VOKERA Mynute EHE Installation & Servicing Instructions Manual - page 22
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7.3
CHECKING AND ADJUSTING BURNER PRESSURE
(fig. 16)
Although the burner pressure is factory set, it is necessary
to check it during commissioning, servicing, or if the gas
valve has been removed.
Isolate the appliance from the electrical supply and attach
a suitable manometer to the gas valve outlet test nipple.
Temporarily fit a jumper tag at JP2 on the PCB.
Restore the electrical supply and ensure that all controls
are calling for heat, i.e. ensure the boiler is working under
full load condition.
MAXIMUM
Check that the value displayed on the manometer, corre-
sponds with the relative (maximum) value for the appropri-
ate gas type (Nat. Gas - see section 2, LPG -see section 10).
If an incorrect value is displayed, proceed to 7.3.1. Once the
maximum gas pressure has been checked and/or ad-
justed, proceed to check/adjust the minimum gas pressure
MINIMUM
Once the maximum burner pressure has been checked
and/or adjusted, remove one of the grey wires from the
modulating coil of the gas valve. Check that the value
displayed on the manometer, corresponds with the relative
(minimum) value for the appropriate gas type (Nat. Gas -
see section 2, LPG - see section 10). If an incorrect value
is displayed, proceed to 7.3.2.
When checking and/or adjustment has been completed,
isolate the appliance from the electrical supply, replace the
protective cap, refit the grey wire to the modulating coil,
remove the manometer, and tighten the outlet test nipple.
IMPORTANT, A GAS SOUNDNESS CHECK MUST BE
CARRIED OUT.
7.3.1
SETTING THE MAXIMUM BURNER PRESSURE (fig.
34)
Follow the procedure as detailed in 7.3 and compare the reading
on the manometer with the value described in section 2. If
adjustment is required, remove the protective cap from the gas
valve modulating coil assembly and turn the outer (10mm) nut
clockwise to increase, or counter-clockwise to decrease the
burner pressure.
NOTE
Always check and/or adjust the minimum and maximum
gas pressures whilst the appliance is operating under full
load conditions, i.e. heating and hot water.
7.3.2
SETTING THE MIMIMUM BURNER PRESSURE (fig. 35)
Once the maximum burner pressure has been checked
and/or adjusted, remove one of the grey wires from the
modulating coil. Compare the reading on the manometer
with the value described in 2.3. If adjustment is required,
turn the inner (red) crosshead screw clockwise to increase,
or counter-clockwise to decrease the burner pressure,
whilst ensuring that the outer (10mm) nut does not move.
When checking and/or adjustment has been completed,
isolate the appliance from the electrical supply, replace the
protective cap, refit the grey wire to the modulating coil,
remove the manometer and tighten the outlet test nipple.
IMPORTANT, A GAS SOUNDNESS CHECK MUST BE
CARRIED OUT.
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
appliance, however you must check that the burner pres-
sures are set correctly (see 7.3).
●
Isolate the appliance from the electrical supply and turn
the mode selector switch to the
OFF
position (
).
●
Locate and remove the CO test point sealing screw (fig.
35).
●
Insert the flue gas analyser probe into the test point.
●
Restore the electrical supply to the appliance
●
Remove the mode selector knob and turn the shaft fully
clockwise (see fig. 36).
●
The boiler will now enter the combustion analysis mode
(CO mode) for a period of 15 minutes, signified by the
LED flashing yellow. During this time, the boiler will
remain on full gas.
●
Once the flue gas analysis has been made, turn the shaft
back to the required position and replace the mode
selector knob.
●
Remove the probe and replace the sealing screw.
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
correct charge pressure should be 1.0 bar ± 0.1 bar.
If the charge pressure is less, use a suitable pump to
increase the charge.
Fig. 33
Fig. 34
Fig. 35
Fig. 36
ON
OFF
RESET
1st sector
3rd sector
SARA sector
40 °C
80 °C