CLESS+ 2S: high-stratification buffer tank for heat pumps
CLESS+ 2S is the CLESS configuration developed for integration with heat pumps.
It combines high-stratification technical heat storage, instantaneous domestic hot water production, solar thermal integration and dynamic flow management through the patented compensation-chamber system.
Designed for heat pump systems
CLESS+ 2S provides thermal storage between the heat pump and the heating system, allowing generated energy to be stored and supplied according to heating demand.
Defrost management
Energy stored in the buffer tank can help maintain heating comfort during heat pump defrost cycles.
Stable supply temperature
Thermal storage contributes to more stable operating conditions for the heating circuit and heat pump.
Reduced compressor micro-cycling
The buffer tank helps reduce excessively frequent heat pump compressor start and stop cycles.
Patented compensation-chamber system
The core of CLESS technology is the compensation-chamber system, designed to manage water flows between the heat generator, buffer tank and heating circuit.
The system reduces mixing between areas at different temperatures and supports thermal stratification inside the buffer tank.
When heat production matches heating demand
The compensation chambers allow thermal flow exchange between the heat pump and the heating circuit.
When more energy is produced than required
Excess thermal energy is transferred to the storage tank, with hot water directed towards the upper section of the buffer.
When the heating system requires stored energy
The heating circuit can use hot water stored in the upper section of the tank, where thermal stratification concentrates the available energy.
Enlarged DHW heat exchanger for heat pump applications
A key feature of CLESS+ 2S is its enlarged heat exchanger for instantaneous domestic hot water production.
| Model | DHW exchanger surface | DHW production* |
|---|
| CLESS+ 600 2S | 4 m² | 2 m³/h |
| CLESS+ 800 2S | 5 m² | 2.5 m³/h |
*DHW production specified with domestic water from 10 to 45 °C and storage temperature at 70 °C.
Instantaneous domestic hot water productionThe removable DHW heat exchanger is positioned in the upper section of the storage tank, where thermal stratification concentrates the highest available temperatures.
Solar thermal integration
CLESS+ 2S also includes a dedicated solar thermal heat exchanger as standard.
The buffer tank can therefore receive thermal energy from both the heat pump and solar collectors, allowing different energy sources to be integrated within the same heating system.
Integration with photovoltaic systems
In a system equipped with photovoltaic panels, the heat pump can use electricity generated by the PV system to produce heat and transfer it to the CLESS+ 2S.
The buffer tank can therefore operate as a thermal energy store, retaining energy in the form of heat for subsequent use by the heating system.
CLESS+ 2S technical specifications
| Specification | CLESS+ 600 2S | CLESS+ 800 2S |
|---|
| Useful volume | 510 l | 738 l |
| Energy class | C | C |
| Heat loss | 112 W | 130 W |
| DHW heat exchanger surface | 4 m² | 5 m² |
| DHW production 10/45 °C with storage at 70 °C | 2 m³/h | 2.5 m³/h |
| DHW heat exchanger pressure drop | 584 mbar | 953 mbar |
| Solar heat exchanger surface | 2.5 m² | 2.5 m² |
| Solar heat exchanger pressure drop | 73 mbar | 191 mbar |
| Empty weight | 207 kg | 229 kg |
| Max. buffer tank operating pressure | 3 bar | 3 bar |
| Max. DHW heat exchanger operating pressure | 3 bar | 3 bar |
| Max. solar heat exchanger operating pressure | 10 bar | 10 bar |
| Max. operating temperature | 90 °C | 90 °C |
| REQA product code | 304.007 | 304.008 |
CLESS+ 2S dimensions
| Dimension | CLESS+ 600 2S | CLESS+ 800 2S |
|---|
| Diameter without insulation | 650 mm | 790 mm |
| Overall diameter | 850 mm | 990 mm |
| Overall height | 1765 mm | 1725 mm |
| Domestic cold water inlet | 3/4" | 3/4" |
| Domestic hot water outlet | 3/4" | 3/4" |
100 mm thermal insulation
CLESS uses 100 mm thick recycled polyester-fibre insulation, protected by a PVC Seta Skin outer covering.
When should you choose CLESS+ 2S?
CLESS+ 2S is the configuration to consider when the system uses a heat pump and instantaneous domestic hot water production is also required.
- heat pump systems;
- instantaneous DHW production;
- solar thermal systems;
- systems combining photovoltaic power and a heat pump;
- systems requiring technical heat storage to support heat pump operating cycles.
Frequently asked questions about CLESS+ 2S
Is CLESS+ 2S designed for heat pumps?
Yes. REQA identifies CLESS+ 2S as the CLESS configuration featuring an enlarged DHW heat exchanger for heat pump applications.
What is the difference between CLESS 2S and CLESS+ 2S?
Both provide domestic hot water production, but CLESS+ 2S uses an enlarged DHW heat exchanger: 4 m² on the 600 model and 5 m² on the 800 model. It is the configuration intended for heat pump applications.
Does CLESS+ 2S produce domestic hot water?
Yes. Domestic hot water is heated instantaneously through a dedicated removable heat exchanger.
Does CLESS+ 2S include a solar heat exchanger?
Yes. Both versions include a 2.5 m² solar thermal heat exchanger.
What is the DHW production capacity?
With domestic water heated from 10 to 45 °C and the storage tank at 70 °C, the manufacturer specifies 2 m³/h for CLESS+ 600 2S and 2.5 m³/h for CLESS+ 800 2S.
Which model should I choose, 600 or 800?
The correct size depends on the output and characteristics of the heat pump, the building's thermal demand, domestic hot water requirements and the overall system configuration.
Advice and orderingCLESS+ 2S can be ordered in 600 and 800 versions. Contact our customer service team to check correct sizing, system configuration and delivery times.
Storage sizing and system configuration must be checked by a qualified technician. Always refer to REQA technical documentation and applicable regulations.
