Viessmann Vitocrossal 300 Service Instructions For Contractors page 140

Water quality requirements
■ In systems > 50 kW, install a water
meter to capture the volume of the fill
& top-up water. Enter the amount of fill
water and the water hardness into the
boiler service check lists.
■ For systems with a specific system vol-
ume in excess of 20 l/kW output (apply
the output of the smallest boiler in multi
boiler systems), apply the require-
ments of the next highest category of
total output (in accordance with the
table). In the case of severe excess
(> 50 l/kW), soften the water down to
a total of alkaline earths of ≤
0.02 mol/m 3 .
Operating information:
■ During expansion or repair work, only
drain the necessary pipework sec-
tions.
■ Filters, dirt traps and other blow-down
or separating facilities in the heating
water circuit must be checked,
cleaned and activated more frequently
after commissioning or recommission-
ing, and later on as required, subject
to 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:
140
(cont.)
■ Commission the system step by step,
starting with the lowest boiler output
and at 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
lime deposit settling in the heat trans-
fer area of just one boiler.
■ Where water treatment is required,
treat even the first fill of the heating
systems prior to commissioning. This
also applies to any subsequent filling,
e.g. when adding top-up water, after a
repair or after system expansion.
The build-up of limescale deposits on the
heating surfaces will be minimised if
these instructions are observed.
Any scale deposits that have formed
because the requirements to VDI Direc-
tive 2035 have not been observed, will in
most cases already have caused a
reduction in the service life of the instal-
led heating appliance. 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.