25
7.3 CHECKING THE CO
2
AND ADJUSTING THE
GAS VALVE
THE GAS VALVE MUST BE SET-UP OR ADJUSTED WITH
THE AID OF A PROPERLY CALIBRATED FLUE GAS
ANALYSER.
Isolate the appliance from the electrical supply and remove
the appliance casing as described in 4.7.1, to gain access to
the printed circuit board, locate and open the closing plug on
the dash board (L2), Restore the electrical supply to the boiler
and switch the boiler to the OFF mode. locate and press the
CO button (see fi g. 40 pos. SW1). Press the button the num-
ber of times according the function requirement as par 7.3.1.
Set the fl ue gas analyser to read CO2 and insert the probe
into the fl ue analysis test point.
Fig. 40
L2
SW1
use the supplied
screwdriver to push the
CO botton (SW1)
7.3.2 GAS VALVE MAXIMUM SETTING
Set the CO
2
button at maximum heating (see 7.3.1), once the
maximum heating is obtained (only yellow led blinking) check
that it corresponds with the appropriate CO
2
value (Maximum)
for the respective appliance (see 2.11). If the CO
2
reading is
correct, proceed to gas valve minimum setting (7.3.3).
However, if the CO
2
reading is incorrect, the maximum gas
pressure must be adjusted as follows:
using a 2.5mm Allen key, very slowly turn the maximum ad-
justment screw (see fi g. 41) – clockwise to decrease, counter
clockwise to increase – until the correct value is displayed on
the CO
2
analyser (allow time for the analyser to stabilise).
7.3.3 GAS VALVE MINIMUM SETTING
Set the CO2 button at minimum (see 7.3.1), once the minimum
is obtained (yellow led bl green led fi xed) check that it
corresponds with the appropriate CO2 value (Minimum) for the
respective appliance (see 2.11). If the CO2 reading is correct,
proceed to completion (7.3.4).
However, if the CO2 reading is incorrect, the minimum gas
pressure must be adjusted as follows:
• locate the minimum adjustment screw (fi g. 41), using a suit-
able screwdriver remove the protection plug
• using a 4mm Allen key, very slowly turn the minimum adjust-
ment screw (see fi g. 41) - clockwise to increase, counter
clockwise to decrease - until the correct value is displayed
on the CO2 analyser (allow time for the analyser to stabilise).
7.3.4 COMPLETION
On completion of the combustion analysis check and/or any
gas valve adjustment, refi t the plug (fi g. 40
L2
) and move the
mode selector through
position. Remove the test probe
from the test point and refi t the sealing screw/s and/or cap.
IMPORTANT
A GAS TIGHTNESS CHECK MUST BE CARRIED OUT IF
ANY GAS CARRYING COMPONENTS HAVE BEEN REMO-
VED, REPLACED OR DISTURBED.
7.4 COMBUSTION ANALYSIS TEST
A combustion analysis check can easily be carried out on the
appliance via the test points located on the top of the appli-
ance (see 7.3).
Insert the fl ue gas analyser probe into the fl ue gas test point
7.3.1 CO
2
FUNCTION SETTINGS
Locate the CO
button (see 7.3)
Select the main selector switch in position
CO
2
FUNCTIONS
ACTION ON THE BUTTON
LED STATUS
combustion analysis mode
press once = burner running at maximum heating
ACO
gas valve maximun setting (*)
press twice = burner running at maximum absolute
ACO
gas valve minimum setting
press three time = burner running at minimum
ACO
(*) this step has not to be used for the system boiler. If you fi nd in this situation press the button once again.
NOTE
1 - Any additional pressing of CO
button after the third time the burner switched between maximum absolute and minimum.
2 - To restart the CO
function it is necessary to pass throught the
position with the main selector switch
Operate the boiler in combustion analysis mode (see 7.3.1)
and compare the values with those shown in section 2 (Nat.
Gas) or section 10 (LPG). If different adjust the gas valve
according to 7.3.1, 7.3.2, & 7.3.3.
Note:
If a measured CO/CO2 ratio of 0.004/1 or less AND a
CO reading of less than 350ppm cannot be achieved, please
contact Vokera technical for advice.
7.5 CHECKING THE EXPANSION VESSEL
Carry out the component removal procedure as described in
6.4. You must ensure that the boiler is completely drained of
water. Using a suitable pressure gauge, remove dust cap on
expansion vessel and check the charge pressure. The cor-
rect charge pressure should be 1.0 bar ± 0.1 bar. If the charge
pressure is less, use a suitable pump to increase the charge.
NOTE
You must ensure the drain valve is in the open position whilst
re-charging takes place. Replace the dust cap and carry out
the relevant commissioning procedure (section 5).
fi g. 41
Minimum
screw
Inlet gas pressure
connection
Compensation pipe
connection
Maximum
screw
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