Heat exchanger operating limits
24.10.2018
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Copyright
2018 by: WATERKOTTE GmbH Subject to changes.
14
Heat exchanger operating limits
When using groundwater as a heat source / domestic water in drinking water installations, the limiting values listed
below (see table and diagram) must be observed according to heat exchangers. The soldered plate heat exchanger
consists of embossed stainless steel plates 1.4401 or AISI 316. You must therefore take the corrosion behaviour of
stainless steel and the solder material, copper or nickel, into account.
Water const value
Unit
Plate heat exchanger,
Copper-soldered (standard)
Plate heat exchanger
Nickel-soldered (standard)
pH value
7 – 9 (allowing for SI index)
6 – 10
Saturation index SI
(∆pH value)
-0.2 < 0 < +0.2
not determined
Overall hardness
°dH
6 – 15
6 – 15
Conductivity
μS/cm
10 ... 500
not determined
Filterable materials
mg/l
< 30
< 30
Chloride (Cl-)
mg/l
see diagram below, no chloride permissible above 100 °C
Free chlorine
mg/l
< 0.5
< 0,5
Hydrogen sulphide (H2S)
mg/l
< 0.05
not determined
Ammonia (NH3 / NH4+)
mg/l
< 2
not determined
Sulphate (SO42-)
mg/l
< 100
< 300
Hydrogen carbonate (HCO3)
mg/l
< 300
not determined
Hydrogen carbonate / sul-
phate
mg/l
> 1
not determined
Sulphite (SO32-)
mg/l
< 1
< 5
Nitrate (NO3-)
mg/l
< 100
not determined
Nitrite (NO2-)
mg/l
< 0.1
not determined
Iron, dissolved (Fe)
mg/l
< 0.2
not determined
Manganese (Mn)
mg/l
< 0.1
not determined
Free aggressive carbon diox-
ide (H2CO3)
mg/l
< 20
not determined
The above values are guide values which can vary under certain conditions.
Figure 5: Permissible chloride content depending on temperature
