ATTACK Atmospheric NSK 24 - gas atmospheric boiler (New)

Product detailed description

ATTACK Atmospheric NSK 24 is a new addition to the ATTACK portfolio and represents a return to a proven, simpler concept of a wall-mounted gas boiler without condensing technology. While condensing boilers of the KT/KST/KZT series offer higher efficiency, they generally require a plastic flue system (concentric or split) and condensate drainage into the sewer system. The atmospheric NSK 24 boiler, on the other hand, uses a classic chimney flue with natural draught, which in many renovations significantly simplifies and reduces the cost of installation.

Condensing vs. atmospheric boiler – an honest comparison

To help you make the right decision, here are the real differences between the two technologies without unnecessary embellishment:

• Efficiency: A condensing boiler can also utilize the heat contained in the water vapor of the flue gases (condensing heat), which is why it achieves higher seasonal efficiency (typically around 93%) and lower heating operating costs compared to an atmospheric boiler (efficiency approx. 91%, without utilizing condensing heat). Over time, the difference in gas consumption will show up in higher heating bills for the atmospheric boiler.
• Flue gas exhaust: The NSK 24 atmospheric boiler does not require a plastic concentric chimney or condensate drainage – a classic brick or steel chimney with natural draught (type B) is sufficient. This is a major advantage for renovations of flats in apartment buildings with a shared chimney shaft, or in older houses where installing a plastic flue system through the facade would be complicated, expensive, or structurally unsuitable.
• Installation costs: Thanks to the simpler flue system and the absence of condensate handling, installing the NSK 24 is generally cheaper and faster than installing a comparable condensing boiler, especially if the existing chimney can be used.
• Suitability: We recommend the atmospheric boiler mainly when replacing an old atmospheric boiler with a new one in the same configuration (renovation), where it is not economical or technically simple to build a new flue system. Conversely, we always recommend a condensing boiler for a completely new installation, or when a plastic flue system can be installed without major complications – in the long run it will save on operating costs.

Key features

• Output of 8 – 24 kW, suitable for a typical family house or flat.
• Uses a classic chimney flue (type B) with natural draught – no need for a plastic concentric chimney.
• Simpler design without a condensing heat exchanger and without condensate drainage.
• Electronic control with the option to connect a room thermostat.
• Compact wall-mounted design.
• Lower purchase and installation costs compared to the condensing alternative.
• Suitable as a direct replacement for an old atmospheric boiler during renovation.

Technical parameters

Who is the NSK 24 suitable for

We recommend the NSK 24 especially for: heating system renovations where the original chimney is retained and it is not economical to build a new plastic flue system; flats in apartment buildings with a shared chimney shaft, where the technical layout does not allow installation of a condensing boiler; and cases where the priority is a lower purchase price and simple installation over maximum possible efficiency. If you are building from scratch and the flue system can be routed through the facade without restrictions, we also recommend considering condensing models from the KT series (e.g. ACKT20, ACKT28), which will bring long-term gas savings.

Installation and connection

Installation, connection to the chimney, gas piping and the electrical network, as well as initial commissioning, may only be carried out by a professionally qualified person (authorized gas fitter / heating technician). Before installation, the condition and patency of the chimney must be verified by a certified chimney sweep, as the proper function of an atmospheric boiler depends on good chimney draught. The 230 V electrical connection and connection to the heating circuit (flow/return) are standard, as with other ATTACK wall-mounted boilers.

Compatibility and related products

The boiler supports connection of a standard room thermostat with OpenTherm communication (e.g. OT36A or OT36B from the ATTACK range) for more precise heating control based on room temperature.

Maintenance and service

We recommend an annual service inspection by an authorized service provider, including a check of the burner, joint tightness and functionality of safety elements, as well as regular chimney inspection by a chimney sweep in accordance with applicable legislation, since a properly functioning chimney draught is essential for an atmospheric boiler.

Frequently asked questions

Why would I choose an atmospheric boiler instead of a condensing one?

Mainly if you have a functional existing chimney and want to avoid the costs and work involved in building a new plastic flue system – typically during a renovation. A condensing boiler is more efficient in terms of operating costs, but requires a different flue solution.

Is the NSK 24 less efficient than ATTACK's condensing boilers?

Yes, atmospheric technology does not utilize the condensing heat of the flue gases, so seasonal efficiency is lower (approx. 91% compared to approx. 93% for condensing models). In practice this means slightly higher gas consumption for the same heat demand.

Do I need a special plastic chimney for this boiler?

No, quite the opposite – the NSK 24 uses a classic chimney flue with natural draught (type B), which is its main advantage for renovations.

Is a chimney sweep inspection required?

Yes, both before installation and afterwards on a regular basis, the chimney must be inspected and confirmed as compliant by a certified chimney sweep in accordance with applicable regulations.

Can a room thermostat be connected to the boiler?

Yes, the boiler supports connection of a room thermostat with OpenTherm communication from the ATTACK range (OT36A, OT36B).

Is the boiler suitable for a new building as well?

Technically yes, but for a new building where a plastic flue system can be routed through the facade without restrictions, we recommend considering a condensing boiler from the KT series – it will bring lower heating costs in the long run.

What is the difference between "atmospheric" and "non-condensing"?

In this context these are synonyms – an atmospheric boiler burns gas with natural chimney draught and does not utilize the condensing heat of the flue gases, unlike condensing boilers with forced flue exhaust.

What is the warranty on the NSK 24 boiler?

As with other ATTACK gas wall-mounted boilers, we provide a warranty period of 24 months from commissioning, but no more than 30 months from the date of dispatch.

