Attack CONDENSING KZT 25

Product detailed description

ATTACK CONDENSING KZT 25
- wall-mounted gas condensing boiler with a built-in 60 L stainless steel DHW tank
- output: 2.6 - 26 kW

A condensing boiler with a built-in 60L stainless steel DHW tank and intelligent control for your comfort. The boiler achieves a significant reduction in gas consumption thanks to smooth output modulation of up to 1:10. The ATTACK Condensing KZT 25, with a minimum output from 2.6 - 26 kW, is a great choice for households with high demand for DHW supply. The boiler can also be controlled according to the outdoor temperature (weather-compensated control).

Advantages:

• Energy class for heating A
• Energy class for DHW A - XXL
• High efficiency of up to 107% with gas savings
• Condensing heat exchanger made of stainless steel with extra-wide water channels
• Comfortable hot water preparation of up to 160 - 170L /10min
• Built-in DHW tank 60L
• Higher efficiency thanks to a low number of starts and stops
• High modulation ratio 1:10
• Automatic filling valve
• Programmable setting of the DHW tank charging time
• Simple control
• Brass hydraulic group
• Multifunctional control system, more than 40 configurable parameters
• Safe and easy to use thanks to integrated protective functions
• Digital control panel with a backlit LCD display and self-diagnostics
• Low CO2 and NOx emissions
• NOx Class 6

New heat exchanger
The Condensing KZT 25 gas boiler is fitted with a stainless steel heat exchanger equipped with extra-wide channels, where the internal area has been increased up to fourfold compared to a commonly used heat exchanger. Thanks to the new heat exchanger, better thermal efficiency and better resistance to scale build-up are achieved, making the Condensing KZT 25 ideal even for replacing a boiler in an already existing heating system.

Hot water always available
Thanks to the PLUS function, the boiler always has a ready supply of hot water that you can use immediately. The boiler with the tank is able to satisfy high DHW consumption demands and provide a hot water supply simultaneously in various household situations. Thanks to the 60L stainless steel tank, a large amount of water can be kept ready for use - while the water contained in the tank is being consumed, the boiler quickly reheats the same amount that is stored in the tank.

Powerful control unit
Quality, trouble-free operation of the Condensing KZT condensing boiler is taken care of by modern control electronics. It handles output control, self-diagnostics, and detection of combustion faults. The control unit carefully evaluates all this data and uses it to optimise all the factors that affect overall combustion efficiency.

ISC Intelligent Combustion System
The condensing Condensing KZT 25 boiler is equipped with the Intelligent Combustion System. The only boiler on the market that uses an intelligent combustion system to set its own parameters according to current conditions. The intelligent combustion system controls combustion and adjusts values such as gas flow to always achieve the correct air/gas ratio, which ensures:

• Reduced gas consumption
• Lower CO2 emissions
• Shorter time for boiler installation and setup
• Modulation ratio 1:10
• Perfect combustion
• Extended boiler service life
• Reduced number of on/off cycles
• The boiler can be used with several types of gas (G20 natural gas or G31 propane; the fuel change and setup must be performed by an ATTACK service technician)

Quality and efficiency
In the production of our boilers, we used brass components in the hydraulic assembly to ensure maximum product reliability. The new brass hydraulic group is equipped with:

• A high-efficiency pump
• A three-way valve
• A bypass
• A flow regulator with a filter
• A drain valve
• A DHW temperature sensor

Frost protection
To extend service life, we have integrated a function into the boiler that prevents damage to your condensing boiler due to unfavourable frosty weather. As long as you leave the boiler connected to gas and electricity, it takes care of everything for you. If the temperature drops below 6 °C, the burner ignites by itself and the pump switches on automatically.

Bacteria protection
We have built a special Anti-Legionella function into the condensing boiler, thanks to which you don't need to worry about bacteria multiplying in water they like warm. One of these is Legionella, which thrives at a water temperature of 25-55 °C. The bacterium is killed by heating the water above 60 °C. The Anti-Legionella function takes care of heating the water in the DHW tank to 65 °C at least once a week for you, regardless of your thermostat settings.

Pump seizure protection
During prolonged inactivity, dirt can settle in the pump, which could eventually lead to it seizing up. That's why we added a function to the boiler that keeps the pump clean - if the pump is inactive for 24 hours, the boiler automatically switches it on for about 5 seconds to flush it through.

Comfortable control
If you want to save even more with your condensing boiler and raise the bar of comfort even higher, you can use a weather-compensated controller*, which makes this possible. The controller will adjust the temperature according to the outdoor temperature. The temperature will thus automatically adapt to changes in the household and the outdoor temperature. This method of control can use the boiler's output more efficiently and at the same time save you money on operation. In addition, you gain greater comfort, because the controller takes care of everything for you. 

* the weather-compensated controller is not included with the boiler.

Parameters

Frequently Asked Questions

• How exactly do I choose the output of an ATTACK condensing boiler? The starting point is the calculated heat loss of the heated building (most reliably taken from the project documentation or an energy certificate). If you don't have a project, you can roughly estimate about 60-100 W per m² of floor area for a commonly insulated house built after 2000, or 100-150 W/m² for an older, uninsulated house - the exact figure varies depending on the number of floors, ceiling height, the number and quality of windows, and the building's orientation. A boiler oversized for its output switches on and off more often (so-called cycling), which shortens its service life and reduces efficiency; an undersized boiler, on the other hand, cannot heat the house sufficiently on frosty days.
• Why is a condensing boiler more economical than a conventional one? A condensing boiler additionally uses the heat hidden in the water vapour produced when gas is burned - in a conventional boiler this heat escapes unused through the flue, while in a condensing unit it is cooled below the so-called dew point, the vapour condenses, and the released heat is returned to the heating circuit. Thanks to this, condensing boilers achieve an efficiency of approximately 105-110% relative to the calorific value of the gas, compared to the usual 85-92% for conventional boilers.
• What type of flue does this boiler need? Most modern condensing boilers are so-called “turbo” units (with a sealed combustion chamber) and require a concentric (coaxial) or separate flue gas outlet and combustion air intake routed through an outer wall or the roof - so a functioning chimney is not needed. The exact type and maximum length of the flue (depending on the 60/100 or 80/125 mm diameter) can be found in the technical documentation for the specific model, or you can consult our customer service.
• What does the ErP energy class stated for the boiler mean? This is a mandatory efficiency label for heating appliances under the EU ErP (Ecodesign) directive, similar to the energy labels used for refrigerators. Condensing boilers commonly achieve class A, or even higher in combination with room controls (e.g. A+ when using weather-compensated control and a room thermostat).
• Can I install and connect this boiler myself? No. Connection to the natural gas supply, the electrical network, and the flue is by law reserved exclusively for a person with the appropriate qualification (usually an authorised service technician for the given brand or a certified gas appliance inspector). After installation, the boiler must be commissioned by the manufacturer's authorised service, which is usually also a condition for the warranty to be valid.
• What about servicing and the warranty? Most manufacturers require a regular annual service inspection by an authorised service provider in order for the warranty to remain valid even after its standard expiry (an extended warranty subject to regular servicing is common especially with the brands Vaillant, Protherm, and Viessmann). The exact warranty terms can be found in the warranty certificate supplied with the boiler.
• What is included in the delivery of this specific product? The exact package contents (the boiler itself, possibly a hot water tank, room controls, and other accessories in the case of a set) are stated in the product name and in its technical parameters above on this page.