Viessmann VITOCROSSAL 300 Service Instructions Manual page 24

Water quality requirements
■ In systems > 50 kW, install a water
meter to capture the amount of the fill
and top-up water. Enter the volume of
the fill water and the water hardness
into the boiler maintenance checklists.
■ For systems with a specific system vol-
ume in excess of 20 l/kW heating out-
put (apply the output of the smallest
boiler in multi boiler systems), apply
the requirements of the next highest
category of total output (in accordance
with the table). In the case of severe
excess (> 50 l/kW) soften down to a
total amount of alkaline earths ≤
3
0.02 mol/m .
Operating information:
■ During extension or repair work, only
drain the necessary pipework sec-
tions.
■ Check, clean and activate filters, dirt
traps and other blow-down or separat-
ing facilities in the heating water circuit
more frequently after commissioning
or new installations; later on do so sub-
ject to requirements in line with the
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 filled, not with
fully softened water, but with water
that meets the requirements in the
above table, also observe the follow-
ing during commissioning:
24
(cont.)
■ Commission the system step by step,
starting with the lowest boiler output
and a high heating water flow rate.
This prevents a localised concentra-
tion of limescale deposits on the boiler
heating surfaces.
■ In multi boiler systems, start all boilers
simultaneously to prevent the entire
limescale deposit settling in the heat
transfer area 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. after repairs or after system
expansion, and for all amounts of top-
up water.
The build-up of limescale deposits on the
heating surfaces will be minimised if
these instructions are observed.
Any limescale deposits that have formed
because of a failure to observe the
requirements to VDI Directive 2035 will
in most cases already have caused a
reduction in the service life of the instal-
led heating equipment. Removing the
limescale deposits is one option for
restoring operational viability.
This measure must be carried out by a
specialist. Inspect the heating system for
possible damage prior to returning it into
use. It is essential that the faulty operat-
ing parameters are corrected to prevent
renewed formation of excessive scale
deposits.