Water Quality Requirements - Viessmann VITOCROSSAL Service Instructions Manual

Water quality
Requirements

Water quality requirements

Note
Observing the following requirements is necessary to
safeguard your warranty rights.
The warranty excludes damage due to corrosion and
scaling.
Total heating output
kW
50
≤
50 to 200
> ≤
200 to 600
> ≤
600
>
The standard values assume the following:
■ The total 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
■
heating output. In multi boiler systems, apply the out-
put of the smallest boiler.
■ All measures to prevent corrosion on the water side
in accordance with VDI 2035 Part 2 have been
implemented.
Soften the fill and top-up water in heating systems
operating under the following conditions:
■ The total of alkaline earths in the fill and top-up water
exceeds the standard value.
■ Higher fill and top-up water volumes are expected.
■ The specific system volume is greater than 20 l/kW
heating output. In multi boiler systems, apply the out-
put of the smallest boiler.
■ In systems > 50 kW, install a water meter to capture
the amount of fill and top-up water. Enter the volume
of fill water and the water hardness into the boiler
maintenance checklists.
For systems with a specific system volume greater
■
than 20 l/kW heating output, apply the requirements
of the next higher category of total heating output (in
accordance with the table). In multi boiler systems,
apply the output of the smallest boiler. In the case of
severe overshoot (> 50 l/kW), soften the water down
to a total of alkaline earths of
102
Total alkaline earths
mol/m 3
3.0
≤
2.0
≤
1.5
≤
< 0.02
0.02 mol/m 3 .
≤
Prevention of damage due to scaling
Prevent excessive scale build-up (calcium carbonate)
on the heating surfaces. For heating systems with
operating temperatures up to 100 °C, VDI Guideline
2035 Part 1 "Prevention of damage in water heating
installations - Scale formation in domestic hot water
supply installations and water heating installations"
applies together with the following standard values.
See the explanations in the original text of the Guide-
line.
Operating information:
■ During expansion or repair work, only drain the pipe-
work sections necessary.
■ Check, clean and activate filters, dirt traps and other
blow-down or separating facilities in the heating
water circuit frequently after commissioning and in
new installations. Thereafter check and maintain
these facilities as required, depending on the type of
water treatment applied (e.g. water softening).
■ No further steps are required during commissioning
if you fill the heating system with fully softened
water.
If the heating system is charged, not with fully soft-
ened water, but with water that meets the require-
ments in the above table, also observe the follow-
ing during commissioning:
■ Commission the system step by step with a high
heating water flow rate, starting with the lowest boiler
output. This prevents localised concentration of lime-
scale deposits on the boiler heating surfaces.
■ In multi boiler systems, start all boilers simultane-
ously to prevent the entire limescale deposit settling
in the heat exchanger of just one boiler.
■ Where water treatment is required, treat even the
first fill of the heating system prior to commissioning.
This also applies to any subsequent filling, e.g. when
adding top-up water or after a repair, or for any sys-
tem expansion.
The build-up of limescale deposits on the heating sur-
faces will be minimised if these instructions are fol-
lowed.
Failure to observe the requirements of VDI Guideline
2035 can result in damaging limescale deposits. In
such cases, the service life of the installed boilers will,
most often, already have been reduced. Removing the
limescale deposits is one option for restoring opera-
tional viability.
Total hardness
dH
°
16.8
≤
11.2
≤
8.4
≤
< 0.11