MT3255 AND MT3270 SERIES CONVEYOR OVEN SERVICE AND REPAIR MANUAL BLODGETT OVEN COMPANY www.blodgettcorp.com 50 Lakeside Avenue, Box 586, Burlington, Vermont 05402 USA Telephone (802) 658Ć6600 Fax: (802)864Ć0183 PN M8561 Rev B (6/01) 1999 - G.S. Blodgett Corporation All rights reserved. Duplication of the information in this manual is prohibited without the consent of the Blodgett Service Department.
TABLE OF CONTENTS 1. INTRODUCTION Oven Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ventilation Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Gas Specifications . . . . . . . . . . . . . . . . . . . .
TABLE OF CONTENTS Belt Speed Calibration - Closed Loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Belt Speed Calibration - Open Loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Temperature Calibration - United Electric Controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Temperature Calibration - Athena Controller . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CHAPTER 1 INTRODUCTION
MT3255 and MT3270 OVEN SPECIFICATIONS VENTILATION REQUIREMENTS ELECTRICAL SPECIFICATIONS The hood should completely cover the unit with an overhang of at least 6" (15 cm) on all sides not adjaĆ cent to a wall. The distance from the floor to the lower edge of the hood should not exceed 7' (2.1 m). The ventilation system should replace 80% of the exhaust volume with fresh make up air. TABLE 1 should be used as a guideline. NOTE: Three Phase hookup is not permitted on gas models.
INTRODUCTION CE approved installations NOTE: The burner control unit is phase sensitive. If the phase and neutral are switched the control locks out. Connect the oven to a separate group 230V, 50 hz with rigid connection and circuit breaker. The cirĆ cuit breaker should disconnect all poles, including neutral with a contact separation of at least 3 mm. See FIGURE 2. Use 90 C wire and size according to local codes. Connect exhaust fan connector 1 and 2. See FIGURE 2. Connect phase + neutral + ground.
MT3255 and MT3270 GAS SPECIFICATIONS GAS CONNECTIONS GAS REQUIREMENTS Domestic and General Export installations The firing rate for the MT3255 and MT3270 is 150,000 BTU/Hr. (43.9 kW/Hr.) The gas line should be large enough to accommoĆ date the peak demand of all the gas appliances. TABLE 2 reflects a straight line, 50 foot run with no coupling restrictions and no other appliances drawing service. Gas line installations MUST conĆ form to National Fuel Gas Code NFPA 54/ANSI Z223.1 Sec. 1.
INTRODUCTION ILLUSTRATED PARTS LISTS CONVEYOR COMPONENTS NOTE: = ASAP Distributor Required Stocking Parts *ą= Item too large for UPS Ref. Part No. No. Ref. Part No. No. Description Description 21926 Belt, Wire S/S 32" SB (Per Foot) (Total Length MT3270 18 FT, MT3255 16 FT) M2378 Motor, Conv. Drive, Bodine 130V (After 9/90) 23112 Belt, Wire S/S 15.75" TB (Per Foot) (Total Length MT3270 18 FT, MT3255 16 FT) M2500 Brush Set, Bodine 21152 Chain, Drive Single Belt (2.
MT3255 and MT3270 TEMPERATURE CONTROLS NOTE: = ASAP Distributor Required Stocking Parts COMPUTER CONTROLS Ref. Part No. No. M6474 Ref. Part No. No.
INTRODUCTION ELECTRICAL COMPONENTS NOTE: = ASAP Distributor Required Stocking Parts Ref. Part No. No. Ref. Part No. No.
MT3255 and MT3270 GAS BURNER COMPONENTS NOTE: = ASAP Distributor Required Stocking Parts Ref. Part No. No. Ref. Part No. No. Description Description 22132 Burner Assy.
INTRODUCTION EXTERIOR COMPONENTS NOTE: = Doors are not returnable Ref. Part No. No. Ref. Part No. No.
MT3255 and MT3270 EXCLUSIVE TO EXPORT 50 HZ NOTE: = ASAP Distributor Required Stocking Parts Ref. Part No. No. Ref. Part No. No. Description Description M2245 Valve, Solenoid M7334 M2276 Burner Assy., Complete (SpeciĆ fy Gas Type) Pilot Burner & Ignitor Assy., Natural (CE) M3237 Burner Assy. (CE) M0706 Orifice, Main Burner (Specify MTD) M2497 Switch, Push Button (CE) M4597 Motor & Blower Assy., CW M2498 Switch, Contact (CE) M4598 Motor & Blower Assy.
