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Technical Service Manual 41 Revision Dat e: August 2004 HEATER PLAT E REPLACEMENT CAUTION: BEFORE STARTING ANY MAINTENANCE , DISCONNECT THE OVEN FROM ALL POW ER SOURCES. TO P HEATER REPLACEMENT 1. Locate the defec tive h…

Technical Service Manual 40 Revision Date: August 2004

TEST PROCEDURE FOR HEATER GROUND CONTINUITY

1) Disconnect the main power connection to the oven and disable all heater circuit breakers.

2) Check each line to the respective heater element for a short to ground using an Ohmmeter.

3) The heater element conductors should be completely isolated from ground (i.e. open circuit with reference to ground).

MAXIMUM HEATERS ON

The Oven Control Program limits the maximum number of heaters to be energized at the same time to seven.

MAXIMUM PHASE IMBALANCE

The difference between the maximum loaded phase and the minimum loaded phase is limited to two heaters by the Oven

Control Program. The Oven Control Program limits the number of heaters “ON” at the same time for each phase.

THERMOCOUPLES

All thermocouples in the oven are type 'K', and identified by a red (-) and a yellow (+) wire. Connectors, wires and

terminals must be designated for use with type “K” thermocouples.

TEST PROCEDURE

1) Remove the thermocouple connection block from the front of the AI board in the Oven controller.

2) Measure the resistance of each thermocouple using an Ohmmeter. (All T/Cs have one side connected to ground.For

best results, isolate the T/C being tested)

3) The resistance of a thermocouple wire should be approximately 5 ohms.

4) Test for shorts between the thermocouple wires by disconnecting the thermocouple cable from the plug on the

outside of the cell.

5) Measure the resistance between the two thermocouple wires; it should be open circuit with the connector removed

from the front of the controller.

6) Check for short circuit to ground on both thermocouple wires.

7) Wiring connections must be tight. Verify that all negative thermocouple connections are grounded, along with all

unused thermocouple ports on the front of the controller.

8) Check to determine that one side of the TC probe is NOT common to ground.

Technical Service Manual 41 Revision Date: August 2004

HEATER PLATE REPLACEMENT

CAUTION:

BEFORE STARTING ANY MAINTENANCE, DISCONNECT THE

OVEN FROM ALL POWER SOURCES.

TOP HEATER REPLACEMENT

1. Locate the defective heater.

2. From inside the tunnel, remove the ICB (inter-cell baffles) from either side of the heater cell.

NOTE: DO NOT REMOVE THE BACK ANGLE BRACKET.

3. Note the location of the thermocouple(s) and circle the hole(s) with a permanent marker. Unscrew the bracket holding

the thermocouple in place and gently straighten the thermocouple.

NOTE: DO NOT USE PLIERS TO STRAIGHTEN THE THERMOCOUPLE(S).

4. Remove the angle bracket (at front of top heater plate) ( at front and back on bottom heater plates)

5. Carefully ease the heater plate away from the cell body to expose the wire connections.

6. The terminal blocks are fragile, CAREFULLY disconnect the wires from these blocks. (Using two wrenches (11/32"

open end wrenches 1/8" thick or less), 1 to hold the nut and 1 to turn the screw- (Air Oven Panels only)

7. Disconnect the ground wire.

8. Install the new heater plate following the removal sequence in reverse. Be sure that the thermocouple(s) goes

through the correct hole in the heater plate.

BOTTOM HEATER REPLACEMENT

1. Locate the defective heater.

2. For edge rail systems: remove the top mounting screws from the rails. Remove the chain from the sprockets and

prop the rails out of the way of the heater plate.

3. For mesh conveyor systems: prop the conveyor out of the way of the heater plate and remove the wear rods.

4. Follow instructions 2 to 8 in the TOP HEATER REPLACEMENT instructions above.

TEST PROCEDURE FOR HEATER CONTROL

NOTE: DISABLE ALL HEATER CIRCUIT BREAKERS BEFORE PROCEEDING WITH THE TESTS IN

THIS SECTION.

Ensure that the screws clamping the PCB to the SSRs are all tight. Do not over-tighten as this strips the thread in the

SSR.

Manually activate the heater outputs within the Oven Control Program. NOTE: This operation may require a password.

Check all SSRs by activating them one at a time, and viewing the respective LED.

If an LED does not light, there could be a cable problem, the LED might be faulty or the AI's driver circuits could be faulty.

Technical Service Manual 42 Revision Date: August 2004

CELL FAN MOTORS

Each cell is fitted with a convection motor and fan assembly. The motor is a three-phase, 1/6-hp unit. The motor and fan

assemblies are dynamically balanced to reduce vibration. On some ovens, an inverter is used to control the operating

speed of the motors.

The convection cell motors have a thermal cutout switch installed internally. If the motor exceeds its maximum operating

temperature (155° C), the cutout switch will “open” and the motor will not run. If the cutout is “open”, it will be necessary

to let the motor cool down before attempting to restart it. During normal operations, the motor should not reach

temperatures that cause the cutout to “open”. The upper and lower banks of cell fans are protected by circuit breakers.

The motor supply voltage may be derived from a three Phase step-down transformer. The inputs and outputs of this

transformer are protected by circuit breakers.

TEST PROCEDURE FOR MOTOR RESISTANCE

Þ With power off to the oven, disable the circuit breakers to the motors (top and bottom).

Þ Using an Ohmmeter on its lowest scale, measure the resistance between each phase leg of the motor loads.

Þ Using an Ohm meter check for short to ground (between each phase leg and the motor housing)

The resistance measured between each pair of phase legs should be approximately the same. If the resistance of one

phase leg is significantly different from the other two, either there is a defective motor (short in the windings) or one of the

motors is incorrectly connected.

CELL FAN MOTOR ROTATION CHECK

Create a recipe to activate the cell fans only. Start the recipe and observe the rotation of each motor. During normal

operation, the heat slinger fan turns counter clockwise as viewed from the outside of the cell. If a group of motors (top or

bottom) is not turning in the correct direction, de-activate the cell fan motors via the computer (stop recipe). Shut off

motor circuit breaker (F8) and swap two phase leads at one of the following locations:

- The Load side of K13. (to change rotation of ALL fans), or the load side of F41, F42, F43, F44. (to change rotation of all

Upper or Lower fans), or for an individual Fan Motor rotating backwards, swap any 2 power leads to the Fan Motor at the

Cell terminal Block. (Do NOT move the Green Wire)

VERIFYING CELL FAN SPEED

The system will run the fans at full speed (approx. 3500 RPM). The Output from the controller to the Inverter is +10

VDC. The cell fans will slowly accelerate to full speed.

After the cell fans reach full speed, the true speed of the fans can be measured with a stroboscope. If one or more fans

are NOT between 3400-3600 RPM, then it is likely that either a fan motor or the fan motor wiring is faulty.