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Technical Service Manual 42 Revision Dat e: August 2004 CELL FAN MOTORS Each cell is f itted with a convection m otor and f an assem bly. The m otor is a three-phas e, 1/6-hp unit. T he m otor and fan assem blies ar e dy…

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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.
Technical Service Manual 43 Revision Date: August 2004
CELL FAN ASSEMBLY REMOVE AND REPLACE PROCEDURES
CAUTION:
BEFORE STARTING ANY MAINTENANCE, DISCONNECT THE
OVEN FROM ALL POWER SOURCES.
TOOLS AND MATERIALS REQUIRED:
RTV SS986 silicone sealer.
Cleaning solvent or Isopropyl alcohol.
Clean rags.
Putty knifes 3" wide & 1" wide.
Razor scrapers.
1/8" tip, 4" long, flat bladed screwdriver.
#2 cross head, 8-10" long, screwdriver.
1/8" hex key T-handle or 1/8" hex key bit for impact wrench.
5/32" hex key T-handle or 5/32" hex key bit for impact wrench.
Impact wrench.
Torque wrench calibrated in inch pounds with a range exceeding 50 inch pounds (click type).
(2) 11/32" open end wrenches 1/8" or less in thickness.
.090" Fan mounting gauge.
A 10" 4x4 block of wood
1/8” tubing
Paper and pencil.
Make a clear sketch of the Inter Cell Baffle (ICB) settings for all cells. The ICBs will be removed and replaced
during this procedure.
1 Remove the oven sheet metal skin(s) to gain access to the cell fans.
2 At the front of the Oven open the Hood with the hood up switch. Make sure that the 'hood' is in the
fully open position. NOTE: watch the overhead clearance and exhaust duct movement while raising
the Hood.
Motors and Fans MUST NOT be separated or mixed up, be sure to match up the serial numbers on both
components. The motor/ fan units are dynamically balanced and MUST remain together.