ATTACK 15 EZ COMBI - stationary cast iron gas boiler 12-15 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 longest-proven heating solutions on the market. Cast iron as a heat exchanger material is highly resistant to corrosion and thermal shock, and it withstands a less gentle operating regime (frequent switching, fluctuations in return water temperature) better than thin-walled steel or aluminium heat exchangers. Thanks to this, cast-iron boilers have long enjoyed a reputation as robust and reliable devices suitable not only for standard family houses but also for larger buildings, facilities, workshops, small companies, or multi-generational houses with higher heat consumption.

Another advantage of the cast-iron body is easy maintenance and serviceability - a cast-iron heat exchanger usually consists of individual sections (segments), which means that if one of them gets damaged, only the affected section needs to be replaced instead of the whole heat exchanger. This can mean lower long-term service costs compared to one-piece heat exchangers. The stationary design (a boiler standing on the floor, not wall-mounted) 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 EZ COMBI range and is designed for a rated heat output of 12-15 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 domestic hot water, the boiler therefore needs to be supplemented with an external indirectly heated DHW storage tank (e.g. from the ATTACK Z-series - see the "How to connect" section below). This type of solution (boiler + separate storage tank) is common and proven especially where greater comfort of hot water draw-off at multiple points at the same time is required, since storage-type water heaters can cover even occasionally higher DHW demand better than instantaneous heating.

The ATTACK EZ COMBI range is the top of the cast-iron range of ATTACK COMBI stationary gas boilers. Accordingly, out of the five ranges (EKO, PLQ, KLQ, E, EZ) it also has the highest purchase price - this should correspond to better equipment, higher efficiency and/or lower operating noise compared to the lower ranges. We do not have the exact technical parameters that distinguish EZ COMBI from the E COMBI range (e.g. how many percent higher the efficiency is, how many decibels quieter the operation is) available as verified figures in our source data, so we deliberately do not state them - we do not want to provide made-up values. If an exact comparison is important to you, we recommend contacting our support team or the ATTACK manufacturer directly before deciding - we will be happy to help you find the current technical data sheet.

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

When choosing a stationary gas boiler, customers often ask why they should choose a cast-iron heat exchanger when cheaper steel or lighter aluminium solutions are also available on the market. The answer is primarily related to the long-term durability of the material. Cast iron has a higher thermal inertia than thin-walled steel, which in practice means calmer, less "nervous" combustion 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 can gradually damage thin-walled steel heat exchangers under an unsuitable operating regime (long-term low return water temperature).

Another practical argument is the already mentioned sectional (segmented) construction. A cast-iron heat exchanger does not consist of a single piece, but of several sections stacked on top of each other and joined with sealing gaskets. If one section were to get damaged during 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 heat exchangers, this option usually does not exist, and damage to the heat exchanger means replacing the entire boiler or at least the whole heat exchanger block.

The disadvantage of cast iron is its higher weight (see the approximate figure 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, mostly continuous operation (not frequent on/off switching as in a cottage used only a few times a year), these are rather marginal disadvantages compared to the benefit of a long service life and easier repairability.

Who this boiler is suitable for

The stationary cast-iron ATTACK EZ COMBI boiler with an output of 12-15 kW is a suitable choice especially where a boiler room is available (it is not intended for wall mounting like standard 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 a long service life and easy serviceability of the appliance 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 almost 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 line 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 residential unit, or a boiler with its own fast domestic hot water preparation without the need for a separate storage 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
• Rated heat output of 12-15 kW, fuel natural gas (LPG version on request/according to specific order specification)
• COMBI version = boiler without its own DHW preparation, designed to work with an external indirectly heated storage tank (e.g. ATTACK Z-series)
• Sectional (segmented) cast-iron heat exchanger - in case of damage allows replacement of a single section instead of the entire body
• Connection to a naturally draught chimney (atmospheric combustion)
• Robust construction suitable also for larger buildings and facilities with higher heating output requirements
• The highest standard within the ATTACK COMBI cast-iron range - the higher price corresponds to better equipment/efficiency/noise level (exact figures we recommend verifying with our sales team)
• The delivery includes the boiler body itself, including the burner and basic control - the external DHW storage tank, circulation pump, expansion vessel, chimney accessories and room thermostat are not included in the basic price unless explicitly stated

Technical parameters

Note: dimensions and weight are given as approximate estimates based on the output category and the usual 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 exact construction preparation of a room or niche for the boiler.

