ATTACK 15 EKO COMBI - stationary cast iron gas boiler 15 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 time-proven heating solutions on the market. Cast iron as an exchanger material is highly resistant to corrosion and thermal shock, and it withstands less gentle operating conditions (frequent switching, fluctuating 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 appliances suitable not only for typical family houses but also for larger buildings, facilities, workshops, small businesses, or multi-generational homes with higher heat demand.

Another advantage of a 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 needs to be replaced instead of the whole exchanger. In the long run, this can mean lower servicing costs compared to single-piece exchangers. The stationary design (a floor-standing boiler, not wall-mounted) also simplifies installation at higher outputs and makes it easier to connect to a chimney with natural draught, which is commonly used in both older and newer boiler rooms.

The model you are currently viewing belongs to the ATTACK EKO COMBI range and is rated for a nominal heat output of 15 kW. It is a stationary gas boiler in COMBI design - 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 domestic hot water, the boiler therefore needs to be supplemented with an external indirect DHW cylinder (e.g. from the ATTACK Z-series - see the "How to connect" section below). This type of solution (boiler + separate cylinder) is common and proven especially where greater comfort is required when drawing hot water at multiple points at the same time, since storage cylinders can cover even temporarily higher DHW demand better than instantaneous heating.

The ATTACK EKO COMBI range is the basic, entry-level line of ATTACK cast-iron stationary boilers. It is intended for customers looking for a simple, reliable and affordable heating solution for a family house or smaller facility without unnecessary extra features. EKO COMBI builds on the proven design of the cast-iron exchanger and basic automation, which makes it one of the most accessible stationary cast-iron gas boilers in the ATTACK range. It is a choice for those who expect above all functionality, long-term operational stability and low acquisition costs, and who are willing to trade more advanced comfort features for a lower price.

Why a cast-iron exchanger rather than steel or aluminium?

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 a calmer, less "nervous" combustion process and lower material stress during sudden changes in return water temperature (for example, when a cold system starts up after a longer shutdown). At the same time, cast iron is naturally more resistant to condensation corrosion, which, under an unsuitable operating regime (permanently low return water temperature), can gradually damage thin-walled steel exchangers.

Another practical argument is the already mentioned sectional (segmented) design. 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, over the years of operation, one section were to become damaged (which is unlikely even with cast iron, but theoretically possible, e.g. 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 single-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 approximate value in the technical parameters table below) and a somewhat slower thermal response when starting up from a cold state - however, for a stationary boiler intended for long-term, predominantly continuous operation (not frequent switching on/off as with a cottage used only a few times a year), these are rather marginal drawbacks compared to the benefit of a long service life and easier repairability.

Who is this boiler suitable for

The ATTACK EKO COMBI stationary cast-iron boiler with a 15 kW output is a suitable choice especially where a boiler room is available (it is not designed to be wall-mounted like common wall-hung combi boilers) and where a chimney with natural draught is available or planned. Typically, this includes:

• Family houses with their own boiler room or utility room, where a long service life and easy serviceability of the appliance matter
• Larger buildings and multi-generational homes with higher heat demand, 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 housing unit, or a boiler with its own fast DHW preparation without the need for a separate cylinder, a stationary cast-iron COMBI boiler is probably not the most suitable choice - in that case, we recommend consulting us about a more suitable alternative from the ATTACK wall-mounted condensing boiler range.

Key features

• Stationary (floor-standing) design with a cast-iron heat exchanger - high resistance to corrosion and thermal shock
• Nominal heat output 15 kW, fuel natural gas (LPG version available on request/according to the specific order specification)
• COMBI design = boiler without its own DHW preparation, intended for use with an external indirect cylinder (e.g. ATTACK Z-series)
• Sectional cast-iron exchanger - if damaged, allows replacement of a single section instead of the entire body
• Connection to a chimney with natural draught (atmospheric combustion)
• Robust construction suitable even for larger buildings and facilities with higher heating output requirements
• Basic, proven equipment without unnecessary extras - emphasis on simplicity and low acquisition cost
• The delivery includes the boiler body itself, including the burner and basic control - the external DHW cylinder, 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 approximate estimate based on the output category and typical design 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 cylinder

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 cylinder. For this purpose, the ATTACK range offers the so-called Z-series of cylinders (e.g. Z100PLUS, Z125PLUS, Z100NTR, Z125NTRA, Z160NTRA, Z125OKC, Z160OKC, Z200OKC and other versions including wall-mounted horizontal OKCV variants) - these cylinders are sold as a separate product and are not included in the delivery or price of the boiler.