INTRODUCTION MT3255E GENERAL EXPORT CONTROL BOX (Control Plate not shown) 1-10
MT3255 and MT3270 MT3255G AND MT3270 DOMESTIC & GENERAL EXPORT CONTROL BOX (Control Plate and/or Gas Burner Components not Shown) 1-11
INTRODUCTION MT3255 AND MT3270 CE CONTROL BOX (Control Plate and/or Gas Burner Components not Shown) 1-12
MT3255 and MT3270 MT3255 AND MT3270 DOMESTIC GAS BURNER COMĆ PONENTS (Control Box not Shown) 1-13
INTRODUCTION MT3255 AND MT3270 CE GAS BURNER COMPONENTS (Control Box not Shown) 1-14
MT3255 and MT3270 MT3255 AND MT3270 DOMESTIC & GENERAL EXPORT SB CONTROL PLATE ASSY 1-15
INTRODUCTION MT3255 AND MT3270 CE SB CONTROL PLATE ASSY 1-16
MT3255 and MT3270 MT3255 AND MT3270 EXTERIOR OVEN VIEW 1-17
CHAPTER 2 ASSEMBLY
MT3255 and MT3270 OVEN ASSEMBLY PROCEDURES RETURN AIR DIVERTERS CONVEYOR BELT SUPPORTS 1. Slide the return air diverters into the oven. The edge of the diverter should be 3" (7.6 cm) from the outside edge of the oven cavity. 1. Slide the left conveyor belt support (with the sprocket on the end of the shaft) into the supĆ port tracks. The sprocket must be located inĆ side the control panel after being pushed into the oven. 2. Fasten the 1/4Ć20 hex head screw from the control box into the belt support. 3.
ASSEMBLY Unless otherwise specified, the conveyor travel is factory set for leftĆtoĆright operation when facing the drop down door. If a direction change is reĆ quired, the polarity of the drive motor must be reĆ versed. To change the polarity of the drive motor, disconnect the oven from the power source and inĆ terchange the black and white motor leads at the D.C. Controller Board located within the control box.
MT3255 and MT3270 DRIVE CHAIN END PLUGS 1. Install the drive chain around the drive motor and then around the sprocket on the conveyor belt support. 1. Install the upper and lower end plugs at both ends of the oven. 2. Push the conveyor motor back to tighten the drive chain. CRUMB PANS 1. Install the crumb pans under each end of the conveyor. 3.
CHAPTER 3 OPERATION
MT3255 and MT3270 STANDARD CONTROL OPTIONS U.E. TEMPERATURE CONTROLLER WITH OPEN LOOP DC DRIVE SYSTEM 1 2 3 4 5 ON 6 OFF HEAT ON OFF BLOWER COOK TIME ON OFF 7 TEMPERATURE CONVEYOR FIGURE 1 CONTROL DESCRIPTION NOTE: If the oven fails to ignite after the thirty (30) second purge, turn the HEAT SWITCH (5) to OFF and wait 5 minutes before turning back to ON. 1. COOK TIME DISPLAY - Displays the belt speed. 2. CONVEYOR ADJUSTMENT KNOB - Turn to adjust the conveyor speed. 3.
OPERATION U.E. TEMPERATURE CONTROLLER WITH CLOSED LOOP DC DRIVE SYSTEM 1 2 3 4 5 ON 6 OFF HEAT ON OFF BLOWER COOK TIME ON OFF 7 TEMPERATURE CONVEYOR FIGURE 2 CONTROL DESCRIPTION burner. Initial start may require longer due to air in the gas line. 1. COOK TIME DISPLAY - Displays the belt speed. 2. CONVEYOR ADJUSTMENT KEYS - Press to adjust the conveyor speed. 3. TEMPERATURE CONTROL KNOB - Turn to set cook temperature. 4. HEAT LIGHT - Indicates the control is calling for heat. 5.
