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45
15.0 Combustion Check
© Baxi Heating UK Ltd 2007
15.1
Checking the CO
2
IMPORTANT: The CO
2
must be only be checked and
adjusted if a suitable calibrated combustion analyser is
available.
1. The combustion (CO
2
) may be checked after running the
boiler for several minutes. To do this it is necessary to set
the boiler to ‘Calibration Mode’.
2. Ensure that all external controls are calling for heat. The
actual current boiler temperature is shown on the display.
3. Turn both temperature control knobs fully anticlockwise,
then quickly turn the Calibration Control knob
1
/
4
clockwise
twice and back fully anticlockwise (Fig. 88).
4. The display will now alternate between ‘SF’ and the
current boiler temperature and both green LEDs will flash
(Figs. 89 & 90).
5. Turn the CH temperature knob fully clockwise. As the
knob is turned the display will change, indicating the fan
speed.
6. The display will show ‘00’, indicating maximum rate, then
revert to ‘P ‘ alternating with the current boiler temperature
(Figs 91, 92 & 93).
7. Remove the plug from the flue adaptor test point. Insert
the analyser probe and allow time for the reading to settle
(Fig. 94).
The CO
2
should be 8.7% ± 0.2
8. It is possible to alter the CO
2
by adjustment of the gas
valve. Remove the plastic cover from the ‘Max Rate’
adjustment screw. At maximum rate the ‘Max. Rate’
adjustment screw should be turned, using a suitable
hexagon key, until the correct reading is obtained (Fig. 95).
Turning clockwise will reduce the CO
2
. Anti-clockwise will
increase the CO
2.
9. The CO
2
must then be checked at minimum rate. Turn
the CH temperature knob fully anticlockwise. As the knob is
turned the display will change, indicating the fan speed.
When the display reads ‘ 0’ the boiler runs at minimum rate.
The CO
2
should be 8.4% ± 0.2.
10. With the boiler on minimum, the ‘Min. Rate’ adjustment
screw must be altered, using a suitable hexagon key, after
removing the cap (Fig. 95). Turning anti-clockwise will
reduce the CO
2
. Clockwise will increase the CO
2.
If the CO
2
is reset at either boiler rate it must be rechecked at the
other rate and also adjusted if required.
11. The ‘Calibration Function’ is maintained for 20 minutes
unless the maximum CH temperature is exceeded. The
function can be disabled at any time by turning the
Calibration Control knob.
Selector Switch
Display
Reset
bar
0
1
2
3
4
Central Heating
Temperature Control
Calibration Control
Fig. 89
Fig. 90
Fig. 91
Fig. 92
Fig. 93
Central Heating
Temperature Control
Calibration
Control
Fig. 88
x 2
Fig. 94
Max Rate
Adjustment Screw
(cover removed)
Min Rate
Adjustment Screw
(cap fitted)
Gas Valve
Fig. 95
Flue Adaptor Test
Point
Plug
Analyser Probe
