General Recommendations - Ariston VELIS 50 Gebrauchs- Und Montageanweisung

EN
Anti-legionella recommendations (European standard CEN/TR
16355)
Informative
Legionella are small 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 pneu-
mophilia or other Legionella species. This bacterium is frequently found in domestic, hotel and other water
systems and in water used for air conditioning 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 preven-
tion of Legio-nella 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 tem-
perature 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
installation should be used or flushed at least weekly;
• nutrients, biofilm and sediment within the installation including water heaters, etc. Sediment can sup-
port the growth of Legionella bacteria and it should be removed on a regular basis from e.g. storage
systems, water heaters, 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 kept constant in the range 25 - 50°C and the Legionella bacteria could grow in
the tank. In such circumstances, reduce the proliferation of the bacteria by running a "thermal sanitisation
cycle" . Water heaters are sold with software that allows a "thermal sanitisation cycle" to be run when it is
activated in order to reduce the proliferation of Legionella in the tank. This cycle is suitable for domestic
hot water systems and complies with the guidelines for the prevention of Legionella stipulated in Table 2 of
standard CEN/TR 16355 (see below).
Separate hot and cold water
No storage
No
Circulation
circulation
of hot water
of hot water
Ref. in
C.1 C.2
Annex C
Temperature
- ≥ 50 °C
Stagnation
- ≤ 3 l
Sediment
-
a Temperature ≥ 55°C all day or at least 1h a day ≥60°C.
b Volume of water contained in the pipes between the circulation system and the most distant tap.
c Remove the sediment from the storage heater as required by local conditions, but no less frequently than once a year.
d Thermal disinfection for 20 minutes at 60°C, for 10 minutes at 65°C or 5 minutes at 70 °C at all delivery points at least once a week.
e The water temperature in the circulation circuit may not fall below 50°C.
- Not required
Electromechanical water heaters are sold with the thermal sanitisation cycle disabled (default setting). If, for
some reason, any of the above "conditions in favour of the proliferation of Legionella" occurs, it is strongly
recommended to enable this function according to the instructions found in this manual [see <<Activating
the "thermal disinfection cycle" (anti-legionella)>>].
However, the thermal disinfection cycle does not kill all Legionella bacteria in the storage tank. It follows that
if the function is disabled, the Legionella bacteria may reoccur.
Note: when the software performs the thermal sanitisation treatment, it is likely that the power consumption
of the water heaters increases.
20
Table 2 - Types of hot water system
Storage
No
Circulation
circulation
of mixed
of mixed
water
water
C.3 C.4
in
storage ≥ 50 °C disinfection
e e
heater
a
- ≤ 3 l
b b
remove remove
- c c
Mixed hot and cold water
No storage upline Storage upline
of the mixer of the mixer
valves
No
No
Circulation
circulation
circulation
of mixed
of mixed
of mixed
water
water
water
C.5 C.6 C.7
thermal thermal in
disinfection storage
d d
heater
- ≤ 3 l -
b
- - remove
No storage upline
of the mixer
valves valves
No
Circulation
Circulation
circulation
of mixed
of mixed
water
water
C.8 C.9
≥ 50 °C
e
thermal thermal
thermal
disinfection disinfection
d
disinfection d
a
≤ 3 l -
b
remove
c c -
of mixed
water
C.10
d
≤ 3 l
b
-