MT3255 and MT3270 ATHENA TEMPERATURE CONTROLLER WITH OPEN LOOP DC DRIVE SYSTEM 1 2 3 4 5 6 7 8 ON 9 OFF HEAT COOK TIME ON OFF 10 ACTUAL SETPOINT ON OFF BLOWER HEAT TEMPERATURE CONVEYOR FIGURE 3 CONTROL DESCRIPTION NOTE: If the oven fails to ignite after the thirty (30) second purge, turn the blower switch OFF and wait 5 minutes before turning back ON. 1. COOK TIME DISPLAY - Gives the belt speed. 2. CONVEYOR ADJUSTMENT KNOB - Turn to adjust the conveyor speed. 3.
OPERATION ATHENA TEMPERATURE CONTROLLER WITH CLOSED LOOP DC DRIVE SYSTEM 1 2 3 4 5 6 7 8 ON COOK TIME ON OFF 10 9 OFF HEAT ACTUAL SETPOINT ON OFF BLOWER HEAT TEMPERATURE CONVEYOR FIGURE 4 CONTROL DESCRIPTION 4. Turn the HEAT SWITCH (8) to ON. NOTE: If the oven fails to ignite after the thirty (30) second purge, turn the blower switch OFF and wait 5 minutes before turning back ON. 1. COOK TIME DISPLAY - Gives the belt speed. 2.
MT3255 and MT3270 COMPUTER CONTROLLER 1 2 9 3 8 7 6 5 4 FIGURE 5 CONTROL DESCRIPTION CONTROL OPERATION 1. DIGITAL DISPLAY - Displays the time, temĆ perature and controller related information. To turn the oven on: 1. Press and hold the ON/OFF key (2). The disĆ play reads OFF when the oven is idle. 2. The display flashes WAIT LOW SET TIME. 3. The FAN and HEAT status lamps (9) light. The fans begin to run. The heat rises to the proĆ grammed temperature.
OPERATION PROGRAMMING PROCEDURES DISPLAY INFORMATION Programming the Cook Time: WAIT LOW - indicates that the present oven temperature is lower than the set point temperĆ ature. When the oven reaches the set point temperature the display changes to READY. READY - indicates that the oven is ready to acĆ cept product. SET TEMP mmss - indicates the current cook time setting. HIGH TIME - indicates that the temperature is well above the set point.
MT3255 and MT3270 SEQUENCE OF OPERATION NOTE: The following instructions represent the most common configurations. For questions regarding othĆ er options call the Blodgett Service Department at (800)331Ć5842. MTĆ70ĆPH DOMESTIC - M2468 REV E OPERATION NOTE: The following is also applicable to the MT3255 with 3 blower motors. 1. Turn the blower switch (1) to ON. The N.O. conĆ tacts close, the N.C. contacts open.
OPERATION nal of a SPDT thermal switch (9). The switch toggles if the temperature passing its face exĆ ceeds the rating on the back of the switch. 6. The conveyor is driven by an open loop D.C. control system consisting of a conveyor switch (23), time display (26), 10kW potentiometer (24), D.C. speed control board (28), 130 VDC motor (27) and #10 Hall effect pickup (25). ReĆ fer to page 5-1 for pickup troubleshooting. AfĆ ter the conveyor switch is turned on, the time display illuminates. The D.C.
MT3255 and MT3270 MTĆ70ĆPH GENERAL EXPORT - M2501 REV D OPERATION NOTE: The following is also applicable to the MT3255 with 3 blower motors. 1. Turn the blower switch (1) to ON. The N.O. conĆ tacts close, the N.C. contacts open. 220 or 240 VAC runs to terminal #3 of the temperature controller (2), both coils of the motor contacĆ tors (4) and terminal #7 of the hi/lo limit board (7). Terminal #7 is an output.
OPERATION NOTE: The switch is located in the front conĆ trol compartment. It protects the other components from hi ambient heat. If this switch is cold, it should be made beĆ tween common and N.C. terminals sending power to the single solenoid gas valve (10). 4. When power is applied to the coils of both moĆ tor contactors (4) the contacts close sending power to the four convection fans (5) located in the back of the oven. Power is also applied to the coil of the SPST relay (3).
MT3255 and MT3270 MT3270 WITH STANDARD CONTROLS - 21575 REV E NOTE: The following is also applicable to the MT3255 with 3 blower motors. COMPONENT REFERENCE NOTE: Refer to FIGURE 8 page 3-23 for compoĆ nent locations. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25.
