SERVICING AND SPARES
6 720 806 548 (2013/02)34
▶ Fill the condensate trap with approximately 250 millilitres of water
and refit in reverse order
Fig. 55 Siphon removal
6.2 SETTING THE AIR/GAS RATIO
SETTING THE CO
2
1. Connect manometer to inlet test point on the gas valve.
▶To adjust the CO
2
it will be necessary to first operate the boiler at
maximum output.
▶ Press and hold down the performance test button for 10 seconds until
illuminated.
2. Turn central heating control to maximum; the boiler will then go to
maximum output.
3. Using a flat blade screwdriver set the CO
2
via the max adjuster
referring to the table below.
▶ Check CO is less than 200 ppm.
▶ Measure the gas inlet pressure at the gas valve test point; it should be
a maximum of 2.5mbar less than the pressure at the meter for natural
gas and a maximum of 4mbar less than the pressure at the regulator
for LPG.
4. Set the central heating control to minimum. This will make the boiler
go to minimum power.
5. Measure the CO
2
; it should now be at the figure for minimum output.
▶ If not, use a 4mm Allen key to adjust the min adjustment on the gas
valve until correct.
▶ Return to maximum and re-check the CO
2
.
▶ If correct press and hold down the performance test button for two
seconds; the button will cease to be illuminated and the blue power
indicator will be permanently illuminated.
▶ Remove manometer and re-seal inlet pressure point on gas valve.
▶ Fit new plastic sealing cover onto the max adjuster.
▶ Replace the brass screw over the min adjuster on the valve.
▶ Re-assemble and refit boiler case.
Fig. 56 Setting the Air/Gas ratio
NOTICE: Air/Gas ratio
▶ The setting of the gas ratio must be carried out by a
competent person.
Setting the air/gas ratio must not be attempted unless
the person carrying out the operation is equipped
with a combustion analyser conforming to BS 7927
and is competent in its use.
When running in the performance test mode ensure the
motorised valve(s) are open to avoid the boiler cycling
during the commissioning operation
The control will resume normal operation after 15
minutes or if the performance test button is pressed for
over a second.
CO
2
should be measured 10 minutes after firing the
appliance.
Gas type
CO
2
setting
maximum
CO
2
setting
minimum
Greenstar 30CDi
Natural gas 9.6% ±0.4 9.0% ±0.4
LPG 11.5% ±0.4 10.5% ±0.4
Greenstar 40CDi
Natural gas 9.7% ±0.4 9.1% ±0.4
LPG 11.5% ±0.4 10.5% ±0.4
NOTE: When checking an existing appliance the tolerance is ± 0.4%.
If checking after cleaning or component replacement or for adjustment
when the reading is outside the tolerance given above, then the
tolerance is ± 0.2%
CO - less than 200 ppm (0.002 ratio)
Inlet pressure
test point
Min
adjust
4mm
Max
adjust
6720647361-48.1Wo
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