ATTACK 20 EZ 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 long-proven heating solutions on the market. Cast iron as an exchanger material is highly resistant to corrosion and thermal shock, and it withstands a less gentle operating regime (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 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 - the 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 floor-standing boiler, not wall-mounted) also simplifies installation at higher outputs and makes it easier to connect to a naturally-drafted flue, 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 rated for a nominal heat output of 14.5-18 kW. It is a stationary gas boiler in 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 higher comfort of hot water draw-off at several points at once is required, as storage tanks can cover even a temporarily 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, among 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 verified figures in our source data for the exact technical parameters by which EZ COMBI differs from the E COMBI range (e.g. by how many percent higher the efficiency is, or by how many decibels quieter the operation is), so we deliberately do not state them - we do not want to provide invented values. If an exact comparison is important to you, we recommend contacting our support team or the ATTACK manufacturer directly before deciding - we will gladly help you find the current technical data sheet.

Why a cast iron exchanger and not steel or aluminium?

When choosing a stationary gas boiler, customers often ask why they should choose 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 less stress on the material 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 can gradually damage thin-walled steel exchangers under an unsuitable operating regime (long-term low return water temperature).

Another practical argument is the already mentioned sectional (segmented) design. The cast iron exchanger is not made of a single piece but consists of several sections stacked on top of each other and joined with sealing gaskets. If one section were to be 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 whole boiler or at least the entire 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 cold - however, for a stationary boiler intended for long-term, predominantly 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 long service life and easier repairability.

Who this boiler is suitable for

The ATTACK EZ 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-drafted flue 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 appliance matter
• Larger buildings and multi-generational houses with higher heat consumption, where the robustness of the cast iron body is appreciated
• Smaller businesses, workshops, guesthouses or cottages with year-round or nearly year-round operation, where investing in a higher-quality body pays off over a longer service life
• Renovations where an older cast iron boiler is being replaced and an existing chimney and gas piping 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 to install a separate storage tank, a cast iron stationary 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-hung 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 specific order specification)
• COMBI version = boiler without its own DHW preparation, designed to work together with an external indirectly-heated storage tank (e.g. ATTACK Z-series)
• Sectional (segmented) cast iron exchanger - in case of damage, allows replacement of a single section instead of the whole body
• Connection to a naturally-drafted flue (atmospheric combustion)
• Robust construction also suitable 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 should be verified with our sales team)
• The delivery includes the boiler body itself including the burner and basic controls - the external DHW storage tank, circulation pump, expansion vessel, flue accessories and room thermostat are not included in the basic price unless explicitly stated

Technical parameters

Note: dimensions and weight are given as an approximate 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 exact construction preparation of the 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. ATTACK offers the so-called Z-series of storage tanks for this purpose (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 output level (up to approx. 18 kW), a smaller storage 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 a 100 vs. 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.

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 storage tank, where it transfers heat to the domestic water. Switching between the heating circuit and heating the storage tank is generally ensured by a three-way valve (ATTACK offers, for example, models OT02 or OT44), which is controlled either by the boiler electronics or 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 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 the storage tank, we are happy to help you choose a suitable combination of boiler output and storage tank volume according to the number of people in the household and the number of hot water draw-off points used simultaneously - 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 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 the exchanger and burner of soot and dust, checking the tightness of joints between individual sections, checking the flue draft and flue gas path, and verifying correct combustion settings.

Compared to modern condensing boilers, maintenance of an atmospheric cast iron boiler is generally simpler and cheaper - for example, there is no need to take care of a condensate siphon or an exchanger sensitive to low return water temperature. On the other hand, it should be noted 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 your decisive criterion is the lowest possible gas consumption at any cost, we are 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 only heats the heating water. To heat domestic hot water, an external indirectly-heated storage tank (e.g. from the ATTACK Z-series) needs to be added, which is ordered and paid for separately.

2. Which DHW storage 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 storage 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 a 100 vs. 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 EZ COMBI range differ from the other ranges of the ATTACK COMBI cast iron offer (EKO, PLQ, KLQ, E, EZ)?
In short: EZ COMBI is the top range in this ATTACK cast iron line - a 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 exact values available as verified data.

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 checking in advance with our sales team.

5. What is the warranty on 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 attached to the specific unit, and the prescribed commissioning conditions must be observed (generally by a professional service technician).

6. Can the boiler be connected to an existing naturally-drafted flue?
Yes, this is an atmospheric boiler designed to be connected to a naturally-drafted flue. The suitability of a specific flue (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, it requires adding a mixing circuit with its own pump and controls (ATTACK offers, for example, DPP25007/DPP25008 sets or ESBE versions DPP25020-DPP25022). We recommend discussing the connection design with a heating designer 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, flue accessories, three-way valve and room thermostat/controller are ordered as separate items according to the needs of the specific installation - we are 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 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 exchange, 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 are happy to help you consider 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 online shop. When ordering, we recommend also considering ordering a suitable DHW storage tank from the Z-series and any additional accessories (flue 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 choice of the boiler + storage tank + accessories combination, do not hesitate to contact us before ordering - we are happy to advise you so that you do not order something you will not end up needing, 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 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 warranty of 5 years on the cast iron exchanger body itself. To claim the full warranty period, the commissioning conditions specified by the manufacturer must be observed (generally by a professional 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 the choice of suitable accessories (DHW storage tank, circulation pump, flue parts, controls), do not hesitate to contact us - we are happy to help with the choice and with ordering a complete tailored solution.