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8.9.1
CO and combustion checks
The following combustion and flue integrity checks are mandatory from
April 2014 and these values must be recorded on the Benchmark check
list, at the back of this manual.
Once the gas rate and pressure have been confirmed as acceptable then
the CO and combustion checks can be undertaken.
The boiler case must be fitted whilst these checks are
carried out.
Set boiler to
START
maximum rate.
HERE
<
= less than
≥
= greater than
or equal to
No
Record values.
Do not adjust
the gas valve.
Turn off boiler and
call Worcester, Bosch
Group help line.
0330 123 3366
Fig. 72 Combustion check flow chart
6720814332 (2018/04)
Zero the analyser
in fresh air.
See notice above
O
≥ 20.6%
2
No
CO
< 0.2%
2
Yes
Check all seals around the
CO < 350ppm
burner, internal flue seals,
CO/CO
ratio
2
< 0.0035
Check CO and combustion
Yes
No
NOTICE: BEFORE CO AND COMBUSTION CHECKS:
▶ Refer to section 5.2 and section 8.7 a to verify gas
type, gas inlet pressure, and gas rate.
Visually check the integrity of the whole flue system
and confirm that all the components are correctly
assembled, fixed and supported.
▶ The flue gas analyser must be the correct type as
specified in BS 7967.
Before use the analyser must have been calibrated as
specified by the manufacturer.
The installer must be competent in the use of the
analyser.
Check and zero the analyser in fresh air as specified
by the manufacturer.
▶ The gas valve is factory set and must not be adjusted
during commissioning if found to be out of tolerance,
please contact the Worcester, Bosch Group help line
0330 123 3366.
Flue integrity test
using analyser
Verify flue integrity
and case seals.
Rectify where necessary.
ratio at minimum rate
CO < 350ppm
CO/CO
ratio
2
< 0.0035
Commissioning
O
≥ 20.6%
2
Yes
CO
< 0.2%
2
No
Check CO and
combustion ratio
at maximum rate
CO < 350ppm
No
CO/CO
2
< 0.0035
Yes
Set boiler to
minimum rate.
Boiler is operating
satisfactorily.
Yes
No further action
is required.
6720814332-1.1TD
ratio
35
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