Setting The Air/Gas Ratio; Checking And, If Required, Adjusting The Gas/Air; Ratio - Worcester GR8700iW 35 C Installation And Maintenance Instructions Manual

Inspection and maintenance
8.10

Setting the air/gas ratio

NOTICE:
Setting the air/gas ratio
▶ The gas valve and venturi are 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 setting 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.
▶ Setting 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 readings must be taken with the combustion chamber cover
2
ON.
Adjustments can only be made with the cover off.
CO should be measured 10 minutes after firing the appliance.
2
8.10.1 Checking and, if required, adjusting the gas/air ratio
▶ Switch off the appliance.
▶ Remove the front cover.
▶ Remove the combustion cover.
Fig. 94 Removing the combustion cover
62
2.
1.
0 010 007 441-001
1
Fig. 95 Setting the adjustable venturi
[1] Security Seal
[2] Adjustable venturi
▶ Switch on the appliance.
▶ Remove the plug from the flue gas test port.
▶ Push the flue gas probe centrally into the flue gas test port.
▶ Seal the test point.
Fig. 96 Flue gas test port
▶ To ensure heat transfer: open the radiator valves.
▶ Set the chimney sweep mode and start up the appliance at maximum
rated output.
▶ Measure the CO or O content.
2 2
▶ Check the CO or O content at maximum rated output according to
2 2
Tab. 23 and adjust if required.
Security Seal [1] ( Fig. 95) must be removed before adjusting the Max
CO setting. Once adjustment has been made the seal must be replaced
2
with part number 8737708988.
▶ To increase the CO content, remove seal [1] and turn the adjustable
2
venturi to the left.
▶ To reduce the CO content, remove seal [1] and turn the adjustable
2
venturi to the right.
Greenstar 8000 Style – 6720883864 (2019/02)
2
0 010 020 540-002
0010023633-001