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SERVICING AND SPARES
6.2
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.
Setting the CO
2
When running in the performance test mode ensure the
motorised valve(s) are open to avoid the boiler cycling
during the commissioning operation
1. Connect manometer to inlet test point on the gas valve.
▶ To adjust the CO
it will be necessary to first operate the boiler at
2
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.
The control will resume normal operation after 15
minutes or if the performance test button is pressed for
over a second.
3. Using a flat blade screwdriver set the CO
referring to the table below.
CO
should be measured 10 minutes after firing the
2
appliance.
CO
setting
2
Gas type
maximum
Greenstar 30CDi Classic Regular
Natural gas
9.6% ±0.4
LPG
11.5% ±0.4
Greenstar 40CDi Classic Regular
Natural gas
9.7% ±0.4
LPG
11.5% ±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)
▶ 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
; it should now be at the figure for minimum output.
2
▶ 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
▶ 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.
38
via the max adjuster
2
CO
setting
2
minimum
ErP
9.0% ±0.4
10.5% ±0.4
ErP
9.1% ±0.4
10.5% ±0.4
.
2
Max
adjust
Min
adjust
4mm
Inlet pressure
test point
Fig. 68 Setting the Air/Gas ratio
6720647361-48.1Wo
6 720 815 723 (2015/05)
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