Servicing and spares | 41
6 720 ... ... (YYYY/MM)Product Name
▶ Press the / button together with the button to enter the
“Chimney sweep mode” , the display shows the current flow
temperature and flashes the percentage heat output in the
alphanumeric display. The burner symbol will be shown in the
display.
Press the + or - buttons until the required percentage output is
displayed. Set the output to 100% initially.
– The boiler will ramp up to maximum output in approximately
30 to 35 seconds.
▶ Run the boiler at maximum output for at least 10 minutes.
▶ Check the CO/CO
2
readings against the information in table 23.
Fig. 58
▶ Check CO is less than 200ppm.
▶ Set the boiler to minimum power.
– The boiler will take 30 to 35 seconds to ramp down to minimum
output.
– Allow the boiler to stabilise at minimum output.
▶ Check the CO/CO
2
readings against the information in table 23.
▶ Check that the CO is less than 200ppm.
▶ Return the boiler to maximum and re-check the CO/CO
2
.
– The boiler will take approximately 30 to 35 seconds to ramp up to
maximum output.
– Allow the boiler to stabilise at maximum output.
▶ If correct, press the button and the boiler will return to normal
operation.
▶ Re-assemble and refit boiler case.
10.8 Setting the air/gas ratio
If the CO
2
maximum or minimum value are incorrect, the gas valve can be
adjusted as follows:
▶ Set the boiler to maximum output
▶ Remove the plastic dust cover [1]
▶ Using a flat blade screwdriver adjust the maximum CO
2
setting [2]
with reference to table 23, turn clockwise to reduce or
anti-clockwise to increase the setting.
▶ Set the boiler to minimum output
▶ Measure the CO
2
value, it should be at the figure for minimum output
shown in table 23
▶ It not, remove the brass dust cap [3] from the minimum adjuster
▶ Using a 4mm Allen key to adjust the minimum setting [4] on the gas
valve until it is correct, turn clockwise to increase and anti-clockwise
to decrease the setting
▶ Return the boiler to maximum output and check the CO
2
value
▶ If this is correct, then return the boiler to normal operation
▶ Remove the manometer from the flue gas sample point
▶ Replace the flue gas sample point cap
▶ Replace the brass dust [3] cover on the minimum adjuster [4]
▶ Fit a new plastic dust cover [1] on the maximum adjuster [2]
Fig. 59 CO
2
adjustment
[1] Maximum adjuster plastic dust cover
[2] Maximum adjustment
[3] Minimum adjuster brass dust cover
[4] Minimum adjustment
If the CO
2
is still out of tolerance then please check the:
▶ gas inlet pressure
▶ gas rate
▶ fan pressure
▶ flue and air intake, plus any blockages in the condensate disposal
NOTICE: Minimum CO
2
▶ The minimum CO
2
reading must be at least 0.1 lower
that the maximum CO
2
reading.
GAS TYPE
CO
2
max % setting CO
2
min % setting
G20 Natural Gas (42kW) 9.5 (+0.4/ -0.0) 9.4 (+0.4/ -0.0)
G20 Natural Gas (16 & 32kW) 9.4 (+0.4/ -0.0) 8.6 (+0.4/ -0.0)
G25 Natural gas (42kW) 7.6 (+0.4/ -0.0) 7.5 (+0.4/ -0.0)
G25 Natural Gas (16 & 32kW) 7.5 (+0.4/ -0.0) 6.9 (+0.4/ -0.0)
G31 LPG (42kW) 10.9 (+0.4/ -0.0) 10.8 (+0.4/ -0.0)
G31 LPG (16 & 32kW) 10.8 (+0.4/ -0.0) 10.5 (+0.4/ -0.0)
CO - less than 200 ppm (0.002 ratio)
Table 23 CO/CO
2
settings
6720809859-25.1Wo
The control will return to normal operation after 30
minutes or press the button.
The CO
2
should be measured 10 minutes after setting
the boiler to maximum
6720809859-62.1Wo
3
1
4
2
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