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Revision 4/F3591 © Moffat Ltd, August 2004
3.2 EXPLANATION OF CONTROL
SYSTEM
The E1100 Turbofan convection oven
features multi-function operator controls for
which a correct understanding of their
operation is required before carrying out any
service or fault repair work. The control
device functions are explained as follows:
A power switch on the control panel isolates
all to the controls of the oven. With the power
switch Off all functions of the oven are
inoperable.
With the power switch On (indicator
illuminated) power is directly supplied to the
60 minute bake timer, steam (water injection)
switch, light switch, and the temperature
control circuit. The oven circulation fan will
operate only when the thermostat is turned on
and the oven door is closed. The control
panel light switch will turn the oven lights on
when the door is closed only when the light
switch is held in. With the thermostat
switched on, the oven lights will come on
automatically when the door is opened, as this
is controlled by the door microswitch.
The 60 minute timer is a mechanical timer and
can therefore be operated with the oven’s
power switch On or Off. However, only with
the oven’s power switch On will the switch
contacts of the 60 minute timer turn on the
time-up buzzer and illuminate the time-up
indicator on the control panel. The buzzer
and time-up indicator provide indication that
the time setting has run down to zero and at
this point will remain On continuously until the
60 minute timer has been manually set back
to the Off (vertical) position. The 60 minute
timer does not control any other part of the
oven’s operating system as this timer is
independent of the temperature control and
heating system.
The steam (water injection) switch on the
control panel can be operated whenever the
power switch is On. The switch is momentary
like the light switch and when depressed, will
operate the electric solenoid valve at the rear
of the oven and inject water across the oven
fan from the flat spray (vertical) nozzle
positioned at the rear of the oven. Releasing
the steam button will close the solenoid valve.
This feature is used to instantaneously add
steam into the oven.
The temperature control of this oven is with a
capillary type thermostat which can be set to a
required cooking temperature.
The thermostat switch has a separate switch
body assembled onto the front from the shaft
assembly and when the thermostat is set to a
cooking temperature, the switch contacts turn
on the oven fan. The switch is closed (fan on)
whenever the thermostat is not in the Off
(vertical) position. The control panel indicator
light to the right of the thermostat knob cycles
On and Off with the thermostat to indicate
when the elements are on and the oven is
heating.
The E1100 Turbofan convection oven has 9.9
kW of electric heating elements, comprising of
three 3.3kW elements at the rear of the oven.
The elements are switched on and off by the
main oven thermostat or hold thermostat via a
four-pole 25 Amp contactor located inside the
control housing. Only three poles of the
contactor are used, one for each element coil.
The E1100 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 the power from the
thermostat 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 and will
supply power to the heating contactor 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.
