ATTACK Condensing KZT 25 gas condensing boiler

30 years of development and manufacturing

ATTACK Condensing KZT 25 gas condensing boiler

Condensing boiler with an integrated 60-litre tank.

The boiler combines efficient heating with convenient hot water preparation. Its integrated 60-litre DHW tank and intelligent ISC system provide comfort and efficient operation. Modulation of up to 1:10 adapts output to current demand and helps reduce gas consumption. A practical solution for homes with higher DHW demand.

Model

KZT 25: 2.6–26 kW

Integrated tank

60 l

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Category: Gas boilers

1:10modulation range

Smart control

up to 106%stated efficiency

SPA PLUSrapid water reheating

Discover ATTACK Condensing gas boilers

Heating output and comfort for your home

Discover the ATTACK Condensing KZT 25, its output, integrated DHW tank and control options.

Family home suitable for heating with an ATTACK gas boiler

For homes and apartments

Heating and hot water comfort in one boiler

ATTACK Condensing KZT heats family homes and smaller commercial premises. Its integrated 60-litre stainless-steel tank with the SPA PLUS function provides convenient DHW heating, while output modulation of up to 1:10 helps match performance to current demand.

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Connecting an ATTACK gas boiler to natural gas or propane

Gas

Boiler connection

A condensing gas boiler needs a connection to natural gas, one of the lower-emission fossil fuels. If natural gas is unavailable, the boiler can be connected to propane instead.

ATTACK Condensing KZT 25 can run on different gas types (G20 natural gas or G31 propane). Fuel conversion and adjustment must be carried out by an ATTACK service technician.

Benefits

Why choose a condensing boiler?

Why choose a gas boiler?

The initial cost is low compared with biomass boilers or heat pumps. Gas boilers are among the more affordable heating options and require little maintenance.

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Fuel

H₂ Ready

ATTACK Condensing KZT 25 is ready for the heating systems of the future. H₂ Ready technology lets it operate on a natural gas blend containing up to 20% hydrogen. The ISC system assesses combustion quality by measuring flame ionisation, helping to control it precisely.

Integrated DHW heating

SPA Plus function

ATTACK Condensing KZT 25 combines heating with an integrated 60-litre stainless-steel domestic hot water tank. The SPA PLUS function speeds up water reheating.

Internal components of the KZT 25 boiler

Technical features of ATTACK Condensing KZT 25

Discover the ATTACK Condensing KZT 25 condensing boiler

Explore the intelligent combustion system, stainless-steel heat exchanger, quality hydraulic assembly and features that protect the boiler and tank.

Combustion and integrated tank in the ATTACK KZT 25 gas boiler

SPA PLUS

SPA Plus function

The PLUS function keeps hot water ready for immediate use. The integrated 60-litre tank comfortably serves higher or simultaneous demand, and the boiler reheats the water after use.

Heat exchanger

Stainless-steel heat exchanger

ATTACK Condensing KT uses a stainless-steel heat exchanger with extra-wide channels, whose cross-section is up to four times larger than that of standard exchangers. This supports efficient heat transfer and helps resist the build-up of dirt. It is also a suitable option when replacing a boiler in an existing heating system.

Hydraulic assembly

Quality components

The new brass hydraulic assembly is equipped with:

A high-efficiency pump
A three-way valve
A bypass
A flow regulator with a filter
A drain valve
A domestic hot water temperature sensor

Burner flame in an ATTACK condensing gas boiler

Protection

Frost protection

Frost protection keeps your boiler protected on cold days. If it remains connected to the gas and electricity supplies, the burner starts automatically and the pump switches on when the temperature falls below 6 °C. This function helps protect the boiler and extend its service life.

Water in the tank heated by the Anti-Legionella function

Water protection

Bacteria protection

The Anti-Legionella function automatically heats the water in the DHW tank at regular intervals. At least once a week, it heats the water to 65 °C, regardless of the thermostat setting. Legionella bacteria thrive in water at 25–55 °C, while heating it above 60 °C destroys them, so this function helps reduce the risk of their growth.

ATTACK Condensing KZT 25 gas boiler options

Enjoy even greater comfort

Explore cascade connection and mobile control options for the gas boiler.

