Wolf FWS-2-80, Installation Instructions Manual, Page: 43 / 104

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To protect against scaling, the DHW temperature should be set to max. 50 °C if the
total water hardness is 15 °dH (2.5 mol/m³) or above.
In accordance with the Drinking Water Ordinance [Germany], this is the lowest
permissible value for DHW temperatures, given that it practically rules out the risk of
legionella proliferation with daily use of the hot water system. With a total hardness
of 20 °dH or higher, the use of a water treatment facility in the cold water supply line
when heating DHW is necessary in order to extend the maintenance intervals. Even if
water hardness is below 20 °dH, a higher risk of scaling may occur locally, necessita-
ting suitable softening measures. Failure to take such measures will result in prema-
ture scaling of the appliance and a reduction in the convenient availability of domestic
hot water. The contractor responsible should always check the local conditions.
Protection against scaling
Water limit values
Maintenance
Limits
pH value (taking account of the saturation index SI) 7-9
Saturation index SI (delta pH value) -0.2 < 0 < 0.2
Total hardness [°dH] 6-15
Conductivity [µS/cm] 10...600
Substances that can be filtered out [mg/l] < 30
Free chlorine [mg/l] < 0.5
Hydrogen sulphide (H2S) [mg/l] < 0.05
Ammonia (NH3/NH4+) [mg/l] < 2
Sulphate [mg/l] < 100
Hydrogen carbonate [mg/l] < 300
Hydrogen carbonate / sulphate [mg/l] > 1.0
Sulphide [mg/l] < 1
Nitrate [mg/l] < 0.1
Iron, dissolved [mg/l] < 0.2
Manganese [mg/l] < 0.1
Free aggressive carbonic acid [mg/l] < 20