COMMISSIONING: CO AND COMBUSTION RATIO CHECK
SET BOILER TO MAXIMUM RATE
In accordance with, section 7.3, set boiler to operate at maximum rate (full load condition). Allow sufficient time for combustion to
stabilise. , insert analyser probe into air inlet sampling point.
Is O2 ≥20.6%
and CO2 < 0.2%?
Verify flue integrity
Analyser readings indicate
that combustion products
and inlet air are mixing.
Further investigation of the
flue is therefore required.
Check that flue components
are correctly assembled,
fixed and supported as per
boiler/flue instructions.
Check that flue and flue
terminal are not obstructed.
Is O2 ≥20.6%
and CO2 < 0.2%?
CHECK CO AND
COMBUSTION RATIO
AT MAXIMUM RATE
With boiler still set at
maximum rate, insert
analyser probe into flue
gas sampling point.
Allow readings to
stabilise before
di
Is CO less than
350ppm AND
CO/CO
2
ratio less
than 0.004?
YES
N
O
YES
NO
Check all seals
around the appliance
burner, internal flue
seals, door and case
seals. Rectify where
necessary.
Is CO less
than 350ppm
AND
CO/CO
2
ratio
less than
0.004?
CHECK CO AND COMBUSTION
RATIO AT MINIMUM RATE
With boiler set at minimum rate,
insert analyser probe into flue
gas sampling point. Allow
readings to stabilise before
recording.
NO
Turn off appliance and
call Vokera’s technical
helpline for advice.
The appliance must not
be commissioned until
problems are identified
and resolved.
Turn off appliance and call
Vokera’s technical helpline
for advice.
The appliance must not be
commissioned until
problems are identified and
resolved. If commissioning
cannot be fully completed,
the appliance must be
disconnected from the gas
supply in accordance with
the GSIUR.
NOTE:
Check and record CO and
combustion ratio at both
maximum AND minimum rate
before contacting the Vokera
SET BOILER TO
MINIMUM RATE
In accordance with
section 7.3, set
boiler to operate at
minimum rate (to
minimum load
condition). Allow
sufficient time for
combustion to
stabilise.
YES
Is CO < 350ppm
and CO/CO
2
ratio
less
than 0.004 ?
NO
Boiler is operating satisfactorily
No further actions required.
Ensure test points are capped, boiler case is correctly replaced and all other commissioning procedures are completed.
Complete Benchmark Checklist, recording CO and combustion ratio readings as required.
NOTE
The air/gas ratio valve is factory-set and must not be
adjusted during commissioning unless this action is
recommended, following contact with the Vokera
technical help line. If any such adjustment is
recommended and further checking of the boiler is
required, the engineer must be competent to carry out
this work and to use the flue gas analyser accordingly.
If the boiler requires conversion to operate with a
different gas family (e.g., conversion from natural gas
to LPG) separate guidance will be provided by the
Vokera technical help line and must be followed.
NO
BEFORE CO AND COMBUSTION RATIO CHECK
The installation instructions should have been followed, gas
type verified and gas supply pressure/rate checked as required
prior to commissioning.
As part of the installation process,
ESPECIALLY WHERE A
FLUE HAS BEEN FITTED BY PERSONS OTHER THAN THE
BOILER INSTALLER, visually check the integrity of the whole
flue system to confirm that all components are correctly
assembled, fixed and supported. Check that the maximum flue
lengths have not been exceeded and all guidance has been
followed (e.g. Technical Bulletin 008).
The flue gas analyser should be of the correct type, as specified
by BS 7967.
Before use, the flue gas analyser should have been maintained
and calibrated as specified by the manufacturer. The installer
must have the relevant competence for use of the analyser.
Check and zero the analyser
IN FRESH AIR, as per analyser
manufacturer’s instructions.
YES
YES
