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Subject to change without notice.
83054800bUK – Translation into English of the original German operating manual ait-deutschland GmbH
WATER SOFTENING TO VDI 2035 – PART I
If the water is softened in accordance with the VDI 2035
guidelines before it is used to fill the heating system, no scale
can form. This prevents limescale deposits and the resulting
negative effects on the entire heating system, effectively and
permanently.
CORROSION – AN UNDERESTIMATED PROBLEM
VDI 2035, Part II, deals with the problem of corrosion.
Softening the heating water can prove to be insufficient.
The pH value can significantly exceed the limit of 10. pH
values higher than 11 can set in, which even damage rubber
seals. VDI 2035, Part 1 guidelines are nevertheless fulfilled;
however, VDI 2035, Part 2 proposes a pH value between 8.2
and maximum 10.
If aluminium materials are used, which is the case in many
modern heating systems, a pH value of 8.5 must not be
exceeded! Because otherwise there is a threat of corrosion
– aluminium is attacked without the presence of oxygen.
Therefore, in addition to softening the heating fill and make-
up water, the heating water should also be conditioned
appropriately. This is the only way to comply with the
VDI 2035 requirements and the recommendations and
installation instructions of the heat pump manufacturer.
Part 2 of VDI 2035 also refers to the reduction in total salt
content (conductivity). The risk of corrosion is far lower if
deionised water is used than is the case if the system is
operated with salty, i.e. softened water.
Even drinking water softened beforehand contains dissolved,
corrosive salts which, due to the use of different materials
in the heating system, act as electrolytes and therefore
accelerate corrosion processes. This can ultimately result in
pitting.
ON THE SAFE SIDE WITH LOW-SALT OPERATION
With low-salt operation the problems listed above do not
occur at all, as neither corrosive salts such as sulphates,
chlorides and nitrates, nor the alkaline sodium hydrogen
carbonate are present in the heating water. The corrosive
properties of deionised water are very low and in addition,
scale cannot form. This is the ideal approach for closed
heating circuits, in particular, because low oxygen input into
the heating circuit can also be tolerated.
In general, when the system is filled with deionised water,
the pH value sets itself within the ideal range due to “self-
alkalinisation”. If necessary, a pH value of 8.2 can be very
easily alkalised by adding chemicals. In this way, optimum
protection of the entire heating system is achieved.
MONITORING
Analytical recording and monitoring of the relevant water
values and the added conditioning substances is of decisive
importance. Therefore, they should be monitored regularly
using appropriate water test equipment.
FLUSH, FILL AND VENT THE HEATING CIRCUIT AND HOT
WATER TANK
In order to vent the hot water tank the heating circuit and
the hot water supply circuit must be flushed at the same
time.
Flushing, filling and venting the heating circuit…
Venting the additional condenser of the heat pump…
•
Opening the lower facing panel…
•
Opening the vent valve…
After venting, close the lower facing panel.