OPERATION NOTE: The switch is located in the front conĆ trol compartment. It protects the other components from hi ambient heat. If this switch is cold, it should be closed sendĆ ing power to the single solenoid gas valve (17). 4. When power is applied to the coils of both moĆ tor contactors (3) the contacts close sending power to the four convection fans (6) located in the back of the oven. 5. The oven has six cooling fans (18). Two on the front control panel keep the panel below 140 F (60 C).
MT3255 and MT3270 MT3270 TWIN BELT WITH REMOTE CONTROLS - M4410 REV A COMPONENT REFERENCE OPERATION NOTE: Refer to FIGURE 9 page 3-24 for compoĆ nent locations. 1. Apply power to the oven. Program the time and temperature into the computer (1). The burner valve relay (4), blower relay (2) and main conĆ trol relay (3) energize powering up the oven. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22.
OPERATION face exceeds the rating on the back of the switch and may start the fans even if the oven is off. If this switch is cold, it should be made between common and N.C. terminals sending power to the cooling fans (18). board or the time programmed into the comĆ puter. NOTE: The DAC receives 20 VDC from the speed control boards. The DAC reĆ turns a portion of the voltage (between .47 and 4.7 VDC). The amount of voltĆ age is dependent on the time proĆ grammed into the computer.
MT3255 and MT3270 MT3270 WITH CLOSED LOOP - M4206 REV B NOTE: The following is also applicable to the MT3255 with 3 blower motors. COMPONENT REFERENCE NOTE: Refer to FIGURE 10 page 3-25 for compoĆ nent locations. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23.
OPERATION NOTE: The switch is located in the front conĆ trol compartment. It protects the other components from hi ambient heat. If this switch is cold, it should be closed sendĆ ing power to the single solenoid gas valve (17). 4. When power is applied to the coils of both moĆ tor contactors (3) the contacts close sending power to the four convection fans (5) located in the back of the oven. 6. The conveyor belt is driven by a closed loop D.C.
MT3255 and MT3270 MT3255E - M4289 REV B COMPONENT REFERENCE OPERATION NOTE: Refer to FIGURE 11 page 3-26 for compoĆ nent locations. 1. Turn the blower switch (1) to ON. The N.O. conĆ tacts close, the N.C. contacts open. 115 VAC runs to L1 of the temperature controller (2), both coils of the motor contactors (3) and terĆ minal #7 of the hi/lo limit board (4). Terminal #7 is an output.
OPERATION switch and may start the fans even if the oven is off. If this switch is cold, it should be made between common and N.C. terminals sending power to the cooling fans. the time programmed into the digital time disĆ play. To slow the belt down, press the down arĆ row key. To increase belt speed, press the up arrow key. NOTE: The switch is located on the ceiling of the convection fan compartment. NOTE: When this component is replaced it must be reprogrammed for the apĆ propriate tunnel length.
MT3255 and MT3270 MT3270 CE - M8296 REV A NOTE: The following is also applicable to the MT3255 with 3 blower motors. COMPONENT REFERENCE NOTE: Refer to FIGURE 12 page 3-27 for compoĆ nent locations. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32.
OPERATION er times out, power goes to the coil of a SPST relay (14), allowing its contacts to close. overheating. The cooling fans start when the motor contactor powers up and closes beĆ tween terminals #3 and #4. Power goes to the N.C. terminal of a SPDT thermal switch (22). The switch toggles if the temperature passing its face exceeds the rating on the back of the switch and may start the fans even if the oven is off. If this switch is cold, it should be made between common and N.C.
