Using Antifreeze In Boilers - Viessmann VITOPLEX 100 Service Instructions Manual

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
water or circulating water with anti-
freeze.
When doing so, observe the following:
■ In general, follow the specifications
given by the antifreeze manufacturer.
■ The properties of antifreeze and water
are very different.
■ 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.
■ Antifreeze developed especially for
heating systems contains inhibitors
and buffer substances for corrosion
protection as well as glycol. When
using antifreeze, always observe the
manufacturer's instructions regarding
minimum and maximum concentra-
tions.
■ The concentration must never fall
below the prescribed minimum level,
subject to the required frost protection
temperature. Check and adjust the pH
value and frost protection (measure
the density) regularly, at least once a
year, according to the manufacturer's
instructions.
■ Check with the relevant supplier
whether antifreeze may affect system
components that are not part of the
boiler, such as pumps, electrically and
pneumatically driven valves, other
types of valves, gaskets, etc.
■ If the system is filled with antifreeze, it
must be marked accordingly.
■ If a boiler system is changed to oper-
ate without antifreeze, flush the sys-
tem in order to remove all traces of the
antifreeze.
■ The quality of the boiler water and
feedwater must meet the require-
ments of Directive VDI 2035.
■ The systems must be designed as
sealed unvented systems, as the anti-
freeze inhibitors decrease rapidly if air-
borne oxygen is allowed to enter.
■ Diaphragm expansion vessels must
comply with DIN 4807 [or local regula-
tions].
■ Solder connections should preferably
be made with Ag or Cu hard solder. If
liquids containing chlorides are used
for soft soldering, any deposits must
be removed from the circuit afterwards
through thorough flushing. A higher
chloride content in the heat transfer
medium can cause corrosion damage.
■ Only use oxygen diffusion-resistant
hoses or metal hoses for flexible con-
nections.
■ Never equip the system on the primary
side with zinc-plated heat exchangers,
containers or pipes as zinc can be cor-
roded by glycol/water mixtures.
■ To avoid the risk of corrosion, ensure
that there is no difference in electrical
potential between system compo-
nents that are in contact with anti-
freeze.
■ Route all pipes in such a way that cir-
culation cannot be interrupted by gas
cushions or deposits.
■ The water circuit must always be filled
up to the highest point with the heat
transfer medium.
Water quality
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