Ariston C00520 Mode D'emploi page 17

Anti-legionella recommendations (European standard CEN/TR 16355)
Information
Legionella is a small bacterium, of stick-like form, and is found naturally in fresh water.
Legionnaire's disease is a serious pulmonary infection caused by inhalation of the Legionella pneumophilia bacterium
and other species of Legionella . The bacterium is frequently to be found in the plumbing of houses, hotels and water
used in A/C and air cooling systems. The most effective measure against infection is to prevent the bacterium proliferating
in water circuits.
European standard CEN/TR 16355 provides guidelines for preventing the proliferation of Legionella in drinking water
systems, without substituting applicable local legislation.
General recommendations
"Conditions favourable to the proliferation of Legionella". The following conditions are favourable to the proliferation
of Legionella:
Water temperature in the range 25 - 50 °C. To reduce the proliferation of Legionella, the water temperature be
•
kept with these limits to prevent them growing or reduce their growth to a minimum. If this is not possible, the
drinking water system must be sanitised thermally;
• Stagnant water. To prevent water stagnating for a long time, the drinking water system must be flushed or made
to run abundantly at least once a week;
• Nutrients, biofilms and sediment in the circuit, including boilers, etc. Sediment may promote the proliferation of
Legionella and should be regularly eliminated from water storage devices, boilers and expansion/holding tanks
(for instance, once a year).
As regards storage heater like the present, if:
1) the appliance is switched off for several months at a time 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.1 C.2 C.2 C.2
Enclosure C
≥ 50 °C
Temperature - -
≤ 3 l
Stagnation - -
- -
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
Table 2 - Types of hot water system
Storage
No
Circulation
circulation
of mixed
of mixed
water
water
C.3 C.4 C.4
≥ 50 °C
e e
in
storage disinfection
a
heater
≤ 3 l
b b
-
c c
- - - remove remove
Mixed hot and cold water
No storage Storage upline
upline of the of the mixer
mixer valves valves
No No
Circulation
circulation circulation
of mixed
of mixed of mixed
water
water water
C.5 C.5 C.6 C.6 C.6 C.7 C.7
thermal thermal in
d d
disinfection storage
heater
≤ 3 l
b
- - - -
- - - - - remove
No storage
upline of the
mixer valves
No
Circulation Circulation
circulation
of mixed of mixed
of mixed
water water
water
C.8 C.9 C.9 C.10
≥ 50 °C
e
thermal thermal
d
thermal
disinfection disinfection
d
a
disinfection
≤ 3 l ≤ 3 l
b
- -
c c
remove - -
EN
d
b
-
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