Important
A softening system reduces calcium and magnesium to prevent
the formation of scale (VDI directive 2035 Sheet 1). No corrosive
water components are reduced or removed (VDI directive 2035
Sheet 2).
Tab.6
Table to VDI 2035 Sheet 1
Total heating output in kW
Total hardness in °dH depending on the specific system volume
< 20 l/kW
≤ 20 l/kW and < 50 l/kW
≥ 50 l/kW
≤ 16.8
≤ 11.2
< 0.11
50 - 200
≤ 11.2
≤ 8.4
< 0.11
200 - 600
≤ 8.4
< 0.11
< 0.11
> 600
< 0.11
< 0.11
< 0.11
(1) for circulation water heaters (< 0.3 l/kW) and systems with electric heating elements
5.5.3
Full desalination/partial desalination
Use of a desalination system to treat the fill water.
Fully desalinated water or partially desalinated water can generally be
used for filling.
The electrical conductivity of desalinated additional water must not
exceed 15 μs/cm for full desalination and 180 μs/cm for partial
desalination.
The electrical conductivity in the circuit must not exceed 50 μS/cm with
full desalination and 370 μS/cm with partial desalination during filling.
The pH of the circuit water must be between 8.2 and 9.0 during
operation.
The pH, electrical conductivity and product content of the heating water
must be checked after eight weeks of operation and then once per year.
Desalination of fill and top-up water to obtain fully desalinated water
should not be mistaken for softening down to 0 °dH. Water softening
does not remove corrosive salts.
5 Before installation
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