Cleaning The Light Barriers And Sight Glasses; Checking The Expansion Vessel And System Pressure - Viessmann Vitoligno 300-H Installation And Service Instructions For Contractors

Cleaning the light barriers and sight glasses

Fig. 67
1. Undo the sight glass cover and the top of the sight
glass.
Clean the sight glass.
2. Replace the top of the sight glass and the sight
glass cover.
3. Repeat on the opposite side of the boiler.

Checking the expansion vessel and system pressure

Note
The expansion vessel can lose some of its charge
pressure over time. When the boiler heats up, the
pressure rises to 2 or 3 bar (0.2 or 0.3 MPa). The
safety valve may also respond and discharge the
excess pressure.
Therefore check the expansion vessel pre-charge
pressure annually.
Check whether the installed expansion vessel is ade-
quate for the system water volume (GB only).
Commissioning, inspection, maintenance
4. Check the light barrier function in the "Diagnosis"
menu.
Note
Operating states, actuators and sensors can be
checked under "Diagnosis" in the "Service" menu.
See page 113.
Carry out this test on a cold system.
1. Drain the system until "0" is shown on the pressure
indicator.
2. If the pre-charge pressure of the expansion vessel
is lower than the static system pressure: Top up
with nitrogen until the pre-charge pressure is 0.1 to
0.2 bar (10 to 20 kPa) higher than the static system
pressure.
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