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Convection Circuit
8 - 3
CONVECTION ELEMENT AND
THERMOCOUPLES
The convection element (See Figure 8-1) is
located in the rear back on the left side of the
oven. It is controlled by one or two solid-state
relays (K5 and K7), depending on model, located
in the top, center of the control compartment of
the oven. Each relay coil operates on 24VDC
which is supplied from the I/O control circuit
assembly. The temperature is referenced by two
“K” type thermocouples.
• The HX thermocouple is in the rear of the
oven by the catalytic converter.
• The CC thermocouple is located on the top
left side of the oven near the front by the
door.
How To Turn Heaters ON and OFF
1) Press the BACK key until oven displays says
OVEN OFF.
2) From the OVEN OFF screen Press the BACK
& ENTER keys simultaneously and key in Pin
number 9-4-2-8 then ENTER.
3) Press the HEATER key and verify that status
indicators h and H go from the highlighted
position h H to the un-highlighted position
(this indicates the heater circuit is energized).
On the C3/AB and C3/C, only, one of the heater
wires to the hot air element is looped through
an inductance coil transformer on the I/O
control circuit assembly. It must draw a
minimum current of 7.5 amps to satisfy the
circuit. If it does not, the “H” status character
on the Test Mode display will be a reversed
character H.
4) Depress the HEATER key again and the
heaters will turn off. Again this is indicated by
the status indicators at the bottom of the
screen h H.
Status Indicators with HEATERS in the OFF
mode:
P – S – M– t – h – H – A – W
Status Indicators with HEATERS in the ON
mode:
P – S – M– t – h – H – A – W
Notes:
In order for the heaters to energize the blower
motor must be operational, usually indicated
by status indicator A always un-highlighted.
IMPORTANT HEATER DISCUSSION
The C series oven uses either an open coil or
sheathed heater. The open coil element is
obsolete, but may still be found in C3/AB ovens
and C3/C ovens. This heater is susceptible to
cleaners not approved by TurboChef. If this
heater fails, it should be replaced by the newer
sheathed heater (See Figure 8-3).
The sheathed heater consists of two individual
heating elements encased within one sheath;
therefore, when replacing the single–phase open
coil heater with this unit on the C3/AB or C3/C
you must wire the individual heaters in parallel
When wired correctly the total resistance should
be 12 ohms @ 240VAC (20 Amp draw). At 208
VAC the total resistance should be 9 ohms (23
amps draw).
Changing Heater Operating Voltage
All C3/C factory ovens are equipped with a
208VAC rating heater and set to operate at
208VAC, unless specified. If voltage supplied to
oven is 240VAC then change oven setup by
following the steps below:
1) Press and hold the BACK & ENTER keys
simultaneously and then key in 8-6-5-8 (VOLT).
2) Press the number 4 to set the oven at 240
then press the number 8 to select the heater
rating of 208VAC. A small H will appear next to
the OVEN OFF screen.
3. Change wiring on filament transformer to
represent supplied voltage.
Pins 1 & 2= 200VAC-208VAC
Pins 1 & 3= 240VAC
Replace the thermocouple as follows:
1. Make a note where the old thermocouple
exited the compression fitting.
2. Measure the distance from the exit point to
the end of the thermocouple.
3. Mark this distance on your new thermocouple
with a marker or a piece of tape.
4. Install the new thermocouple