Checking The Expansion Vessel And System Pressure - Viessmann Vitoligno 300-C Installation And Service Instructions For Contractors

Commissioning, inspection, maintenance

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 gauge will indicate a higher pressure of 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).
Carry out this test on a cold system.
1. Drain the system until the pressure gauge shows
"0".
Alternatively, close the cap valve on the expansion
vessel and reduce the pressure until the pressure
gauge indicates "0".
Checking the function of the safety valves
Emissions test
After commissioning, an emissions test must be car-
ried out.
Preparation
Clean flue gas routes and chimney at least 3 days
■
before testing.
■ If the Lambda probe shows less than 20 % O
cold, clean the Lambda probe and calibrate.
Test point
For the test point, observe the following:
Place measuring head centrally in flue pipe
■
Not directly next to the flue gas fan
■
■ Not upstream of a flue bend
■ If present in the test route: Tightly close chimney
damper/draught stabiliser.
Testing
For consistent test results, continuous heating opera-
tion is essential. Therefore avoid modulating heating
operation.
In test mode, the boiler heats with a consistent output
until the maximum boiler water temperature has been
reached.
1. Ensure heat draw-off.
Avoid modulating heating operation.
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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.
3. Top up with water until the charge pressure of the
cooled system is at least 1.0 bar (0.1 MPa), and is
0.1 to 0.2 bar (10 to 20 kPa) higher than the pre-
charge pressure of the expansion vessel.
Permiss. operating pressure: 3 bar (0.3 MPa)
Carry out repeat emissions tests in the manner descri-
bed.
Operate the boiler continuously for at least 24 hours
■
between cleaning and testing.
when ■ Allow boiler to cool down before testing.
2
■ Upstream of the test point: Distance to the boiler flue
outlet or to the last pipe bend: 2x Ø of the flue pipe
Downstream of the test point: Calming stretch
■
(straight pipe) with at least 1 to 2x Ø of the flue pipe
2. Start the boiler.
3. In the standard menu: Activate "Test mode".
The display shows "Preparation". The boiler heats
until load operation.
"Test active" then appears as soon as constant
heating operation has been reached.