Inspection and maintenance
63
Greenstar 4000 – 6 720 891 161 (2020/09)
8.8 Setting the air/gas ratio
NOTICE
Setting the air/gas ratio
▶ The air/gas ratio is factory set and should not need to be adjusted. If
found to be out of tolerance and when all other possible causes have
been checked, please contact the Worcester Bosch Group helpline
0330 123 3366.
NOTICE
Combustion testing
▶The checking of the air/gas ratio must be carried out by a competent
registered gas engineer, such as a Gas Safe registered engineer or
British Gas engineer.
▶ Checking of the air/gas ratio must not be attempted unless the
person carrying out the test is equipped with a flue gas analyser
conforming to BS7927 and is competent in its use.
All CO/CO
2
readings must be taken with the combustion chamber cover
ON.
Adjustments can only be made with the cover off.
CO
2
should be measured 10 minutes after firing the appliance.
Adjusting the minimum rated output settings
With the appliance in minimum rated output.
▶ Remove the seal from the adjusting screw of the gas valve (only gas
valve is shown in the below Figure 82) and set the CO
2
content for
minimum rated output.
Fig. 82 Setting the CO
2
content (above: SIT valve, below: Honeywell
valves)
[1] Gas valve - NG
[2] Gas valve - LPG
▶ Re-check settings at maximum and minimum rated output and re-
adjust if required.
▶ Seal the gas valve minimum adjustment.
▶ Exit the chimney sweep mode.
▶Enter the CO
2
contents in the servicing record.
Adjusting the maximum rated output settings (LPG appliances)
With the appliance in maximum rated output.
▶ Insert the hex tool into the adjusting screw of the gas valve (as shown
in the below Figure 83) and set the CO
2
content for maximum rated
output.
Fig. 83 Setting the CO
2
content
▶ Re-check settings at minimum and maximum rated output and re-
adjust if required.
▶ Exit the chimney sweep mode.
▶Enter the CO
2
contents in the servicing record.
0010035321-001
MIN. %
MIN. %
4mm
T40
1 2
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