Ariston VLS EVO INOX 80 PW O 3700632 - Инструкция по эксплуатации - Страница 52

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 pneumophilia 

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 prevention 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 tempera-

ture shall be in a range that the bacteria will not grow or have minimum growth, wherever possible. Other-

wise, 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 support 

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). 

Table 2 - Types of hot water system  

Separate hot and cold water

Mixed hot and cold water

No storage

Storage

No storage upline 

of the mixer valves

Storage upline of 

the mixer

valves

No storage upline 

of the mixer valves

No 

circulation 

of hot 

water

Circulation 

of hot 

water

No

circulation

of mixed 

water

Circulation 

of mixed 

water

No 

circulation

of mixed 

water

Circulation 

of mixed 

water

No

circulation 

of mixed 

water

Circulation

of mixed 

water

No 

circulation

of mixed 

water

Circulation

of mixed 

water

Ref. in

Annex C

C.1

C.2

C.3

C.4

C.5

C.6

C.7

C.8

C.9

C.10

Temperature

-

≥ 50 °C 

e

in

storage 

heater

a

≥ 50 °C 

e

thermal

disinfec-

tion

d

thermal

disinfec-

tion

d

in

storage 

heater

a

≥ 50 °C 

e

thermal

disinfec-

tion

d

thermal

disinfection

d

thermal

disinfec-

tion

d

Stagnation

-

≤ 3 l 

b

-

≤ 3 l 

b

-

≤ 3 l 

b

-

≤ 3 l 

b

-

≤ 3 l 

b

Sediment

-

-

remove

c

remove

c

-

-

remove

c

remove

c

-

-

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 rec-

ommended 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. 

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