For this output level (up to approx. 18 kW), a smaller cylinder volume is generally sufficient within the ATTACK Z-series range, 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 a 100 and 125 l volume mainly depends on the number of people in the household and how many hot water draw-off points (bathroom, kitchen, etc.) will be used simultaneously.

The connection principle is briefly as follows: the boiler heats the heating (heat transfer) water, which circulates both into the heating system (radiators, underfloor heating) and through the exchanger (coil) in the DHW cylinder, where it transfers heat to the domestic water. Switching between the heating circuit and cylinder heating is generally handled by a three-way valve (in the ATTACK range, e.g. the OT02 or OT44 models), controlled either by the boiler electronics or a separate room thermostat/controller. The exact connection (piping layout, placement of pumps, 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 implemented by an authorised heating/gas professional who will also take into account locally applicable standards and regulations for connecting a gas appliance.

When ordering the boiler and cylinder, we will gladly help you choose the right combination of boiler output and cylinder volume based on 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 servicing in practice

As with any gas appliance, a regular service inspection of the ATTACK stationary cast-iron boiler (generally once a year, carried out 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 generally includes checking and, if necessary, cleaning soot and dust from the exchanger and burner, checking the tightness of the joints between individual sections, checking the chimney draught and flue 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 all costs is a decisive criterion for you, we will also gladly discuss alternatives from the ATTACK condensing range.

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 cylinder needs to be added (e.g. from the ATTACK Z-series), which is ordered and paid for separately.

2. Which DHW cylinder is suitable for a boiler with 15 kW output?
For this output level (up to approx. 18 kW), a smaller cylinder volume is generally sufficient within the ATTACK Z-series range, 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 a 100 and 125 l volume mainly depends 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 EKO COMBI range differ from the other ranges in the ATTACK COMBI cast-iron line-up (EKO, PLQ, KLQ, E, EZ)?
In short: it is the basic, entry-level range in the ATTACK cast-iron boiler line-up - simpler equipment, lower acquisition price, suitable for customers who prioritise functionality and price over additional comfort.

4. What type of fuel 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 contacting our sales team in advance.

5. What warranty applies to this boiler?
ATTACK stationary gas boilers are covered by a 30-month warranty 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 terms are governed by the warranty certificate supplied with the specific unit, and the prescribed commissioning conditions must be observed (generally performed by a qualified service technician).

6. Can the boiler be connected to an existing chimney with natural draught?
Yes, this is an atmospheric boiler designed for connection to a chimney with natural draught. 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 masonry 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. the DPP25007/DPP25008 sets 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 cylinder, just the body itself?
Yes - this product represents the boiler body itself. The DHW cylinder, 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 accessories 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, which is why its efficiency does not reach the values of modern condensing boilers. In return, it offers a simpler construction, lower sensitivity to the 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 up both directions according to your priorities.

10. Where can I order the boiler and how does delivery work?
You can order the boiler directly through the atria.sk e-shop. When ordering, we recommend also considering a suitable DHW cylinder from the Z-series and any additional accessories (chimney parts, three-way valve, circulation pump, room thermostat) at the same time, so that you have a complete solution ready for installation. If you are unsure about the right combination of boiler + cylinder + accessories, please do not hesitate to contact us before ordering - we will gladly advise you so that you do not order something you will not eventually need, or, on the other hand, so that nothing essential is missing.

Warranty and service

ATTACK EKO COMBI stationary cast-iron gas boilers are covered by a standard warranty of 30 months from commissioning, but no more than 36 months from the date of dispatch from the manufacturer's warehouse (whichever period ends first). The manufacturer provides an extended 5-year warranty on the cast-iron exchanger body itself. To claim the full warranty period, the manufacturer's commissioning conditions must be met (generally 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, servicing, or choosing suitable accessories (DHW cylinder, circulation pump, chimney parts, controls), please do not hesitate to contact us - we will gladly help you choose and order a complete tailored solution.