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Water quality requirements
Water quality requirements
The pre-charge pressure of the dia-
phragm expansion vessel should be
checked at least during the annual serv-
ice.
The use of permeable components, e.g.
plastic pipes that are permeable to gas
in underfloor heating systems, should be
avoided. Provide system separation if
such components are nevertheless
used. This must separate the water flow-
ing through the plastic pipes from other
heating circuits, e.g. from the boiler, by
the provision of a corrosion resistant
heat exchanger.
No further anti-corrosion measures are
required for sealed hot water heating
systems subject to the above points
being observed.
However, take additional precautions
where there is a risk of oxygen ingress,
for example by adding oxygen binder
sodium sulphite (5 - 10 mg/litre into the
excess). The heating water should have
a pH value between 9.0 and 10.5.
Using antifreeze in boilers
Viessmann boilers are designed and
built for water as a heat transfer medium.
To protect boiler systems from frost, it
may be necessary to treat the boiler or
circuit water with antifreeze.
When doing so, observe the following:
■ As a general principle, follow the spec-
ifications given by the antifreeze man-
ufacturer.
■ The properties of antifreeze and water
are very different.
24
(cont.)
Different conditions apply to systems
that contain aluminium components.
Where chemicals are used as part of the
corrosion protection, we recommend
that the manufacturer of the chemicals
issues a certificate of suitability of the
additives with regard to the boiler mate-
rials and the materials of the other heat-
ing system components.
We recommend you refer questions of
water treatment to Viessmann industrial
services or an appropriate specialist.
Further details can be found in VDI
Directive 2035-2 and EN 14868.
■ The temperature stability of the anti-
freeze must be sufficient for the par-
ticular application.
■ Check the compatibility with sealing
materials. If other sealing materials
are used, take this into account when
designing the system.
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