Blue Seal 203926, Руководство по обслуживанию

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Revision 7/F3527
© Moffat Ltd, November 2004
control and gas control valve operate on 24
volts AC through a 110 volt - 24 volt
transformer. For these models the thermostat
powers the transformer, whereas on 220-240
volt models the thermostat powers the ignition
control directly.
On the thermostat calling for heat, the
thermostat will switch power to the ignition
control. The ignition control will then power
the gas control valve to open the solenoids
and provide gas to the burner. At the same
time the ignition control will generate a high
voltage ignition spark sequence conveyed to
the ignition electrodes mounted at the front of
the burner and oven through a high tension
ignition cable. The spark and earth ignition
electrodes will spark across the end gap
between these two to ignite the burner.
On successful ignition of the burner the third
electrode, being a flame rectification rod, will
be in the burner flame. This provides the
ignition control with confirmation that the
burner is lit by establishing a micro-amp
current from the electrode to earth through the
flame due to combustion flames being ionised
and therefore able to conduct minute electrical
currents. The flame electrode is connected to
the ignition control with an insulated wire
conductor.
If this ignition sequence occurs correctly the
spark sequence will be stopped and the
burner will continue to operate until the
thermostat switches off and shuts down the
ignition control and consequently closes the
gas solenoid valve.
Should the ignition control not sense the
burner flame within a fixed ignition / spark
sequence period, the ignition control will lock-
out and turn off the gas solenoid valve on
220-240 volt models. Lock-out condition
requires the oven thermostat to be switched
off before operation can be restarted. On 110
volt models only, an unsuccessful ignition
attempt will be followed by a 30 second purge
with the gas control valve shut, then
re-attempt ignition automatically. 2 re-ignition
retries will be attempted. If unsuccessful the
ignition control will then lock-out and shut the
gas valve off.
If the ignition control loses the burner flame
during an on period, a re-ignition attempt will
be started automatically. If this is unsuccess-
ful the ignition will go to lock-out mode.
NOTE: Different voltage and market models
have different ignition sequence and
re-ignition specifications. Refer to appendix B
for specific model details.
The gas solenoid valve also includes the gas
regulator and on installation is adjusted to
achieve correct burner gas operating
pressure.
The G32 Turbofan convection oven features a
Roast-and-Hold system which can be used to
automatically set the oven to a fixed holding
temperature at the end of a timed cooking
period. When the Roast-and-Hold switch is
turned On the switch will illuminate and switch
on a relay found inside the control panel, at
the base of the control housing next to the
door microswitch. When the relay is switched
ON a normally closed switch pole on the relay
is opened and the normal power supply to the
oven thermostat is isolated. A second
normally open switch pole is closed and this
provides power to the 3 hour roast timer.
If the roast timer is in the Hold (vertical)
position the timer switch contacts will be in
their normally closed position and supply
power directly to the Hold thermostat located
behind the control panel. The Hold
thermostat is factory set to 75°C (167°F) and
will supply power to the ignition and gas
burner as required to maintain its preset
temperature.
The thermostat heating light will also cycle
On/Off as the Hold thermostat maintains
temperature.
In the Roast-and Hold mode the 3 hour timer
can be set to a selected roasting time. During
this time period the normally open switch
contacts of the timer are closed. The timer
has two change over switches and in this
position one is used to supply power to its
timing motor and the other is used to switch
power directly to the main oven thermostat.
During the 3 hour timer run-down period the
oven temperature will be controlled by the
main oven thermostat to the set temperature
and operate as previously described.
When the 3 hour timer has run down and
reached the Hold position the two switch
contacts change over to their normally closed
position which isolates power from the timer
motor and the oven thermostat. It also
switches power back to the oven hold
thermostat. At this point the temperature
control is now maintained by the hold
thermostat as previously described. To