ATTACK Condensing KT gas condensing boiler

30 years of development and manufacturing

ATTACK Condensing KT 20/28 gas condensing boiler

Wall-mounted boiler that can be connected to an external DHW tank.

The boiler provides heating and, with a flexible hot water tank connection, can meet the needs of a larger household. Modulation of up to 1:10 and the intelligent ISC combustion system help reduce gas consumption. The boiler can also be controlled according to the outdoor temperature using weather-compensated control.

Output

KT 20: 2.4–25 kW
KT 28: 3.3–33.2 kW

Domestic hot water preparation

External tank

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Category: Gas boilers

1:10modulation range

ISCcombustion control

up to 106%stated efficiency

H₂ ReadyReady for a natural gas and hydrogen blend

Discover ATTACK Condensing gas boilers

Two output variants

Explore the KT 20 and KT 28 output options, their connections and heating features.

A family home in winter, suitable for heating with an ATTACK gas boiler

For homes and apartments

Suitable for all types of homes and apartments

With an output of up to 29.5 kW, the boiler can heat a family home of up to 400 m². Any DHW tank can be connected to the boiler. Available tank volumes range from 80 to 200 litres.

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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 KT 20/28 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 KT 20/28 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.

Comfortable heating with hot water

Heating output for a home with an external tank

ATTACK Condensing KT 20/28 is a wall-mounted boiler for heating. When connected to a separate tank, it also prepares domestic hot water. Weather-compensated control can adjust the boiler according to the outdoor temperature.

Technical features of ATTACK Condensing KT 20/28

Discover the ATTACK Condensing KT 20/28 condensing boiler

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

ISC

Intelligent combustion system

The intelligent combustion system regulates combustion and adjusts settings such as gas flow to maintain the correct air-to-gas ratio.

Reduced gas consumption
Lower CO₂ emissions
Less time needed to install and set up the boiler
Modulation range of 1:10
Fewer on/off cycles
Longer boiler service life

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.

Gas boiler options for ATTACK Condensing KT 20/28

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 KT 20/28 boiler components

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

Labelled cutaway of the ATTACK Condensing KT 20/28 boiler

Komponent 01 / 11

Air intake

Supplies the air required for combustion.

Komponent 02 / 11

Flue-gas outlet

Carries flue gases away from the boiler combustion chamber.

Komponent 03 / 11

Condensing heat exchanger

Transfers heat from the flue gases to the heating water.

Komponent 04 / 11

Gas valve

Regulates the gas supply required for combustion.

Komponent 05 / 11

Condensate trap

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

Komponent 06 / 11

Modulating pump

Circulates heating water through the hot-water heating system.

Komponent 07 / 11

Three-way valve

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

Komponent 08 / 11

Mixer

Creates the gas mixture used for combustion.

Komponent 09 / 11

Burner

The gas mixture burns on its surface, releasing heat.

Komponent 10 / 11

Fan

Supplies the gas mixture to the burner.

Komponent 11 / 11

Pressure relief valve

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

Detailed specifications

Technical data

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

Parameter	Unit	ATTACK Condensing KT 20/28

Product materials

Download documents

ATTACK Condensing KT 20/28 operating manual PDF · SK ATTACK Condensing KT 20/28 operating manual — 2023 edition PDF · SK OT80 thermostat operating manual PDF · SK/EN OT81 Wi-Fi modem operating manual PDF · SK/EN ATTACK Condensing KT 20 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

How does a gas boiler work?YouTube

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 KT 20/28 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.

Request a free quote

ATTACK Condensing KT 20/28 gas condensing boiler

Wall-mounted boiler that can be connected to an external DHW tank.

Suitable for all types of homes and apartments

Boiler connection

Why choose a condensing boiler?

Why choose a gas boiler?

H₂ Ready

Heating output for a home with an external tank

Intelligent combustion system

Stainless-steel heat exchanger

Quality components

Frost protection

Bacteria protection

Cascade connection option

OpenTherm control

SMART control

Air intake

Flue-gas outlet

Condensing heat exchanger

Gas valve

Condensate trap

Modulating pump

Three-way valve

Mixer

Burner

Fan

Pressure relief valve

Choosing and installation support

Is ATTACK Condensing KT 20/28 right for your home?

Would you help us improve?