ATTACK 20 PLQ COMBI - stationary cast iron gas 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 shocks, and 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 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 gets damaged, only the affected section needs to be replaced instead of the entire 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 rather than 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 PLQ 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 range from ATTACK, this means that the boiler itself does not have its own (built-in) domestic hot water (DHW) preparation. Therefore, to heat domestic hot water, the boiler 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 is required for hot water draw-off at several points simultaneously, since storage water heaters can better cover even a temporarily higher DHW demand than instantaneous heating.

The ATTACK PLQ COMBI range is positioned a notch above the basic EKO COMBI range. Compared to it, it offers somewhat more comfortable operation and generally also a wider output modulation range (the boiler can operate within the range stated in the product name, not just at a single fixed value), which in practice results in smoother adaptation of output to the current heat loss of the building and somewhat more economical operation during transitional seasons (spring, autumn). PLQ COMBI is a suitable choice for customers who want a slight upgrade compared to the most basic range, while still staying at a reasonable price level.

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 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 (long-term low return water temperature), can gradually damage thin-walled steel exchangers.

Another practical argument is the already mentioned sectional (segmented) construction. The cast-iron exchanger is not made of a single piece, but of several sections stacked on top of each other and connected by sealing gaskets. If, over the years of operation, one section were to be damaged (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 usually 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 figure in the technical parameters table below) and a somewhat slower thermal response when starting from a cold state - however, for a stationary boiler intended for long-term, predominantly continuous operation (not frequent on/off cycling as in a holiday cottage used a few times a year), these are rather marginal drawbacks compared to the benefit of a long service life and easier reparability.

Who is this boiler suitable for

The ATTACK PLQ 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 designed to be wall-mounted 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 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 valued
• Smaller facilities, workshops, guesthouses, or cottages with year-round or near year-round operation, where investing in a higher-quality body pays off through 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-hung solution for an apartment or a smaller housing 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-hung condensing boiler range.

Key features

• Stationary (floor-standing) design with a cast-iron heat exchanger - high resistance to corrosion and thermal shocks
• Nominal heat output of 14.5-18 kW, fuel: natural gas (LPG version available on request/depending on 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 - if damaged, 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
• Wider output modulation range within the stated kW range - smoother adaptation to the building's heat loss
• The delivery includes the boiler body itself, including the burner and basic control - external DHW storage 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 stated as an approximate estimate 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 recess 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 offering includes the so-called Z-series of storage tanks (e.g. Z100PLUS, Z125PLUS, Z100NTR, Z125NTRA, Z160NTRA, Z125OKC, Z160OKC, Z200OKC, and other versions including wall-hung horizontal 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 range (up to approx. 18 kW), a smaller storage tank volume from the ATTACK Z-series is generally sufficient, e.g. ATTACK Z 100 PLUS OKH NTR/HV, Z 100 OKC/NTR/HV, or the wall-hung version Z 125 OKC - the choice between a 100 vs. 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.

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 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 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 (piping route, placement of pumps, safety and mixing valves) depends on the specific boiler room layout 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 will be happy to help you choose the right combination of boiler output and storage tank volume based on the number of people in the household and the number of simultaneously used hot water draw-off points - do not hesitate to contact us before purchase if you are not sure about the correct choice.

Maintenance and service in practice

As with any gas appliance, with the ATTACK stationary cast-iron boiler it also holds true that a regular service inspection (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 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 the flue gas path, and verifying correct combustion settings.

Compared to modern condensing boilers, maintaining an atmospheric cast-iron boiler is usually 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, keep in mind that atmospheric cast-iron boilers of this construction 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 any cost is a decisive criterion for you, we will be happy to discuss alternatives from the ATTACK condensing range as well.

Frequently asked questions

1. Is domestic hot water (DHW) heating included in the price of this boiler?
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 range (up to approx. 18 kW), a smaller storage tank volume from the ATTACK Z-series is generally sufficient, e.g. ATTACK Z 100 PLUS OKH NTR/HV, Z 100 OKC/NTR/HV, or the wall-hung version Z 125 OKC - the choice between a 100 vs. 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 PLQ COMBI range differ from the other ranges of the ATTACK COMBI cast-iron offering (EKO, PLQ, KLQ, E, EZ)?
In short: compared to the basic EKO COMBI range, it generally offers a wider output modulation range within the stated kW range, which can result in smoother adaptation of output to the current heat demand.

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/depending on 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 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. The cast-iron exchanger body is covered by an extended 5-year warranty. The exact warranty conditions are governed by the warranty card 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 for connection to a naturally draught chimney. The suitability of a specific chimney (diameter, height, material) needs to be assessed individually, ideally during an on-site inspection 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 multiple 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 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, 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 utilise the condensation of water vapour from the flue gases 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 will be happy to help you weigh 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 also recommend 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 have any doubts when choosing the combination of boiler + storage tank + accessories, do not hesitate to contact us before ordering - we will be happy to 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 PLQ 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 ends 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 specified by the manufacturer must be observed (usually by a qualified service technician authorised for this activity), and a proper service booklet/warranty card must be kept. If you have any questions about the warranty, service, or choosing suitable accessories (DHW storage tank, circulation pump, chimney parts, control), do not hesitate to contact us - we will be happy to help you choose and order a complete solution tailored to your needs.