7. Take a T piece and connect it as follows:
7.1. Connect one end of the T piece to the hose from measuring
point 3.
7.2. Connect one end of the T piece to a large plastic syringe.
7.3. Connect the other end of the T piece to a pressure gauge.
8. Push the syringe in very slowly until the pressure gauge indicates the
minimum inlet gas pressure.
9. Check the measured pressure for about 30 seconds.
If the pressure decreases by more than half, this indicates a gas
leak: Replace the gas control valve or the VPS if necessary.
10. To check the VPS switch value, remove the plug from the VPS.
11. Connect an ohmmeter to terminals 2 and 3 of the VPS.
12. Release any pressure from the gas control valve:
12.1. Remove the hose from measuring point 3 of the gas control
valve.
12.2. Wait 10 seconds.
12.3. Reconnect the hose to measuring point 3.
13. Push the syringe in very slowly until the ohmmeter indicates 0 Ω.
14. Check the measured pressure at that point.
If the measured pressure differs by more than 2 mbar from the value
as set on the VPS, set the pressure switch to the actual measured
value or replace the VPS.
11.3.9 Checking the minimum gas pressure switch (GPS)
1. Switch off the boiler.
Fig.118 Checking the VPS for leaks
AD-3001574-01
≥ 0.5 x
≤ 0.5 x
X mbar
(+)
7
9
8
30 sec
Fig.119 Connecting an ohmmeter
AD-3001575-01
VPS
GPS
VPS
GPS
GPS
VPS
11
10
5/6
7/8/9
10
Fig.120 Releasing the pressure
AD-3001576-01
3
3
3
2
3
2
10 sec
10 sec
12
12.1
12.2
12.3
Fig.121 Checking the switch value
AD-3001577-01
0 Ohm
X mbar
(+)
14
13
11 Maintenance
152
C 340 / C 640
7762666 - v.02 - 29092020
