Potterton Envoy 30 Installation & Service Instructions Manual page 17

COMMISSIONING – Page 17
Switch the boiler control switch to the " " position and
the character " " will be displayed. After approximately
10 seconds the boiler should light. Due to the presence
of air in the gas supply it is possible that the boiler will
not light at the first attempt but will automatically cycle
and make two further attempts. If the boiler still fails to
light it will go to lockout indicated by the character " "
shown flashing on the display. If this should occur wait
10 seconds then press the lockout reset button and the
boiler will go through another start sequence.
It should be noted that the boiler control continuously
monitors the temperature rise across the heat
exchanger. Therefore, if the system is not correctly
vented, air passing through the pump may lead to boiler
shut down with the character "2" being displayed. If this
occurs thoroughly vent the system and press the reset
button.
If the boiler fails to start after 1 or 2 attempts refer to
fault finding section on Page 27
BURNER PRESSURE
This appliance is fitted with a Gas/Air ratio control
mixing valve. This gas valve ensures that the correct
amount of gas is delivered to the burner to match the
available air supply under all operating conditions.
THE BURNER PRESSURE AND GAS RATE HAVE
BEEN PRECISELY SET AND CHECKED DURING
MANUFACTURE AND NO ATTEMPT SHOULD BE
MADE TO ADJUST IT.
To check the correct operation of the gas valve follow
the instructions below carefully.
a. A good indication of correct operation of the boiler
will be obtained by measuring the gas rate at the
gas meter.
1. Run the appliance for at least 10 minutes.
2. With all other gas appliances turned off measure
the gas rate at the meter for a period of at least 5
minutes. Check that the measured rate is within ±
5% of the rate stated on the data plate.
b. To measure the burner pressure.
1. Turn off the gas service cock. Fit a pressure
gauge to the gas inlet pressure tapping on the gas
control valve. Connect a differential pressure
gauge or 'U' tube manometer between the burner
pressure gauge tapping (high pressure side) and
the reference pressure tapping (low pressure side)
on the gas valve ( see Fig. 13).
2. Turn on the gas service cock and run the
appliance for at least 10 minutes. Check that the
gas inlet pressure is between 19-20 mbar.
3. Check that the differential burner pressure is
within ± 1.0 mbar of that stated on the data plate.
4. Turn off the gas service cock and remove the
pressure gauge and replace the pressure tapping
sealing screws on the gas valve.
Should the gas rate or differential burner pressure fall
outside the specified range run the boiler for a further 10
mins and carry out a recheck, if after rechecking either the
gas rate or the burner pressure falls outside the tolerance
specified, Potterton Myson Service Department should be
called as specialist equipment is required to enable
adjustment to be made.
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