FIGURE 6 3-21 28 26 20 25 27 20 20 29 22 23 20 30 19 21 20 24 20 4A 2 1 8 4B 16 3 5 7 9 5 17 18 5 10 5 15 11 12 14 13 6 MT3255 and MT3270
3-22 27 25 26 FIGURE 7 19 19 19 28 19 24 21 22 29 20 18 19 23 19 4A 1 2 8 4B 15 5 7 9 5 3 16 17 10 5 5 11 12 14 13 6 OPERATION
FIGURE 8 3-23 18 25 24 22 21 18 18 23 18 19 20 18 18 3B 2 1 7 3B 13 5 6 16 6 14 15 17 6 12 6 9 10 8 11 4 MT3255 and MT3270
1 18 18 18 18 21 4 19 22 3 2 16 20 5B 13 5A 19 17 6 17 17 14 15 8 7 17 12 9 11 10 OPERATION FIGURE 9 3-24
20 17 17 22 17 21 17 18 19 17 17 3A 2 1 6 3B 12 4 5 15 5 16 5 5 11 8 9 7 10 MT3255 and MT3270 FIGURE 10 3-25
16 11 14 11 15 11 11 12 11 13 11 3A 2 1 7 3B 4 8 5 5 5 9 10 6 OPERATION FIGURE 11 3-26
3-27 27 28 24 21 25 21 21 26 33 21 22 31 32 30 23 21 21 2 8 3 1 5 20 6 16 17 6 19 15 18 9 FIGURE 12 6 4 6 11 10 14 12 13 7 MT3255 and MT3270
OPERATION OVEN ADJUSTMENTS FOR COOKING TEMPERATURE The internal temperature of your product is very imĆ portant; and should be taken as soon as the prodĆ uct completely exits the cooking chamber. This reading will give a general indication of whether or not the product is fully cooked. A multiple topping pizza, for example, will be cooked if the internal temperature is over 160Ć165 F (64Ć67 C). For a single topping, such as cheese, the temperature should be greater than 170Ć180 F (69Ć74 C).
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CHAPTER 4 CALIBRATION AND ADJUSTMENT
MT3255 and MT3270 CONVECTION BLOWER MOTORS TO CHECK MOTOR ROTATION TO CHECK LOWĆLIMIT 1. Remove the back of the oven body and verify proper motor rotation. (See FIGURE 1) 1. Turn the oven on and let it heat up to approxiĆ mately 200 F (93 C). For motor placement, the direction of rotation is viewed left to right from the oven's rear. Typically the motor direction is referenced to the end of the shaft (EOS).
CALIBRATION AND ADJUSTMENT REGULATED GAS PRESSURE 1. Let the oven run up to 510 F (266 C). You may now verify the operational and regulated gas pressures. If pressure adjustments are needed, turn the adĆ justing screw located under a screw cap of the dual regulated valve. Adjust the gas pressure by turning the screw clockwise to raise the gas pressure and counterĆclockwise to lower the gas pressure.
MT3255 and MT3270 STANDARD CONTROLLER CONFIGURATION BELT SPEED CALIBRATION - CLOSED LOOP DART MICRODRIVE MDP 1. Remove the top cover from the unit. The interĆ nal dip switch is located next to the transformĆ er. See FIGURE 4.
CALIBRATION AND ADJUSTMENT FIELD PROGRAMMING MDP CONTROLS Program Minimum Setting While in Programming Modes, set decimal place/ mode variable to the proper position (0 thru 4 = Rate 5 = Time). This allows settings to be made in the proper units. Only set the variables that you wish to change. You can change any variable WITHOUT having to reset the others. 1. Flip DIP switch 2 (Program Minimum Setting) ON. 2. Present value for Lower Limit will appear in the display. 3. Use Up and Down buttons to change.
MT3255 and MT3270 BELT SPEED CALIBRATION - OPEN LOOP NOTE: The following procedures must be perĆ formed after dc voltage levels have been set and are known to be accurate. Set The Belt Speed DIP Switches. Set the DIP switches using the data from the table below. The cooking time digital display should be adĆ justed when changing any of the system compoĆ nents. Prior to adjusting the display, determine the following two specifications: Pickup DIP Switch Setting MT3255 - 60 Hz Motors 1.
CALIBRATION AND ADJUSTMENT TEMPERATURE CALIBRATION - UNITED ELECTRIC CONTROLLER NOTE: Th U.E. and Zytron boards get input from eiĆ ther single or dual lead thermocouples. lowers the display reading and raises the temĆ perature. A counterĆclockwise rotation raises the reading and decreases the temperature. Check the oven set point. Adjustment of the potentiometer may affect this reading. Bring the oven up to 525 F (274 C). Verify the caliĆ bration. LOW LIMIT ADJUSTMENT 1. Bring the oven to 200 F (93 C). 2.
MT3255 and MT3270 TEMPERATURE CALIBRATION - ATHENA CONTROLLER THE CONFIGURATION MENUS Setting the Deviation Band Alarm 1. Press and hold the actual temperature key for approximately 10 seconds. When the menu system has been accessed, the display toggles between and either or . The deviation band alarm causes the display to flash when the actual temperature varies (in either direction) from the setpoint. The deviation band alarm is adjustable to off or values from 1 F to 252 F (1 C to 740 C).
