Viessmann VITOCROSSAL 300 Service Instructions Manual page 30

Specification
Water quality requirements
Prevention of damage due to scaling
Excessive scale deposits (calcium carbonate) on the heating surfaces should
be prevented. For heating systems with operating temperatures up to 100 °C,
the VDI Directive 2035 sheet 1 "Prevention of heating system damage – scaling
in DHW and hot water heating systems" applies [in Germany] together with the
following standard values (see also the full explanations in the original Direc-
tive).
Total output
kW
> 50 to ≤ 200
> 200 to ≤ 600
> 600
The standard values assume the fol-
lowing:
& The volume of fill and top-up water
will not exceed three times the
water content of the heating system
during its service life.
& The specific system volume is less
than 20 l/kW output. In multi-boiler
systems, apply the output of the
smallest boiler.
& All measures to prevent corrosion
on the water side in accordance
with VDI 2035 Sheet 2 have been
implemented.
Soften the fill & top-up water in heat-
ing systems operating under the fol-
lowing conditions:
& The total of alkaline earths in the fill
& top-up water exceed the standard
value.
& Higher fill & top-up water volumes
are expected.
& The specific system volume is less
than 20 l/kW output. In multi-boiler
systems, apply the output of the
smallest boiler.
30
(cont.)
Total of alkaline earths
3
mol/m
≤ 2.0
≤ 1.5
< 0.02
& In systems > 50 kW, install a water
meter to record the volume of the fill
& top-up water. Enter the volume of
water and the water hardness into
the boiler service checklists.
& For systems with a specific system
volume in excess of 20 l/kW output
(apply the output of the smallest
boiler in multi-boiler systems), apply
the requirements of the next higher
category of total output (in accor-
dance with the table). In case of
severe excess (> 50 l/kW), soften
the water down to a total of alkaline
earths ≤ 0.02 mol/m
Total hardness
°dH
≤ 11.2
≤ 8.4
< 0.11
3
.