Viessmann VITOCROSSAL 300 Service Instructions Manual page 12

Initial start-up, inspection and maintenance
Further details of the individual steps
Diaphragm expansion vessels
1. Drain the system or close the cap
valve on the diaphragm expansion
vessel and reduce the pressure,
until the pressure gauge
indicates "0".
Please note:
The inlet pressure of the
diaphragm expansion vessel (p
comprises the static system
pressure (p ) (= static head)
St
and a supplement
(p = p + supplement).
0 St
The supplement is subject to the
settings of the high limit safety
cut-out.
Depending on the temperature
settings, the following supplements
apply:
H 100 ºC
H 110 ºC
12
)
0
0.2 bar
0.7 bar
(cont.)
2. If the inlet pressure of the
diaphragm expansion vessel is
lower than the value calculated
acc. to the adjacent formula, top
up with sufficient nitrogen to
achieve this value.
3. Re-fill with water until the filling
pressure is 0.2 higher than the
inlet pressure of the diaphragm
expansion vessel when the system
is cold.
4. Mark this value on the pressure
gauge as minimum filling
pressure.