CALIBRATION AND ADJUSTMENT the setting, counterĆclockwise decreases it. See FIGURE 8. the heat circuit. This enables the oven to heat above the highest temperature allowed by the controller. HIGH LIMIT ADJUSTMENT 2. When the display reads 600 F (316 C), the burner blower motor should shut off. If the temĆ perature rises above 600 F (316 C), adjust the hiĆlimit pot (FIGURE 8) so the burner shuts off at 600 F (316 C).
MT3255 and MT3270 COMPUTER CONTROLLER CONFIGURATION COMPUTER CONTROLS INITIATING ACCESS MODE CONFIGURATION The Cooking Computer provides a special Access Mode for setting and displaying certain computer special functions. To initiate the Access Mode place the control in the OFF state, (OFF is shown in the display when power is first applied to the control). Press the following sequence of keys to set the control to Access Mode: CLEAR 1 2 3 4 5 6 ENTER. The display reads ACCESS.
CALIBRATION AND ADJUSTMENT Boost Option - (versions 2.00 or 3.00) When the controller is in the ACCESS" mode, press the following buttons: CLEAR 2 1 2 ENTER to enter the boost option. DISPLAY BOOST / MODEĆ? (Flash alternately) ACTION TAKEN Press PROG ENTER DISPLAY OPTĆ1 OPTĆ2 ACTION TAKEN or Press any numeric key to toggle between OPTĆ1 and OPTĆ2 Select OPTĆ1 to turn off boost mode.
MT3255 and MT3270 TEMPERATURE CALIBRATION TO ENTER THE CALIBRATION MODE 1. Press the ON/OFF key until OFF is displayed. 1. Press PROG/ENTER followed by ACT_TEMP. The display flashes either POS * OFFSET or NEG * OFFSET 2. Press CLEAR 1 2 3 4 5 6 ENTER to enter the access mode. The display reads ACCESS. NOTE: POS OFFSET is displayed if a value has been programmed in for a positive offĆ set. NEG OFFSET is displayed if a valĆ ue has been programmed for a negaĆ tive offset.
CALIBRATION AND ADJUSTMENT BELT SPEED CALIBRATION To enter the calibration mode: The belt will travel very slowly during this part of the calibration procedure. To minimize the time spent on STEP-2, measure off 10" on the conveyor support. Place an object on the belt and note the travel time for the 10" measured distance. 1. Press the ON/OFF key until OFF is displayed. 2. Press CLEAR FRONT BELT, FRONT BELT, FRONT BELT, PROG/ENTER to enter the AcĆ cess mode. The display flashes ACCESS. 3.
MT3255 and MT3270 MOTOR CONTROL BOARD ADJUSTMENT NOTE: This procedure does not apply to Dart MiĆ crodrive systems. High/low speed motor control board adjustĆ ment for 180 and 130 volt DC motors NOTE: The motor control board is located on the slide out control panel. High Speed Motor Adjustment: Follow Belt Speed Calibration through STEP 2 (see page 4-12). 1.
CALIBRATION AND ADJUSTMENT Minimum Speed Torque (current) limiting adjustment (DO NOT ADJUST) Maximum Speed Acceleration Adjustment Switches 2,4,5,6,7 ACC Yellow or Violet (pin 12) Orange or Gray (pin 10) Line Fuse ON DIP Switch on early models only TP2 Socket J1 Blue Gray TORQ MIN TP1 Test Points Blue (pin 8) Violet MAX REG Regulation Adjustment Armature Fuse FL TB1 Speed Pot L N A1 NOTE: Colors may vary between early ovens.
MT3255 and MT3270 RERATING THE APPLIANCE Due to the lack of oxygen at higher elevations, the unit may need to be rerated. (The orifice size may need to be adjusted to accommodate different air pressures at higher elevations.) If not rerated, inĆ complete combustion may occur releasing AldeĆ hydes and CO or Carbon Monoxide. Any of these are unacceptable and may be hazardous to the health of the operator. To choose the correct orifice for different altitudes several factors must be known: 1.
CALIBRATION AND ADJUSTMENT CHECKING THE FIRING RATE Locate the time observed in STEP 2. Move across the table to either the 1/2 cu. ft. or the 2 cu. ft. column to find the gas input to the burner. Method #1 1. Turn off all other appliances on the line. Turn on the appliance to be measured. 2. Using either the 1/2 cu. ft. or the 2 cu. ft. dials located on the gas meter, note the time it takes the indicator to complete one revolution. See FIGURE 10. 2 3 3.
