Wall-Hung Condensing Combi Boiler

Wall-Hung Condensing Combi Boiler, CLAS ONE | Ariston
24kW, 30kW, and 38kW models available
The Clas ONE boasts Ariston’s patented Xtratech™ stainless steel heat exchanger for better heating and better reliability.
Xtratech™ has a single coil design with 142% wider waterways* to prevent the risk of debris blockage, and an overall improved water flow. With this beast at its heart, the Clas ONE is powerful, but also extremely smart. Its 1:7 modulation ratio means it can adapt to provide the desired heating and hot water, while simultaneously keeping fuel bills low.
The Clas ONE is easy to operate through its back-lit display and is compatible with Ariston controls for use with the Ariston Net app.

  • Xtratech™ stainless steel heat exchanger
  • High domestic hot water flow rates“Auto” function technology
  • Comfort function
  • High efficiency pump
  • 1:7 modulation ratio
  • Quiet operation starting at 49dB
  • Lightweight unit starting at 29kG
  • 8-year warranty
  • “A” ErP rated for optimum energy efficiency
  • Large backlit display
  • Includes LPG conversion kit
  • Ariston NET compatible

 * compared to current industry standard heat exchangers











  • Installation and Maintenance
    • Lightweight and easy to install
      With weights starting from just 28.5kg, it is easy to hang this boiler on the wall, while installation is straightforward, thanks to the simple to fit connections, wiring and flue.
    • Extra space
      There is more room inside for engineers to work on the boiler, aiding installation, commissioning, servicing and repair, with easy frontal access to all components.
    • Robust
      The boiler benefits from a strong and durable chassis, with no sharp edges.
    • Colour coded
      Installing accessories is made even more straightforward thanks to the unique coding system where parts will only fit in the slots of a matching colour.
    • Ariston branded components
      Major components are now Ariston branded for complete confidence in quality. Accept no imitations!
    • Upgrade existing Ariston boilers
      Fully compatible with Ariston’s current range of accessories, the new boiler also has all connections in the same places – enabling an easy retrofit in place of an existing Ariston boiler.
  • Usability and Controllability
    • Quieter running
      A new and improved silencer and the latest soundproofing technology ensure this boiler range is the quietest Ariston has ever produced, with noise levels at 49-52dB across the range. These levels are similar to those of a domestic fridge freezer.
    • Easy to set up
      Low voltage connections, colour coded wiring and a well-designed circuit board ensure it is easy to set up and pair the boiler with the latest Ariston controls.
    • Easy to use
      A clear display panel with intuitive buttons and stunning fascia has been designed with ease of use in mind.
    • Full range of controls
      Ariston’s latest wired and wireless controls are easy to operate, offering end users energy management tips, alongside modern styling.
    • Zoning
      Full zone management kits are available, with the latest Ariston controls capable of managing up to six separate heating zones.


Stainless steel heat exchangers are exceptionally robust and operate well in a wide range of pH values, providing resistance to corrosion.

142% wider waterways
Wider pipes allow water to pass through the heat exchanger more effectively, with less risk of blockages from debris. This extra width also allows hot water to pass through the heat exchanger quicker.

Better transfer of heat
The enhanced single coil heat exchanger is robust and highly efficient, thanks to an improved condensing surface and increased hydraulic performance. This also allows for constant water speeds and a reduced chance of blockages, ensuring a long lifespan.

Continuous coil heat exchanger
Being manufactured from one continuous coil improves energy efficiency while ensuring smoother running of boiler.

TÜV Rheinland certified
Tested and certified for safety, quality and usability by a renowned, independent European body, the TÜV mark offers reassurance to installers and end users alike.


All ONE Series boilers include a built-in ‘AUTO’ function, which enhances boiler performance and aids energy efficiency. It monitors the ideal temperature for the heating system – reducing peaks in flow temperature and optimising efficiency.

Activating the function enables the boiler to automatically choose the ideal output for the central heating circuit, by gradually increasing in power until a room reaches the set temperature, while guaranteeing no excessive peaks.

With the ‘AUTO’ function activated, the boiler consumes less gas and electricity, avoiding on/off cycles and fluctuations in flow temperature. When used alongside the latest heating controls, further savings can be achieved. For example, when used in conjunction with an outdoor sensor with a modulating control, savings in excess of 6% can be achieved compared to a standard condensing boiler without similar controls.


Another function available is ‘COMFORT’ mode, which ensures the water contained inside the secondary (plate to plate) heat exchanger is kept in a pre-heated condition. Turning the ‘COMFORT’ function on ensures the boiler can deliver domestic hot water almost instantaneously when required.

This innovative feature keeps the secondary heat exchanger warmed up, even during periods of inactivity. Benefits of this function include reduced heat up waiting times and less cold water wastage.


An LPG conversion kit is included in the box of every ONE Series boiler. This allows the boiler to be fitted in properties and applications located in off-mains gas areas, while retaining all the benefits associated with Ariston’s high efficiency products.


System Interface
System Interface
System Interface
Outdoor Sensor
Outdoor Sensor
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