x-buffer® flex

x-buffer flex – layered buffer storage tank. Specifically for use with heat pumps.

The heat storage tank has been specifically developed for use with heat pumps. In conjunction with the integrated inflow dampers, the two temperature levels for hot water and heating ensure optimum temperature stratification and ensure that the generated heat is stored efficiently. Additional connections on both sides allow flexible integration of further heat generators on site.

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Layered buffer storage tank

x-buffer flex

The high-quality, 130 mm thick, 2-layer insulation made of 110 mm EPS and 20 mm fleece reduces storage losses to a minimum. The small tilt and door frame dimensions and the perfectly matched system components make for simple, fast, and error-free installation.

The layered buffer storage tank impresses with its modern design and by allowing flawless installation of the hydro module in a quick and self-explanatory way.

  • Storage capacity of 620 to 1300 litres

  • Connections are available for additional heat generators, solar integration, and accessories

  • Space-saving combined solution for heating and hot water

  • Clear construction, quick and easy installation

  • All electrical components are completely prewired

  • Flexible routing of cables on site

  • Ideal for operation with heat pumps.

  • Flexible wall mounting on left or right

  • All pipes between the storage tank and hydraulic tower that are included with delivery can be installed quickly with flat-sealing connections

  • Maintenance only from the front

Der Wärmespeicher wurde speziell für den Einsatz mit Wärmepumpen entwickelt - für Warmwasser und Heizung
For x-change dynamic AW E / AW I / BW I / WW I

Hydro module

When combined with an x-buffer flex layered buffer storage tank, the hydro module is used to charge the storage tank, to heat domestic water, and to supply the heating surfaces with thermal energy.

Buffer charging assembly

  • Speed-controlled circulation pump: Wilo Para G 25/8 iPWM 1

  • 2 switching valves

  • Actuator: ESBE ARA 551, 60 s, 230 V

  • Flow and return shut-off valves along with integrated gravity brake

  • Heat pump connection: internal thread R 1 ¼", axial distance 125 mm

Heating circuit

  • Circulation pump WILO Para G 25/6 SC or WILO Para G 25/9

  • Mixing valve with actuator ESBE ARA 551, 60 s, 230 V (only with mixed heating circuit)

  • Heating system connection: internal thread R 1", axial distance 125 mm

  • Flow and return shut-off valves with integrated thermometer, sensor sleeve (only for mixed heating circuit), and gravity brake

Fresh water station

  • Electronically controlled hot water generation

  • Choice of Copper Soldered or Stainless Steel Soldered stainless steel heat exchanger (depending on water quality)

  • Modbus interface for direct communication with the Kermi x-center pro control

Domestic water circulation (optional)

  • For increased hot water comfort

  • Circulation control on request or individual time programs

Storage tank layering set (optional)

  • To maintain the storage layering in circulation mode

  • Switching valve type: ESBE SLB 136 24 V

  • Recommendation: The storage tank layering set is recommended for large systems according to DVGW W 551 and for small systems with greater circulation loads, e.g. old buildings, time control, and so on …

For x-change dynamic pro ac

Hydro module pro

x-center pro heat pump control

On the hydro module pro, the x-center pro heat pump control is also integrated into the module with a display. The layered buffer storage tank has been specially designed for use with the x-change dynamic pro heat pump.

  • Integrated control components incl. contactors for screw-in radiators

  • High-resolution, capacitive 7" colour touch display

  • All components prewired at the factory


heat storage

Not all of the energy generated by the heat pump always gets used immediately. In this case, it makes sense to store the heat generated from renewable energy sources efficiently and with the lowest possible losses. That makes heat storage an important component of any future-oriented heating system.

Whether we are talking about making rooms warm and cosy or providing hygienic domestic water: Heat storage is an important element of all modern heating systems.

Buffer storage systems

Buffer storage tanks keep heat generation and heat consumption completely separate. This means that heat is generated regardless of when it is consumed and your heat pump does not have to start up again every time you turn up a radiator, for example.

Hot water storage systems

Hot water storage tanks ensure that there is always enough hot water available, even if everyone wants a bath.

As with buffer storage tanks, generation and consumption are once again kept separate.

Combined storage tanks

Combined storage tanks incorporate buffer storage and hot water storage in one unit.

The two types of storage are kept strictly separate from one another. Combined storage is the optimal solution if you don’t have much space in the cellar but still want to have an efficient and environmentally friendly storage system.

Installation video

The special layering process ensures optimum stratification of water layers at different temperatures within the Kermi x-buffer layered buffer storage tank.

This process, which has a patent pending, all but eliminates turbulence so that virtually no mixing of cold and warm water can occur. The water flows into the storage tank slowly and can rise or sink, depending on the temperature. Together with the high-quality all-round insulation, this significantly minimises energy losses.

The innovative housing design of the x-buffer layered buffer storage tank makes it a great space-saving alternative.

The system takes up no more room than a conventional heating tank. Thanks to the special base design, the tilt dimension (when the tank is tilted diagonally) barely exceeds the installation height. As a result, the x-buffer layered buffer storage tank also differs from conventional storage models in terms of its external appearance and is absolutely ideal for low-ceilinged rooms in existing buildings. With the intelligent arrangement of the connections, the x-buffer also fits through narrow doors.


Fresh water station

The fresh water station for wall mounting is available in 4 different versions.

The electronically controlled hot water generation relies on the continuous flow principle, ensuring that hot water is heated as hygienically as possible and in line with demand.

The speed-controlled charge pump regulates the set tap temperature quickly and efficiently.

The Modbus interface for direct communication with the Kermi® x-center® control ensures maximum operating comfort via the heat pump control – optionally, up to 4 fresh water stations can be combined in a cascade

Fresh water station cascade set

A cascade set is needed for each additional fresh water station.

A maximum of four fresh water stations can be combined in total.

To install a fresh water cascade, you need a fresh water station with circulation to serve as the master; each additional slave station is then implemented without circulation.

Storage charging assembly

The storage charging assembly for wall mounting is available in different versions.

The integrated storage charging pump is speed-controlled (PWM) so that charging with the modulating x-change dynamic (pro) heat pump series can take place efficiently and in line with demand in every operating mode.

The components are pre-assembled on a platform and the insulation is already incorporated as well.

Heating circuit assembly

The “unmixed heating circuit” assembly consists of a circulation pump (delivery head of 6 m or 9 m) and the corresponding shut-off devices.

The “mixed heating circuit” assembly also has a mixer.

These components are pre-assembled on a platform and the insulation is already incorporated as well.

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