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CHAPTER 5 TROUBLESHOOTING
MT3255 and MT3270 DC DRIVE SYSTEM POSSIBLE CAUSE(S) SUGGESTED REMEDY Symptom #1 - Belt does not move (standard controls) Conveyor switch is turned off. Turn switch to on. Armature fuse on Bodine board is blown. Ohm this fuse out to determine if blown. If necesĆ sary, replace with 250 milliamp fuse. Determine the amp draw of the motor. Line fuse on Bodine board is blown. Replace with 5 amp fuse. DC motor is leaking oil. Replace motor. Motor ohms out higher then 162W.
TROUBLESHOOTING POSSIBLE CAUSE(S) SUGGESTED REMEDY Symptom #3 - Belt does not move (computer controls) Oven in OFF mode. Turn to ON position. Loose computer controller cord connection. Adjust and retighten cables and set screws. Time not programmed into computer. Program in a cook time. See Operation Section (page 3-6). Emergency stop switch on OFF. Pull switch out to ON. Control circuit breaker tripped. Reset breaker. Belt hooked on something in oven.
MT3255 and MT3270 CONVECTION SYSTEM POSSIBLE CAUSE(S) SUGGESTED REMEDY Symptom #1 - Blower motor(s) not running Blower switch off. Turn switch to on position. No power to the oven. Verify power to the oven. If there is no power deĆ termine cause. Motor fuse blown. Replace fuse. Determine the amp draw. Faulty start capacitor. Replace capacitor. Motor burned out. Check draw (3 amps or greater). Thermal overload tripped.
TROUBLESHOOTING HEATING SYSTEM POSSIBLE CAUSE(S) SUGGESTED REMEDY Symptom #1 - Burner will not fire (standard controls) Oven in off mode. Turn the oven on. No power to the oven. Determine if the circuit breaker is tripped. Fuse blown on the control panel. Replace the fuse. Determine if the controller setpoint is above actuĆ al. If the setpoint is not above the actual, reset acĆ cordingly. Intermittent Ignition Device (IID) system locked out.
MT3255 and MT3270 POSSIBLE CAUSE(S) SUGGESTED REMEDY Symptom #2 - Burner will not fire (computer controls) Oven in OFF mode. Turn to ON position. Emergency stop switch on OFF. Pull switch out to ON. Control circuit breaker tripped. Reset breaker. Combustion motor not running. Check transformer for primary and secondary voltage. Check main control and burner valve relays to see if closed. Check relay in combustion burner box. If bad reĆ place relay.
TROUBLESHOOTING COMPUTER CONTROL SYSTEM POSSIBLE CAUSE(S) SUGGESTED REMEDY Symptom #1 - Computer controller displays: PROBE Ć OPEN Ć PROBE Ć SHORT and alarm buzzer sounds Internal problem with computer controller. Verify display integ. in the 2nd level programĆ ming. If the controller has been programmed the computer may need to be replaced. Loose connections at computer controller. Tighten connections. Shorted or open RTD probe.
MT3255 and MT3270 Symptom #4 - Burner operates sporadically Air pressure switch may be open. Check convection blower (or 4 convection fans) for proper operation. Thermal switch tripped. Determine the ambient temperature in the conĆ trol compartment. If above 140 F (60 C) check the cooling fan operation. Faulty RTD probe. Use the chart in the Technical Appendix (page 6-4) to determine if probe is bad. Replace if necĆ essary. Excessive food/debris accumulation blocking the airflow.
CHAPTER 6 TECHNICAL APPENDIX
MT3255 and MT3270 INTERMITTENT IGNITION SYSTEM PRINCIPLES OF OPERATION In the IID system the probes exposed to the pilot flame are the Flame Sensor and the Pilot Burner Hood. Since the surface area of the pilot hood is larger than the flame sensor, the current rectificaĆ tion process takes place. Current is conducted from terminal 4 at the control through the flame sensor cable to the flame sensor.
TECHNICAL APPENDIX SERVICE PROCEDURES To Measure DC Flame Sensing Current: Service the IID system as follows: 1. Turn off the power supply to the ignition conĆ trol. 1. Make certain the thermostat contacts are open. 2. Disconnect the flame sensor cable from termiĆ nal #4 on Johnson units or terminal #15 on Landis & Gyr units. 2. Check for proper supply voltage at primary and secondary of system transformer. 3. Set the selector switch on the meter to microĆ amp scale.