Typical use cases

Replacing an old atmospheric boiler in a flat: In a prefab or older apartment building with a shared chimney shaft, the original gas boiler is reaching the end of its life. Since the building's technical layout does not allow easy installation of a new plastic concentric flue through the facade (shared shaft, apartment building restrictions), the NSK 24 is a direct replacement in the same configuration, using the existing chimney.

Family house after partial renovation: The owner only needs to replace an outdated boiler, while the chimney is in working condition and no facade renovation is planned. The NSK 24 allows for a quick replacement without any work on the building's facade.

Building with a limited heating renovation budget: Where the priority is the lowest possible purchase and installation cost and the existing chimney is functional, the NSK 24 represents a more economical alternative to condensing models, albeit with slightly higher long-term operating costs.

What the regulations say about type B flue systems

Atmospheric boilers with natural draught (type B) depend on a functional chimney and are subject to regular chimney sweep inspections in accordance with applicable chimney legislation. Before installing the boiler, the chimney must be checked by a professionally qualified person (chimney sweep), who will confirm its suitability (patency, draught, tightness) for the given type and output of the appliance. Without this confirmation, the boiler cannot be legally commissioned.

Additional frequently asked questions

What if my existing chimney does not meet the requirements for an atmospheric boiler?

In that case, the chimney needs to be modified (e.g. lined) or an alternative flue solution considered, or the choice reconsidered in favor of a condensing boiler with its own forced flue exhaust – we recommend consulting a chimney sweep and an installation company before purchasing the boiler.

Is the NSK 24 louder or quieter than ATTACK's condensing boilers?

The atmospheric boiler operates with natural draught without a forced flue fan, which can be quieter in some operating modes than a condensing boiler with a fan, although overall noise level is also influenced by the burner and other operating components.

Can the NSK 24 be replaced later with a condensing boiler without modifying the chimney?

Switching to a condensing boiler would require a new type of flue system (concentric or split, with forced exhaust), since the principle of flue gas removal is different – it is therefore not possible to simply replace only the boiler without modifying the flue system.

Can the NSK 24 also be operated on LPG (propane-butane)?

On request, the boiler can be converted to LPG instead of natural gas G20 – such conversion must always be carried out exclusively by an authorized service technician with the appropriate certification.

How often does an atmospheric boiler need servicing?

The recommended interval is one service inspection per year by an authorized service provider, along with regular chimney sweep inspections in accordance with applicable regulations.

Why is this model called "New"?

The NSK 24 is a new model in the ATTACK range, complementing the portfolio with a simpler atmospheric alternative alongside the established condensing KT, KST and KZT series, specifically for situations where an atmospheric solution is technically or economically more advantageous.

Is a room thermostat included in the delivery?

No, the room thermostat is ordered separately – from the ATTACK range we recommend the OT36A (wireless) or OT36B (wired) models, both compatible thanks to OpenTherm communication.

What is the expected impact on gas bills compared to a condensing boiler?

Due to the lower seasonal efficiency (approx. 91% compared to approx. 93% for condensing technology), slightly higher gas consumption can be expected for the same heat demand. The exact difference depends on the specific building, heating method and system settings.

Can the NSK 24 be ordered in a different output version?

Currently the NSK 24 model is available on atria.sk in the output range of 8 – 24 kW described in this product. If you need a different output, we recommend contacting our customer center for the current offer of other models in the ATTACK range.

Do you also provide installation for this boiler?

Installation of the boiler is carried out by ATTACK's contracted authorized service partners in the given region – we will be happy to recommend a suitable installation partner for your location.

Warranty

For the ATTACK gas wall-mounted boiler, we provide a warranty period of 24 months from commissioning by an authorized ATTACK service technician, but no more than 30 months from the date of dispatch from the manufacturer's warehouse (whichever occurs first). The warranty is valid subject to professional installation, initial commissioning by an authorized ATTACK service provider, and compliance with regular annual service inspections according to the operating manual. Without confirmed commissioning, the warranty period is calculated from the date the boiler is dispatched from the factory, but not exceeding the stated 30 months.

The ATTACK Atmospheric NSK 24 is an honest, simple choice for renovations and situations where a chimney flue is already available and the priority is a simple, quick and affordable replacement of an old boiler with a new one.

Summary

The NSK 24 is not a substitute for condensing technology where a new plastic flue system can easily be installed – in that case, it is worth choosing a condensing boiler from the KT series in the long run. However, where the priority is keeping the existing chimney, a simple and quick replacement without any work on the facade, and a lower purchase price, the NSK 24 offers an honest and functional solution without hidden compromises – we can tell you exactly what you gain and what you give up with this decision compared to the condensing alternative, and we are happy to help you choose the right option for your specific building.

Comparison summary in brief

We choose a condensing boiler when a new flue system is easy to install and the priority is the lowest possible long-term gas consumption. We choose the atmospheric NSK 24 when a functional chimney already exists, facade modifications are undesirable or not possible, and the priority is a simple, quick and cost-effective boiler replacement in the same configuration as before.

If you are unsure which type of boiler is more suitable for your specific building, we are happy to advise you before purchase through the atria.sk customer center – just send us basic information about the chimney type, the building layout and the current heating system.

Despite its lower seasonal efficiency compared to condensing technology, this is a proven and reliable type of boiler with a long history of use on the market, supported by a wide network of service technicians experienced with atmospheric appliances.

We supply the boiler together with the basic documentation needed for commissioning registration, and with the support of the atria.sk customer center for any questions before and after purchase.

As with any gas appliance, safe and long-term reliable operation depends primarily on professional installation, correct initial commissioning, and compliance with regular service inspections throughout the boiler's lifetime.

Thank you for taking care in choosing your heating source – a properly chosen boiler will serve you reliably for many years to come.