Viessmann Vitomax HS M73 Operating And Service Instructions page 16

Shutdown and preservation
Shutdown
(cont.)
Interruption in operation
Treatment for preservation of the water side
Dry preservation
Note
Restarting the system quickly is not possible.
Applications:
■ Prolonged boiler idle periods
■ Risk of frost *1
1. Drain the steam boiler.
!
Please note
Draining hot water into the sewage system
causes environmental damage.
Therefore cool the water to < 35 °C before-
hand. If necessary, collect it in containers.
2. Flush the steam boiler again on the water side,
using high salt content flushing water
( 5000 S/cm).
> µ
3. Open the water closures.
Note
Components such as ECO must be dried out sepa-
rately.
4. Dry the boiler system thoroughly.
5. Place desiccant (silica gel) in the boiler system in
accordance with the manufacturer's instructions.
Note
Ensure that the desiccant does not come into
direct contact with the boiler material.
6. Close the boiler system.
7. Check the effectiveness of the desiccant regularly.
Wet preservation
1. Fill the boiler system (incl. ECO, if installed) up to
the highest possible level with treated feedwater.
See the "Using antifreeze in boilers" chapter in the technical guide
*1
16
3 days
>
2. Note
To prevent oxygen corrosion, mix oxygen binder,
e.g. sodium sulphite, into the boiler water in
accordance with the manufacturer's instructions.
Mix the oxygen binder thoroughly with the boiler
water by means of thermal or mechanical circula-
tion.
3. Check the concentration of the oxygen binder at
regular intervals and at least every month. If nec-
essary, add more oxygen binder.
Preservation with sodium sulphite
1. Add the sodium sulphite in soluble form to the
completely drained steam boiler via the feedwater
pump.
Note
When carrying out the preservation, keep all
valves/fittings closed.
2. Fill the steam boiler completely. Also fill the ECO (if
installed).
3. Set pH value to between 11 and 12.
4. Circulate preservation solution weekly.
5. Circulation
Initially, check the sulphide excess frequently, then
at least monthly. If the concentration falls below the
specified standard values, recirculate and top up if
necessary.
6. For unvented, cold treated water: Add an additional
80 g desiccated or 160 g crystallised sodium sul-
phite per 1 m 3 .