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2. Legionella prevention
Recommendations based on European standard CEN/TR 16355
Legionella are rod shaped bacteria which are a natural constituent of all fresh waters.
Legionaries' disease is a serious pneumonia infection caused by inhaling the bacteria Legionella pneumophilia or other
Legionella species. This bacterium can be found in domestic, hotel and other water systems and in water used for air condi-
tioning or air cooling system. Hence the main intervention against the condition is prevention, through control of the organism
in water systems.
The European standard CEN/TR 16355 gives recommendations for good practice concerning the prevention of Legionella
growth in drinking water installations but existing national regulations remain in force.
General recommendations
"Conditions for Legionella growth". The following conditions encourage Legionella growth:
• water temperature between 25 °C and 50 °C. To restrict the growth of Legionella bacteria, the water temperature
shall be in a range that the bacteria will not grow or have minimum growth, wherever possible. Otherwise, it is
necessary to disinfect a drinking water installation by means of a thermal treatment;
• stagnation of the water. To avoid long periods of stagnation, the water in every part of the drinking water installa-
tion should be used or flushed at least weekly;
• nutrients, biofilm and sediment within the installation including water heaters, etc. Sediment can support the
growth of Legionella bacteria and it should be removed on a regular basis from e.g. storage systems, water heat-
ers, non-flown through expansion vessels (e.g. once a year).
Regarding to this storage water heater, if...
1. the product is switched-off for a period of time [months] or
2. the water temperature is permanently maintained between 25 °C and 50 °C,
the Legionella bacteria could growth inside the tank. In these cases, to restrict the Legionella growth, it is necessary to
perform the so called "thermal disinfection cycle".
This electro-mechanical storage water heater is equipped with a thermostat setable at a temperature higher than
60 °C; it means it is enabled to carry out a "thermal disinfection cycle" to restrict the Legionella growth inside the tank.
This cycle complies with the hot water installations and relevant recommendations for Legionella prevention specified
in the following Table of the CEN/TR 16355.
Types of hot water installation
Hot and cold water separately
No storage
No circula-
tion of hot
water
Ref. in
C.1
Annex C
Temperature
-
Stagnation
-
Sediment
-
a
Temperature ≥ 55 °C the whole day or at least 1 h per day ≥ 60 °C.
b
The volume of water contained in the pipework between the circulation system and the tap which has the greatest distance to the system.
c
Remove the sediment from the storage water heater in accordance with the local conditions but at least once a year.
d
Thermal disinfection for 20 min at a temperature of 60 °C, for 10 min at 65 °C or for 5 min at 70 °C at every draw-off point at least once a week.
e
The water in the circulation loop shall not be less than 50 °C.
-
No requirement.
www.clage-com.ru
Storage
No cir-
With cir-
Circulation
culation
culation of
of mixed
of mixed
hot water
water
water
C.2
C.3
C.4
≥ 50 °C
in the stor-
≥ 50 °C
e
age water
heater
a
≤ 3 l
-
≤ 3 l
b
-
remove
remove
c
Mixed hot and cold water
No storage upstream
of mixing valves
No cir-
Circulation
culation
of mixed
of mixed
water
water
C.5
C.6
thermal
thermal
in the stor-
e
disinfec-
disinfec-
age water
tion
tion
d
d
-
≤ 3 l
b
b
-
-
c
18
Storage upstream of
No storage upstream
mixing valves
of mixing valves
No cir-
No cir-
Circulation
culation
culation
of mixed
of mixed
of mixed
water
water
water
C.7
C.8
C.9
≥ 50 °C
thermal
e
thermal dis-
disinfec-
heater
infection
tion
a
d
-
≤ 3 l
-
b
remove
remove
-
c
c
With
circulation
of mixed
water
C.10
thermal
disinfec-
tion
d
d
≤ 3 l
b
-
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