Viessmann VITODENS 050-W Technical Manual page 49

Design information
Attic heating centre
The installation of a low water indicator, compulsory according to the
DVGW [Germany], is not required when installing boilers in an attic
heating centre.
The boilers are protected against water shortage in accordance with
EN 12828.
Safety valve
A safety valve in accordance with TRD 721 is integrated in the Vito-
dens (opening pressure 3 bar (0.3 MPa)).
Route the discharge pipe in accordance with EN 12828 into a drain
outlet (drain outlet kit available as an accessory). The drain outlet
incorporates a siphon as a stench trap.
Low water indicator
According to EN 12828, a low water indicator can be omitted for boil-
ers up to 300 kW, as long as heating can be reliably prevented when
there is a water shortage.
Viessmann condensing boilers are equipped with a low water indica-
tor (boil-dry protection). Tests have verified that the burner will be
automatically switched off in the event of water shortage due to a
leak in the heating system and simultaneous burner operation,
before the boiler or the flue system reaches unacceptably high tem-
peratures.
Water quality/frost protection
Fill and top-up water
The quality of the fill and top-up water is one of the key factors for
preventing damage caused by deposits or corrosion in the heating
system.
In order to prevent system damage, the European standards and
national guidelines for fill and top-up water must be observed right
from the design stage, e.g. VDI 2035.
■ Regular checks of the appearance, water hardness, conductivity
and pH value of the heating water during operation lead to higher
operational reliability and system efficiency. These properties must
also be observed for the top-up water. According to VDI 2035, the
quantity and properties of the top-up water must always be docu-
mented in the system log or maintenance reports.
■ The basis for filling the heating system is tap water of potable
water quality in line with Directive 98/83/EC and/or
(EU) 2020/2184. For use as heating water, it is normally sufficient
to soften the tap water. VDI 2035 specifies the maximum recom-
mended concentrations of alkaline earths (hardeners), depending
on the heating output and the specific system volume (ratio of the
heating output of the heat generators to the heating water volume
of the system): See the table below.
Total permissible hardness of the fill and top-up water according to VDI 2035
Total heating output of heat
generator
≤ 50 kW
> 50 to ≤ 200 kW
> 200 to ≤ 600 kW
> 600 kW
*6 In the case of systems with several heat generators that have several different specific water capacities, the smallest specific water ca-
pacity is definitive.
*7 To calculate the specific system volume, the smallest individual heating output should be used for systems with several heat generators.
VITODENS
(cont.)
Specific water capacity of heat
*6
generator
≥ 0.3 l/kW
< 0.3 l/kW
—
—
—
■ We recommend always softening the fill and top-up water, as the
water hardness can vary due to the mixture of different sources of
supply, and the information provided by water supply utilities only
gives average values. The information provided by water supply
utilities is not sufficient for designing the system. In addition, it
must be taken into account that the quantity of top-up water that
will be added to the system during its service life cannot be predic-
ted precisely at the design stage (especially in the case of existing
heating circuits).
■ If no aluminium or aluminium alloy components are installed, the
heating water in systems with Viessmann heat generators does
not need to be fully desalinated.
■ The use of glycol as antifreeze without adequate inhibition and
buffering is not permitted. The suitability of an antifreeze or other
chemical additive should be certified by the manufacturer. Chemi-
cal additives in the heating water require more extensive monitor-
ing and maintenance. Observe the manufacturer's instructions.
Viessmann accepts no liability for damage or operational failure
arising due to the use of unsuitable additives, incorrect dosing or
poor maintenance.
■ Chemical water treatments may only be planned and carried out
by appropriately qualified specialist companies.
*7
Specific system volume
≤ 20 l/kW > 20 to ≤ 40 l/kW
None
3
≤ 3.0 mol/m ≤ 1.5 mol/m
(16.8 °dH)
≤ 2.0 mol/m 3 ≤ 1.0 mol/m
(11.2 °dH)
≤ 1.5 mol/m 3
(8.4 °dH)
3
≤ 0.05 mol/m
(0.3 °dH)
> 40 l/kW
3
≤ 3.0 mol/m ≤ 0.05 mol/m
(16.8 °dH) (0.3 °dH)
3
(8.4 °dH) ≤ 0.05 mol/m
(0.3 °dH)
3 (5.6 °dH) ≤ 0.05 mol/m
(0.3 °dH)
≤ 0.05 mol/m 3 ≤ 0.05 mol/m
(0.3 °dH) (0.3 °dH)
3
≤ 0.05 mol/m ≤ 0.05 mol/m
(0.3 °dH) (0.3 °dH)
VIESMANN
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3
3
3
3
3
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