This dynamic balancing valve is manufactured in stainless steel in order to ensure the highest possible resistance against corrosion in domestic hot water, but it is based on familiar and extremely well-proven technology.
It is, in fact, identical to one of Frese’s classic valves - The Frese ALPHA - which has been used in heating and cooling systems all over the world for several years. Only the material is different - the core features and benefits remain exactly the same.
The dynamic properties of Frese ALPHA Sanitary ensure balance throughout the circulation system, regardless of fluctuating pressure conditions and water temperature. Once the valve has been installed with the correct cartridge for the system in question, you will at all times achieve the exact flow required to compensate for heat loss in the pipes.
This way there will always be quick access to hot water even at outlying tapping points, so consumers will not be left waiting.
Flow control is particularly relevant since many district heating providers are attempting to run their distribution systems at lower temperatures. This may pose a challenge for thermostatic circulation control, while Frese ALPHA Sanitary is in no way affected by this development.
Because Frese ALPHA Sanitary performs its balancing tasks with no regard for water temperature, this valve is ideal for thermal disinfection in domestic hot water systems, since this process can be accomplished with no disruption of normal operation.
More than 90% of cases of Legionnaires’ disease are caused by Legionella pneumophila.
Most other types of Legionella bacteria behave similarly to Legionella pneumophila regarding thermal disinfection.
Legionella bacteria grow readily at temperatures in the range 20°C to 50°C.
Legionella bacteria in concentrations of 100,000 colony forming units per litre (cfu/l) and higher are not uncommon at the base of conventional hot water storage vessels where temperatures of 20°C to 50°C are maintained.
Under optimum conditions, Legionella bacteria can multiply from background numbers to dangerous concentrations in less than five days.
The effectiveness of inactivating Legionella bacteria using raised temperatures (thermal disinfection) depends upon the temperature and how long the bacteria are exposed to that temperature.
Thermal inactivation of Legionella bacteria starts around 45-50°C but is quicker at higher temperatures.
Legionella pneumophila requires on average 2 minutes exposure to 60°C to inactivate 90% of the bacteria.
Where the water contains 100,000 cfu/l Legionella, the bacteria need to be held at 60°C for approximately 10 minutes to reduce numbers to below the action level of 1000 cfu/l.
Hot water storage cylinders that maintain a temperature of 60°C throughout the whole storage vessel for a period of one hour daily should achieve satisfactory control of Legionella bacteria, in line with health authority recommendations. Rules and threshold values vary between European countries.
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