7 Commissioning
Combi 2
47
Fig.53
Gas valve
7.4.4
Calibrating the gas valve
V
Gas flow rate setting screw - 4mm Allen key
K
OFFSET setting screw - Torx 40 (T40)
Remove the boiler door to take measurements or make adjustments.
Calibration of the MAXIMUM heat input
Check that the CO
2
measured in the exhaust pipe, with the boiler
operating at maximum heat input, is as indicated in the table entitled
"Service settings".
If incorrect:
Put the boiler into chimney sweep high mode "H". Let the CO
2
value
stabilise.
Important
Remove the Allen key to stabilise the CO
2
value if adjustment is
required.
Adjust the setting screw (V) located on the gas valve. Turn the screw
clockwise to increase the content of CO
2
and anti-clockwise to decrease
it.
Baxi Combi
424 -
430
CO
2
% (maximum)
8.8 to 9.4
* Values for G20 gas type only. For G20+20%H2 calibration of the
gas valve refer to O
2
%.
Calibration of the REDUCED heat input
Check that the measurement in the exhaust pipe, with the boiler
operating at minimum heat input, is as indicated in the table entitled
"Service settings".
If incorrect:
Remove the Offset setting screw plug (K) using the Torx driver.
The Offset setting screw is accessible after removing the Offset
setting screw plug (K).
Put the boiler into chimney sweep low mode. Let the CO
2
value
stabilise.
Important
Remove the Torx driver to stabilise the CO
2
value if
adjustment is required.
Adjust the Offset setting screw located on the gas valve. Turn the
screw clockwise to increase the content of CO2 and anti-clockwise
to decrease it.
Baxi Combi
424 -
430
CO
2
% (maximum)
8 1 to 8.6
* Values for G20 gas type only. For G20+20%H2 calibration of the
gas valve refer to O
2
%.