Electric Oven Service Manual

OVEN SYSTEMS
23
3. If coil resistance is correct (585 k
W):
a) Apply line voltage to the unit.
b) Check for 24 VAC at the coil of the
relay when the unit is calling for heat.
c) Check the state of the contacts.
-If the normally open contacts (7 & 4
-or C & NO) are closed and the
-normally closed contacts (7 & 1 or C
-& NC) are open when coil voltage is
-applied, the K4 relay is functioning
-normally.
-If the normally open contacts (7 & 4
-or C & NO) are not closed and/or the
-normally closed contacts (7 & 1 or C
-& NC) are not open when coil voltage
-is applied, the K4 relay is
-malfunctioning and must be replaced.
4. If the coil resistance is incorrect, replace the
K4 relay (page A-14).
RTD
The RTD is a resistance temperature detector
used to detect the cavity temperature.
Testing Procedure
1. Disconnect the RTD from the I/O control
board.
2. Place the RTD in a bowl of ice water for 2
minutes.
3. Take a resistance reading of the RTD.
4. If RTD resistance is not 100
W, RTD is
defective and must be replaced.
NOTE: Use Figure 29, page 24 to determine
resistance readings at temperatures other than
freezing.
Smart Card Reader
The smart card reader allows the oven operator
to load a menu/firmware update from a smart
card. A menu that already exists in the oven can
also be saved to a smart card. For instructions,
see page 15.
Speaker
The speaker is separate from the control board,
and provides audible feedback to the oven oper-
ator whenever a key is pressed or a fault occurs.
Thermostat - 120ºF (Close on Rise)
The cooling fan thermostat actuates the cooling
fans when the temperature in the left end bell
reaches 120ºF (49ºC).
Wire Harness
The wire harness distributes power to the oven’s
electrical components. See page 45 for a
schematic.
The Conveyor System
This section contains information about the
following components, as well as testing
procedures:
- Gear Drive (Conveyor Motor)
- Gear Drive (Conveyor Motor) Speed
Controller (CMSC)
Gear Drive (Conveyor Motor)
The conveyor motor is a 1550 RPM, 3-phase
motor with a built in Hall Effect Sensor. The
speed of the conveyor motor is controlled by the
voltage frequency applied to the windings from
the CMSC. The Hall Effect Sensor sends a DC
pulse back to the control board to verify motor
speed. The control board uses these pulses to
determine the output DC voltage to the
CMSC.
Conveyor ovens with a split-belt configuration
will contain separate gear motors and speed con-
trollers for each belt.
Testing Procedure
1. Disconnect line voltage from the unit.
2. Take a resistance reading of the motor
windings and use Figure 30, page 24 to
verify that the resistance readings are correct.