warehouse. An extended 5-year warranty applies to the cast iron exchanger body. The exact warranty conditions are governed by the warranty certificate attached to the specific unit, and the prescribed commissioning conditions must be observed (usually by a qualified service technician).

6. Can the boiler be connected to an existing naturally draught chimney?
Yes, this is an atmospheric boiler designed to be connected to a naturally draught chimney. The suitability of a specific chimney (diameter, height, material) needs to be assessed individually, ideally during a site visit or in cooperation with a chimney sweep/inspection technician, especially if the boiler is being connected to an older brick chimney.

7. Can the boiler be connected to a system with multiple heating circuits (e.g. radiators + underfloor heating)?
Yes, combining several circuits with different heating water temperatures is common - however, this requires adding a mixing circuit with its own pump and control (in the ATTACK range, e.g. sets DPP25007/DPP25008 or ESBE versions DPP25020-DPP25022). We recommend discussing the connection design with a heating engineer or directly with our team.

8. Can the boiler be ordered without a DHW tank, just the body itself?
Yes - this product represents the boiler body itself. The DHW tank, circulation pump, chimney accessories, three-way valve and room thermostat/controller are ordered as separate items according to the needs of the specific installation - we will gladly prepare a complete list of the accessories needed, tailored to your project.

9. What is the difference between this atmospheric cast iron boiler and a modern condensing boiler?
An atmospheric cast iron boiler operates with a higher flue gas temperature and does not use condensation of water vapour from the flue gases to gain additional heat, so its efficiency does not reach the values of modern condensing boilers. In exchange, it offers a simpler construction, lower sensitivity to return heating water temperature, and generally simpler, cheaper maintenance without the need to deal with condensate drainage. The choice between a cast iron atmospheric and a condensing solution is always a trade-off between initial robustness/simplicity and the highest achievable efficiency - we will gladly help you weigh both directions according to your priorities.

10. Where can I order the boiler and how is delivery carried out?
You can order the boiler directly through the atria.sk online shop. When ordering, we recommend also considering ordering a suitable DHW tank from the Z-series and any additional accessories (chimney parts, three-way valve, circulation pump, room thermostat) so that you have a complete solution ready for installation. If you are unsure about the right combination of boiler + tank + accessories, please do not hesitate to contact us before ordering - we will gladly advise you so that you don't order something you won't ultimately need, or, conversely, so that nothing essential is missing.

Warranty and service

ATTACK E COMBI stationary cast iron gas boilers are covered by a standard warranty of 30 months from commissioning of the boiler, but no more than 36 months from the date of dispatch from the manufacturer's warehouse (whichever period occurs first). The manufacturer provides an extended 5-year warranty on the cast iron exchanger body itself. To claim the full warranty period, the commissioning conditions set by the manufacturer must be observed (usually by a qualified service technician authorised for this activity), and a proper service book/warranty certificate must be kept. If you have any questions about the warranty, service, or choosing suitable accessories (DHW tank, circulation pump, chimney parts, controls), please do not hesitate to contact us - we will gladly help you choose and order a complete solution tailored to your needs.