CLESS 1S: high-stratification buffer tank for technical heat storage
CLESS 1S is the technical heat-storage configuration within the CLESS range developed by REQA.
The system uses special compensation chambers to manage water flows between the heat generator, buffer tank and heating circuit, reducing mixing between hot and cold water and supporting thermal stratification inside the storage tank.
Patented compensation-chamber system
The operating principle of CLESS differs from that of a conventional storage tank.
The internal compensation chambers manage water flow between the heat generator and the heating circuit, allowing the thermal energy produced to be used according to the actual operating conditions of the system.
Generator and heating circuit with the same flow rate
The compensation chambers allow thermal flow exchange between the heat generator and the heating circuit.
The generator produces more energy than required
Excess heat is transferred to the storage tank and the hot water is directed towards the upper section of the buffer tank.
The heating system requires energy from the buffer tank
The heating circuit can use the hot water stored in the upper section of the tank, where the highest thermal energy is concentrated.
By-pass system: heat is used where it is needed
Thanks to its specific flow-management system, CLESS can transfer heat from the generator to the heating circuit without necessarily requiring the entire storage volume to be heated beforehand.
When thermal output exceeds the immediate demand of the heating system, the excess energy is progressively stored inside the buffer tank.
The system therefore combines thermal energy storage with dynamic flow management between the heat generator and the heating circuit.
Heat generator protection and return-flow management
The compensation-chamber system helps prevent the heat generator from directly receiving the coldest water stored at the bottom of the buffer tank.
The return flow towards the generator is instead managed using the water returning from the heating circuit, helping to reduce sudden thermal variations affecting the generator.
Solar thermal heat exchanger included as standard
Solar thermal integrationCLESS 1S includes a dedicated solar heat exchanger, allowing thermal energy produced by solar collectors to be transferred to the buffer tank.
The storage tank can therefore be installed in systems where solar thermal works together with other heat generators.
The solar heat exchanger allows the energy produced during favourable solar conditions to be stored and subsequently used by the heating system.
Three versions: CLESS 600, 800 and 1000 1S
CLESS 1S is available in three different sizes. The commercial designation identifies the model, while the actual useful volume is shown in the technical table.
| Specification | CLESS 600 1S | CLESS 800 1S | CLESS 1000 1S |
|---|
| Useful volume | 510 l | 738 l | 945 l |
| Energy class | C | C | C |
| Heat loss | 112 W | 130 W | 144 W |
| Solar heat exchanger surface | 2.5 m² | 2.5 m² | 3 m² |
| Solar heat exchanger pressure drop | 73 mbar | 191 mbar | 313 mbar |
| Empty weight | 187 kg | 208 kg | 234 kg |
| Max. buffer tank operating pressure | 3 bar | 3 bar | 3 bar |
| Max. solar heat exchanger operating pressure | 10 bar | 10 bar | 10 bar |
| Max. operating temperature | 90 °C | 90 °C | 90 °C |
| REQA product code | 304.001 | 304.002 | 304.003 |
CLESS 1S dimensions
| Dimension | 600 1S | 800 1S | 1000 1S |
|---|
| Diameter without insulation | 650 mm | 790 mm | 790 mm |
| Overall diameter | 850 mm | 990 mm | 990 mm |
| Overall height | 1765 mm | 1725 mm | 2175 mm |
100 mm thermal insulation
CLESS uses 100 mm thick recycled polyester-fibre insulation, designed to reduce thermal losses.
Insulation: recycled polyester fibre
Thickness: 100 mm
Outer covering: PVC Seta Skin
Maximum operating temperature: 90 °C
Does CLESS 1S produce domestic hot water?
No. CLESS 1S is the technical heat-storage configuration within the range and does not include a heat exchanger for domestic hot water production.
If instantaneous DHW production is also required, the CLESS 2S or CLESS+ 2S configurations should be considered according to the type of heat generator used.
When should you choose CLESS 1S?
CLESS 1S is suitable when a high-stratification technical buffer tank is required without direct domestic hot water production.
- heating systems requiring technical heat storage;
- systems with multiple heat generators;
- systems equipped with solar thermal collectors;
- systems where domestic hot water is managed separately;
- properly designed hybrid heating systems.
Frequently asked questions about CLESS 1S
What is the difference between CLESS 600, 800 and 1000 1S?
The three versions mainly differ in useful volume, dimensions, weight and solar heat exchanger surface. Their useful volumes are 510, 738 and 945 litres respectively.
Does CLESS 1S include a solar heat exchanger?
Yes. All CLESS 1S versions include a dedicated heat exchanger for the solar thermal circuit.
Does CLESS 1S produce DHW?
No. CLESS 1S does not include a domestic hot water heat exchanger.
Can CLESS 1S be used with a pellet boiler?
CLESS can be integrated into systems with biomass heat generators. The final system configuration and correct buffer sizing must be checked according to the characteristics of the heat generator and the heating system.
How should I choose between CLESS 600, 800 and 1000 1S?
The storage capacity should be selected according to the type and output of the heat generator, the building's heating demand, the characteristics of the heating circuit and the overall system configuration.
Advice and orderingCLESS 1S can be ordered in 600, 800 and 1000 versions. Contact our customer service team to check correct sizing, system configuration and delivery times.
System sizing and configuration must be checked by a qualified technician. Always refer to REQA technical documentation and applicable regulations.