Cascade connection of ATTACK Condensing KT boilers

Cascade connection option

Can be connected in a cascade

ATTACK Condensing KT boilers are designed to support cascade connections of up to four boilers. A cascade controller, available as an accessory, is required. The cascade controller intelligently manages the connected boilers and gives you full control of the system.

ATTACK gas boiler with OpenTherm thermostats

OpenTherm control

OpenTherm control (optional accessory)

OpenTherm control does more than switch the boiler on. It compares the actual room temperature with the set temperature, allowing the boiler output to respond to the heating demand. OpenTherm control helps lower consumption, maintain a steadier temperature and improve comfort.

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Remote control of an ATTACK gas boiler through a mobile app

SMART control

Smart remote control

Optional accessories include the OT80 OpenTherm room thermostat and OT81 Wi-Fi modem. Together with the ATTACK Condens mobile app, they let you control the boiler remotely.

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Technical information about boiler components

ATTACK Condensing KZT 25 boiler components

This interactive map is based on the labelled cutaway and component descriptions on the ATTACK product page.

Labelled cutaway of the ATTACK KZT 25 gas boiler

Komponent 01 / 14

Gas valve

Regulates the gas supply required for combustion.

Komponent 02 / 14

Flue-gas outlet

Carries flue gases away from the boiler combustion chamber.

Komponent 03 / 14

Condensing heat exchanger

Transfers heat from the flue gases to the heating water.

Komponent 04 / 14

Condensate trap

Acts as an odour trap and prevents smells from the combustion chamber entering the external drain.

Komponent 05 / 14

Burner

The gas mixture burns on its surface, releasing heat.

Komponent 06 / 14

Modulating pump

Circulates heating water through the hot-water heating system.

Komponent 07 / 14

Pressure relief valve

A safety device that reduces pressure in the heating system if it becomes excessive.

Komponent 08 / 14

Filling valve

Adds water to the heating system.

Komponent 09 / 14

Three-way valve

Directs heating water either to the heating system or to the heat exchanger that heats domestic hot water.

Komponent 10 / 14

Fan

Supplies the gas mixture to the burner.

Komponent 11 / 14

Venturi tube

Creates the gas mixture used for combustion.

Komponent 12 / 14

Central-heating expansion vessel

The 2-litre vessel compensates for changes in water volume as it heats and helps protect the heating system from excessive pressure.

Komponent 13 / 14

DHW expansion vessel

The 10-litre vessel compensates for changes in water volume as it heats and helps protect the system from excessive pressure.

Komponent 14 / 14

DHW tank

The 60-litre stainless-steel tank heats potable water and stores it for household use.

Detailed specifications

Technical data

Check the manufacturer's current documentation before designing the heating system.

Parameter	Unit	ATTACK Condensing KZT 25

Product materials

Download documents

ATTACK Condensing KZT 25/35 operating manual PDF · SK OT80 thermostat operating manual PDF · SK/EN OT81 Wi-Fi modem operating manual PDF · SK/EN ATTACK Condensing KZT 25 energy label PDF · SK ATTACK Condensing KT/KST/KZT declaration of conformity PDF · SK Technical data PDF

Videos

Take a closer look at the boiler

ATTACK condensing boilersYouTube

Customer support

Choosing and installation support

ATTACK service partners can help design, install and maintain the heating system. Ask an expert to assess whether the boiler and chimney are suitable.

Service support

Output selection should be handled by an expert

Is ATTACK Condensing KZT 25 right for your home?

Send us some details about your home and heating system. We will connect you with an expert partner who can check the design and installation.

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ATTACK Condensing KZT 25 gas condensing boiler

Condensing boiler with an integrated 60-litre tank.

Heating and hot water comfort in one boiler

Boiler connection

Why choose a condensing boiler?

Why choose a gas boiler?

H₂ Ready

SPA Plus function

SPA Plus function

Stainless-steel heat exchanger

Quality components

Frost protection

Bacteria protection

Cascade connection option

OpenTherm control

SMART control

Gas valve

Flue-gas outlet

Condensing heat exchanger

Condensate trap

Burner

Modulating pump

Pressure relief valve

Filling valve

Three-way valve

Fan

Venturi tube

Central-heating expansion vessel

DHW expansion vessel

DHW tank

Choosing and installation support

Is ATTACK Condensing KZT 25 right for your home?

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