MT3255 and MT3270 5. Install the Y75 sensing probe into the pilot burner. Reconnect the sensing probe cable. The connections to the sensing probe and control terminal must be secure. REPAIRING THE ELECTRONIC IGNITION SYSTEM Flame Sensing Current Maintenance: The flame sensor is made of carbon steel and subĆ ject to contamination and oxidation buildup. Any buildup on the sensor can add enough resistance to drop the signal below the required minimum. Carbon and oxidation can also build up on the pilot hood.
TECHNICAL APPENDIX COOKING COMPUTER - TEMPERATURE VS RESISTANCE T/F Res/Ohms T/F Res/Ohms T/F Res/Ohms T/F Res/Ohms 70 541.12 230 711.43 390 877.15 550 1038.293 75 546.51 235 716.68 395 882.26 555 1043.255 80 551.9 240 721.92 400 887.36 560 1048.212 85 557.28 245 727.16 405 892.46 565 1053.165 90 562.66 250 732.4 410 897.55 570 1058.113 95 568.04 255 737.63 415 902.63 575 1063.057 100 573.4 260 742.85 420 907.72 580 1067.997 105 578.
MT3255 and MT3270 THERMOELECTRIC VOLTAGE IN ABSOLUTER MILLIVOLTS TYPE J THERMOCOUPLE F Reading +5 F F Reading +5 F 10 -0.611 -0.473 360 9.790 9.944 20 -0.334 -0.195 370 10.098 10.252 30 -0.056 0.084 380 10.407 10.561 40 0.224 0.365 390 10.715 10.869 50 0.507 0.648 400 11.023 11.177 60 0.791 0.933 410 11.332 11.486 70 1.076 1.220 420 11.640 11.794 80 1.363 1.507 430 11.949 12.103 90 1.652 1.797 440 12.257 12.411 100 1.942 2.088 450 12.566 12.
TECHNICAL APPENDIX CONVERSION FACTORS COMMON CONVERSION FACTORS PRESSURE CONVERSIONS FACTORS Multiply By To Get Multiply By To Get BTU/hr .001054804 MJ/hr in/H2O 0.0361 P.S.I. .0002931 kW 25.41 mm/H2O .29285 W 1.868 mm/Hg .0372589 MJ/m3 .0025 kg/cm 2 8.905102 kcal/m 3 .0025 bar MJ/hr 948.0434279 BTU/hr 2.489 mbar Mj/m 3 26,839225 BTU/ft 3 248.9 Pa kW 3414.71732 BTU/hr .2489 kPa ft3 .02832 m3 27.71 in. H2O ft2 .09290304 m2 2.036 in. Hg inches 25.
MT3255 and MT3270 PRESSURE CONVERSION PRESSURE CONVERSION CHART in/H2O P.S.I in/Hg mm/H2O mm/Hg kg/cm2 bar mbar Pa kPa 1 .0361 .0735 25.41 1.868 .0025 .0025 2.489 248.9 .2489 2 .0722 .1470 50.81 3.736 .0051 .0050 4.978 497.8 .4978 3 .1083 .2205 76.22 5.604 .0076 .0075 7.467 746.7 .7467 4 .1444 .2940 101.62 7.472 .0102 .0099 9.956 995.6 .9956 5 .1804 .3673 127.0 9.335 .0127 .0124 12.44 1244 1.244 6 .2165 .4408 152.4 11.203 .0152 .0149 14.
TECHNICAL APPENDIX in/H2O P.S.I in/Hg mm/H2O mm/Hg 28 1.010 2.056 710.8 52.26 29 1.047 2.132 736.8 30 1.083 2.205 31 1.119 32 kg/cm2 bar mbar Pa kPa .0710 .0696 69.64 6964 6.964 54.18 .0736 .0722 72.19 7219 7.219 762.2 56.04 .0761 .0747 74.67 7467 7.467 2.278 787.5 57.91 .0787 .0772 77.15 7715 7.715 1.155 2.352 812.8 59.77 .0812 .0796 79.63 7963 7.963 33 1.191 2.425 838.2 61.63 .0837 .0821 82.12 8212 8.212 34 1.227 2.498 863.5 63.
