47
4.16 Gas/Air Valve Setup Procedure
Checking the CO
2
1. The combustion (CO
2
) may be checked at maximum
rate using a suitably calibrated analyser after running
the boiler for several minutes.
2. To do this it is necessary to set the boiler to
#
Calibration Mode
$
.
3. Ensure that all external controls are calling for heat.
The actual current boiler temperature is shown on the
display.
4. Turn both temperature control knobs fully
anticlockwise, then quickly turn the DHW temperature
knob
1
/
4
clockwise twice and back fully anticlockwise.
5. The display will now alternate between
#
SF
$
and the
current boiler temperature and both green LEDs will
flash.
6. Turn the CH temperature knob fully clockwise. As
the knob is turned the display will change, indicating
the percentage of maximum fan speed.
7. The display will show
#
00
$
, indicating maximum rate,
then revert to
#
P
#
alternating with the current boiler
temperature.
8. Remove the plug from the flue adaptor test point.
Insert the analyser probe and allow time for the
reading to settle.
The CO
2
should be 8.9% ± 0.2
9. It is possible to alter the CO
2
by adjustment of the
gas valve. At maximum rate the
#
Max. Rate
$
throttle
adjustment screw should be turned clockwise to
decrease CO
2
, anti-clockwise to increase CO
2
using a
suitable 2.5mm hexagon key, until the correct reading
is obtained.
10. 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 8.6% ± 0.2.
11. If at minimum CO
2
is not correct please ring our
after sales service department.
12. 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 DHW knob.
MAX0031B
Air/Gas
Ratio Valve
Top View
I
nlet
Pressure
Test
Point
Outlet
Pressure
Test
Point
S
ignal
sensing
tube
connected
to
Fan
Air
S
ignal
Connection
Offset
Ad
j
ustment
Throttle
Ad
j
ustment
Flue Adaptor
Test Point
Min Gas Rate
Max Gas Rate
Burner
Pressure
(mb)
0.6 - 0.8
6.8 - 7.2
Gas
Rate
(m
3
/hr)
0.7 - 0.74
2.48 - 2.74
CO
(ppm)
2 - 30
30 - 80
CO
2
(%)
8.4 - 8.8
8.7 - 9.2
© Baxi Heating UK Ltd 2012