Viessmann Vitomax 200-HW Operating And Service Instructions page 7

Shutdown
(cont.)
Longer interruptions of operation
Water side
Wet conservation, as long as there is no risk of frost
1. Fill the boiler up to the highest pos-
sible level with treated feedwater.
To prevent oxygen corrosion, add
an oxygen binder to the boiler water
(e.g. sodium sulphite) in accor-
dance with the manufacturer's
instructions. For this, ensure good
admixing with the boiler water
(thermal or mechanical agitation).
2. If, in multi-boiler systems, only
some boilers must be conserved,
these can be filled with desalinated
boiler water from the boilers that
remain in use, which will also main-
tain the temperature.
3. Maintaining pressure in a fully filled
boiler using nitrogen (preferably
nitrogen 5.0) of 0.1 to 0.2 bar can
prevent corrosion.
Dry conservation in case there is a risk of frost or in case of longer idle
periods
Drain the boiler at a temperature
between 120 and 140 °C, then open
the fittings on the water side.
Dry the boiler thoroughly and fill with
desiccant (e.g. silica gel) in accor-
dance with the manufacturer's details.
Flue gas side
Thoroughly clean and dry the sur-
faces on the flue gas side.
Maintain the alkaline balance of the
wash water (pH 8-9, in case of ammo-
nia pH 10).
Operating information
Ensure that the desiccant does not
come into contact with the boiler
material. Then close the boiler again.
Check in regular intervals whether the
desiccant is still able to absorb moist-
ure.
After the surfaces have been dried
completely, conserve them with a thin
film of graphite or boiled oil.
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