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Technical Service Manual 43 Revision Dat e: August 2004 CELL FAN ASSEMBLY REMOVE AND REPLACE PROCEDURES CAUTION: BEFORE STARTING ANY MAINTENANCE , DISCONNECT THE OVEN FROM ALL POW ER SOURCES. TOO LS AND MATERIALS REQ UIR…

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.

Technical Service Manual 44 Revision Date: August 2004

BOTTOM CELL MOTOR REMOVAL

If the Oven is belt-only, disconnect the belt at the master link and unthread the belt from the tunnel.

See the procedure for disconnecting the conveyor belt.

2. If the Oven is rail-only, disconnect the conveyor chains at the master links and unthread them from the

tunnel. See the procedure for disconnecting rails and chains.

3. If the Oven has a combination rail/belt conveyor, disconnect and unthread the chains first and then the

belt from the tunnel. See the procedures for disconnecting rails and chains and disconnecting the

conveyor belt.

4. Remove all outer panels to allow access to the underside of the Oven. Remove power from the Oven.

5. Remove the screw(s) holding the thermocouple(s) in place on the cell face. Using a permanent black

marker, circle the hole the thermocouple(s) pass through on the heater face. Carefully straighten the

thermocouple wire and cover it with a piece of 1/8" vinyl tubing. This is to aid relocating the

thermocouple when reassembling the cell.

6. Remove the four Philips style screws holding each ICB in place on the sides of the heater panel.

Remove the ICBs.

7. Remove the three Philips style screws holding the front heater panel bracket. Remove the bracket.

8. Using a hex head wrench, carefully insert the short end into a hole in the heater panel and gently pull

up on the heater panel. Use the 3" putty knife to push the insulation guard clear of the heater panel.

9. Tip the heater panel on its side to gain access to the heater wires on the inside of the cell. Block the

panel in place to remove the heater wires.

10. SKETCH the wire placement on the connections on the heater panel. They will have to be replaced in

the same order.

11. Remove the four wires by using two 11/32" wrenches. Uses one to hold the bottom nut (closest to the

panel) steady, while the other unscrews the top nut to free the wire.

IT IS VERY IMPORTANT TO USE TWO WRENCHES AND HOLD THE BOTTOM NUT STEADY BECAUSE THE

HEATER FOIL IS DIRECTLY ATTACHED TO THE STUD AT THIS LOCATION. THE CERAMIC BLOCKS ARE

FRAGILE AND EASILY BROKEN. IF THE HEATER FOIL TEARS, IT CANNOT BE REPAIRED, AND THE HEATER

PANEL ASSEMBLY MUST BE REPLACED.

12.

Disconnect the thermal switch, then remove the heater panel and set it aside.

13. Remove the blower from the motor shaft. Using a 1/8" hex head wrench, loosen the two setscrews on

the blower enough to remove the blower from the motor shaft. Save the blower to return with the

motor.

14. Go to the rear of the oven and go in under the cell that has the motor to be removed. Document the

locations of the wires in the terminal block. Using a 5/32" hex head wrench or T-handle, carefully

remove the three screws holding the motor in place on the cell.

CAUTION: Hold the motor with one hand while you remove the last screw as the weight of the motor

may cause it to fall on top of you.

15. Remove the Cell Fan motor. You may have to tap on the motor to break it loose from its mount on the

cell.

16. Scrape all RTV off the cell in the motor area. Clean all grease, dirt and RTV from the shaft hole area

and the motor support areas.