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Subject to change without notice.
83054500bUK – Translation into English of the original German operating manual ait-deutschland GmbH
ON THE SAFE SIDE WITH LOW-SALT OPERATION
The problems listed above do not occur at all with low-salt
operation, as the heating water contains neither corrosive
salts such as sulphates, chlorides and nitrates nor alkalising
sodium hydrogen carbonate. 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 attained 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.
Filling and venting the heating circuit…
Open the additional venting valve at the condenser of
the heat pump. Venting the condenser…
Insulating the hydraulic
connections
Insulate the vibration isolators and the fixed piping of
the heating circuit laid outdoors with vapour-diffusion
impermeable insulation.
Insulate according to the relevant local standards, guidelines
and directives.
ATTENTION
Lay the fixed piping of the heating circuit outdoors
below the frost boundary.
Check that all hydraulic connections are leaktight.
Perform leak test…
Insulate all connection, connectors and pipes of the
heating circuit and the heat source.
LIMESCALE – THE ENERGY KILLER
Filling with untreated drinking water inevitably leads to
the precipitation of all calcium as scale. The consequence:
limescale deposits form on the heat transfer surfaces of
the heating. Efficiency falls and energy costs rise. A rule of
thumb is that 1 millimetre of limescale deposit causes an
efficiency loss of 10 %. In extreme cases it can even cause
damage to the heat exchangers.
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 dis-
solved, corrosive salts which, due to the use of different ma-
terials in the heating system, act as electrolytes and there-
fore accelerate corrosion processes. This can ultimately re-
sult in pitting.