How to connect: boiler + external DHW storage 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) indirectly heated DHW storage tank. For this purpose, the ATTACK range offers the so-called Z-series of storage tanks (e.g. Z100PLUS, Z125PLUS, Z100NTR, Z125NTRA, Z160NTRA, Z125OKC, Z160OKC, Z200OKC, and other versions including horizontal wall-mounted OKCV variants) - we sell these storage tanks as a separate product, they are not included in the boiler's delivery or price.

For this power level (up to approx. 18 kW), a smaller storage tank volume from the ATTACK Z-series range is usually 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 at the same time.

The connection principle is briefly as follows: the boiler heats the heating (heat-transfer) water, which circulates both to the heating system (radiators, underfloor heating) and through the heat exchanger (coil) in the DHW storage tank, where it transfers heat to the domestic water. Switching between the heating circuit and the storage 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 electronics or by a separate room thermostat/controller. The exact connection (pipe routing, 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 authorized heating/gas professional who will also take into account the locally applicable standards and regulations for connecting a gas appliance.

When ordering the boiler and the storage tank, we will be happy to help you choose the right combination of boiler output and storage tank volume according to the number of people in the household and the number of simultaneously used hot water draw-off points - 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 (usually once a year, carried out by an authorized 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 heat exchanger and burner of soot and dust, checking the tightness of the joints between individual sections, checking the chimney draught and the flue gas path, and verifying correct combustion settings.

Compared to modern condensing boilers, maintenance of an atmospheric cast-iron boiler is usually simpler and cheaper - for example, there is no need to take care of a condensate trap or a heat 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 reach 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 be happy to discuss alternatives from the ATTACK condensing range with you as well.

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 heats only the heating water. To heat domestic hot water, an external indirectly heated storage tank (e.g. from the ATTACK Z-series) must be added, which is ordered and paid for separately.

2. Which DHW storage tank is suitable for a boiler with an output of 12-15 kW?
For this power level (up to approx. 18 kW), a smaller storage tank volume from the ATTACK Z-series range is usually 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 at the same time.

3. How does the EZ COMBI range differ from the other ranges of the ATTACK COMBI cast-iron lineup (EKO, PLQ, KLQ, E, EZ)?
In short: EZ COMBI is the top range in this ATTACK cast-iron line - the higher price should correspond to better equipment, higher efficiency, or quieter operation compared to the lower ranges, however, we recommend verifying the exact numerical comparison with us or directly with the manufacturer, as we do not have the exact figures available as verified data.

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

5. What is the warranty for 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 heat 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 carried out by a professional service technician).

6. Can the boiler be connected to an existing naturally draught chimney?
Yes, this is an atmospheric boiler intended for connection 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 masonry chimney.

7. Can the boiler be connected to a system with multiple heating circuits (e.g. radiators + underfloor heating)?
Yes, combining multiple circuits with different heating water temperatures is common - however, it 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 design engineer or directly with our team.

8. Can the boiler be ordered without a DHW storage tank, just the body itself?
Yes - this product represents the boiler body itself. The DHW storage 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 be happy to 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 the condensation of water vapour from the flue gas for additional heat gain, so its efficiency does not reach the values of modern condensing boilers. In return, it offers a simpler construction, lower sensitivity to the temperature of the return heating water, and usually 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 be happy to 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 storage tank 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 + storage tank + accessories, please do not hesitate to contact us before ordering - we will be happy to advise you so that you do not order something you will not ultimately need, or conversely, so that nothing essential is missing.

Warranty and service

ATTACK EZ 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 occurs first). The manufacturer provides an extended 5-year warranty on the cast-iron heat exchanger body itself. To claim the full warranty period, the commissioning conditions set by the manufacturer must be observed (usually by a professional service technician authorized 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 storage tank, circulation pump, chimney parts, controls), please do not hesitate to contact us - we will be happy to help you choose and order a complete solution tailored to your needs.