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4 Dimensioning and planning
2020/06
99640x5xx-mub-en – V01
11
4.2
Water quality requirements
The domestic hot water modules constructively decrease the precipitation of chalk in the heat
exchanger.
For installations with an elevated total hardness of the potable water and/or high
temperatures, a water treatment is recommended.
The choice of the heat exchanger depends on the requirements of the installation location.
Depending on the chemical composition of the water at the installation site, the adequacy of
the plate heat exchanger has to be checked.
Please observe the following table:
Influence of the water quality on the corrosion resistance for domestic hot water applications
Water content
Concentration
(mg/l or ppm)
Time limits
Heat exchanger
with copper
solder
Coated heat
exchanger
Alkalinity (HCO
3-
)
< 70
within
of
24 hours
0
+
70-300
+
+
> 300
0/+
+
Sulphate (SO
42-
)
< 70
no limit
+
+
70-300
0/-
+
> 300
-
+
HCO
3-
/ SO
42-
> 1.0
no limit
+
+
< 1.0
0/-
+
Electrical
conductivity
< 10 μS/cm
no limit
0
+
10-
500 μS/cm
+
+
>
500 μS/cm
0
+
pH value
< 6.0
within
of
24 hours
0
+
6.0-7.5
0
+
7.5-9.0
+
+
9.0-10
0
0
> 10.0
0
-