EN 806 Standard: DHW flow rate and thermal storage

The design of plumbing systems in residential and commercial buildings requires precise regulatory references to ensure reliable service. In this context, the EN 806 standard (UNI EN 806 in Italy) represents the European standard for system sizing, focusing in particular on the correct definition of the design flow rate.

The role of EN 806-3 and EN 806-4

The EN 806 series is divided into several parts, each dedicated to a specific phase of the system's lifecycle:

• UNI EN 806-3: Provides the criteria for pipe sizing, based on a simplified method that uses Load Units (LU) for each sanitary fixture.
• UNI EN 806-4: Addresses installation specifications and supply systems.

The application of EN 806-4 is essential for calculating the design flow rate, that is, the theoretical instantaneous peak representing the most demanding realistic case. This probabilistic approach avoids simply adding up all outlets, taking into account that not all draw-off points operate simultaneously.

From flow rate peaks to storage strategy

The calculation of the design flow rate according to the standard often highlights a critical issue: the presence of very high consumption peaks concentrated in short time frames, typical of hotels, gyms, and hospitality facilities.

Although the standard defines how much water must be able to flow through the system, the challenge for the designer remains the efficient management of this energy. When the required flow rate is high, the generator alone (such as a heat pump) would risk being oversized just to cover a few minutes of peak demand, reducing seasonal efficiency and increasing operating costs.

The integration of i-TES thermal batteries

To meet the peak demand identified during the design phase without resorting to large-scale generators, integrating advanced storage systems becomes the key solution.

i-TES thermal batteries, based on phase change material (PCM) technology, offer a different approach compared to traditional systems:

• Separation between power and draw-off: They allow the calculation of DHW flow rate to be separated from the generator's nominal power.
• Peak management: Thermal storage absorbs peak demand, allowing the generator to operate in a stable, continuous, and efficient manner.
• Compactness and responsiveness: Unlike the large water volumes required by traditional tanks, PCM batteries store latent heat in compact spaces, offering a rapid response exactly where demand is concentrated.

This is precisely the topic explored in the article dedicated to heat pumps and thermal batteries as a quick response to the limitations of using only the generator: the design flow rate creates peaks that should not be handled solely by the production unit.

Conclusion

Properly understanding the UNI EN 806 standard allows for an accurate definition of the system’s operating parameters. Once the design flow rate is determined, adopting latent storage technologies like those of i-TES represents a flexible and consistent solution to ensure service continuity and energy efficiency in modern buildings.