Checking The Neutralising System (If Installed); Checking The Flow Limiter (Only For Gas Condensing Combi Boilers); Checking The Expansion Vessel And System Pressure; Checking The Function Of Safety Valves - Viessmann Vitodens 200-W Installation And Service Instructions For Contractors

Installing the burner
4. Connect cables from fan motor
ionisation electrode
C
tab .
E

Checking the neutralising system (if installed)

Checking the flow limiter (only for gas condensing combi boilers)

C
B
A
Fig. 29

Checking the expansion vessel and system pressure

Note
The expansion vessel can lose some of its charge
pressure after some time in use. 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 too can
respond and discharge excess pressure.
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 or close the cap valve on the
expansion vessel and reduce the pressure until the
pressure gauge indicates "0".

Checking the function of safety valves

(cont.)
A , gas train B ,
, ignition unit and earth
D
Commissioning, inspection, maintenance
1. Switch OFF the control unit, shut off the cold water
line and drain the DHW side of the boiler.
2. Undo Allen screws
A .
Note
Residual water may escape during dismantling.
3. Remove flow switch
B
downwards.
4. Check flow limiter ; replace if scaled up or dam-
C
aged.
Refit flow switch B .
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)
and extract flow limiter C
33