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Inspection and maintenance
Fig. 72 Removing the front casing
9.4
Check working gas inlet pressure
NOTICE
Gas inlet pressure
▶ Do not continue with the other checks if the correct gas inlet pressure
can not be achieved at maximum output.
▶ Check the gas supply working pressures in the system conform to the
readings shown in the table shown in chapter 6.5 "Checking gas inlet
pressure".
9.5
Flue gas analysis
NOTICE
Combustion testing
▶ Combustion testing must be carried out by a competent person.
Testing must not be attempted unless the person carrying out the
combustion check is equipped with a calibrated flue gas analyser
conforming to BS 7967 and is competent in its use.
Flue gas analysis
▶ Ensure that the gas inlet pressure has been checked and is
satisfactory.
▶ Refit the test point plugs after the test has been completed.
▶ Set the appliance to maximum and minimum output in chimney
sweep mode ( 6.4 "Chimney sweep mode") for the flue gas
analysis checks.
▶ Check that the readings conform to those given in the following
tables. In addition to CO and CO/CO
maximum and minimum CO
2
54
1.
2.
1
0010042657-002
ratio checks also check the
2
percentage reading.
Appliance combustion contents settings
CO
Reading
2
Natural Gas - Maximum rated Output
Between 8.6 and 9.4 %
Natural Gas - Minimum rated Output
A minimum of 0.5 lower than the maximum reading
taken but above 8.1 %. Offset pressure needs to be
adjusted according to - 5 Pa pressure at minimum
output.
1) Should be measured 10 minutes after firing the appliance
Table 32 CO
settings
2
If the CO
is out of tolerance then please check:
2
▶ The gas inlet pressure.
▶ The gas rate.
▶ The flue and air intake, plus any possible blockages in the condensate
disposal.
▶ The condition of burner.
▶ For leaks or obstructions in the exhaust paths.
▶ That the injector is clean.
After all checks have been completed and the CO
then contact Worcester, Bosch Group helpline 0330 123 3366 before
making any adjustment to the gas valve.
9.6
Checking the flue integrity
NOTICE
▶ Check flue joints are secure, the terminal and the terminal guard, if
fitted are clear and undamaged.
▶ Combustion testing must be carried out to BS 7967 by a competent
person. Testing must not be attempted unless the person carrying
out the combustion check is equipped with a calibrated Combustion
Analyser conforming to BS EN 50379 and is competent in its use.
Flue gas analysis
▶ Ensure that the gas inlet pressure has been checked and is
satisfactory.
▶ Refit the test point plugs after the test has been completed.
▶ Refer to chapter 6.9 "Checking flue integrity" and check that the
readings conform to those given, confirming flue system and
combustion circuit are ok.
9.7
Cleaning the heat exchanger
WARNING
Gaskets and seals - gas related components
▶ Burner door lip seal must be replaced if disturbed.
▶ Other gaskets/seals must be checked and replaced where necessary.
▶ Do not attempt the cleaning procedure unless new gaskets and seals
are available.
▶ After servicing of heat exchanger, check back-flow prevention valve
(non-return flap) and gas-air pipe seal on the burner door interface.
▶ Ensure that the gaskets are positioned correctly.
Maintenance tools
For this operation you need:
• A vacuum cleaner
• A soft nylon hand brush
• Mains water
Greenstar 1000 – 6721835943 (2023/08)
CO Reading
1)
<250ppm
<250ppm
is still out of tolerance
2
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