Blodgett MT3870 Installation and operating manual

MT3870
CONVEYOR OVEN
SERVICE AND REPAIR MANUAL
BLODGETT OVEN COMPANY
www.blodgettcorp.com
50 Lakeside Avenue, Box 586, Burlington, ermont 05402 USA Telephone (802) 658Ć6600 Fax: (802)864Ć0183
PN M7489 Rev B (6/01)
 1996 - 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
i
1. INTRODUCTION
Oven Specifications 1-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
entilation Requirements 1-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Electrical Specifications 1-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Gas Specifications 1-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Illustrated Parts Lists 1-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2. ASSEMBLY
Oven Assembly Procedures 2-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Return Air Diverters 2-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Air Nozzles 2-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Conveyor Rack Assemblies 2-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wire Conveyor Belt 2-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Drive Chain 2-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Air Plates 2-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
End Plugs 2-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Conveyor Belt Tensioners 2-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Crumb Pans 2-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Mount Remote Control 2-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
False Front (If Applicable) 2-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3. OPERATION
Computer Controller 3-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Control Description 3-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Control Operation 3-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Programming Procedures 3-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Display Information 3-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Sequence of Operation 3-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Domestic and General Export Ovens 3-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CE Ovens 3-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Oven Adjustments for Cooking 3-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Temperature 3-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Conveyor Speed Time vs. Temperature 3-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Air Flow Adjustments 3-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4. CALIBRATION AND ADJUSTMENT
Convection Blower Motors 4-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
To check motor rotation 4-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
To check lowĆlimit 4-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Regulated Gas Pressure 4-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Computer Control Configuration 4-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Temperature Calibration 4-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

TABLE OF CONTENTS
ii
Belt Speed Calibration 4-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Closed Loop System 4-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Open Loop System - Single belt 4-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Open Loop System - Twin Belt 4-8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
motor control Board Adjustment 4-9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Rerating the Appliance 4-11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Checking the Firing Rate 4-12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5. TROUBLESHOOTING
DC Drive System 5-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Computer Control System 5-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Heating System 5-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Convection System 5-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. TECHNICAL APPENDIX
Intermittent Ignition System 6-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Principles of Operation 6-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Service Procedures 6-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Servicing the Invent Hood 6-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Illustrated Parts List 6-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cleaning and Maintenance 6-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Servicing Access 6-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Pressure Conversion 6-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Conversion Factors 6-9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cooking Computer - Temperature vs Resistance 6-10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Literature Addendum
??????
Rev - 10/9/96
Page 1 of 3
Operation - Cooking Computer without Conveyor Control
NOTE: This addendum applies to tandem ovens only.
CONTROL DESCRIPTION
1. DIGITAL DISPLAY - Displays the time, temĆ
perature and controller related information.
2. O EN ON/OFF - Controls power to the
oven.
3. NUMERIC KEYS - Used to enter numerical
data in the programming mode.
4. CLEAR KEY - Used to clear the display if an
error is made in the programming mode.
5. SET TEMP KEY - Used to view or program
the temperature setpoint.
6. ACT TEMP KEY - Used to view the current
oven temperature.
7. PROG/ENTER KEY - Used to enter and exit
the programming mode. Also used to lock
in programmed settings.
8. STATUS LAMPS - When lit indicate that the
fan or burners are operating.
NOTE:
This oven, supplied with remote
control, is equipped with an emerĆ
gency shut down switch.
Should you need to stop the heat
press the emergency switch.
WARNING:
Do not use the emergency switch as
a GENERAL on/off switch!
1
2
3
4567
8

Literature Addendum
2M7260.1 Rev - 9/5/96
Operation - Cooking Computer without Conveyor Control
OPERATION
To turn the oven on:
1. Turn the manual gas valve to ON.
2. Press and hold the ON/OFF key (2). The disĆ
play reads OFF when the oven is idle.
3. The display will flash WAIT  LOW  SET 
TI E  0.
4. The FAN and HEAT status lamps (9) light.
The fans begin to run. The heat rises to the
temperature setting stored in the computĆ
er's memory. The conveyor default time is 0.
To display the actual oven temperature:
1. Press the ACT TEMP key (6). The LED on
the key will light and the display reads ACĆ
TUAL  nnnnF.
To view the temperature set point:
1. Press the SET TEMP key (5). The LED on the
key will light and the display flashes SET 
TE P  nnnnF.
To turn the oven off:
1. Press the ON/OFF key (2). The fans will conĆ
tinue to run until the oven cools to a safe
temperature.
OVEN SHUTĆDOWN
Turn the Computer Controller off (press and moĆ
mentarily hold the ON/OFF key). Since the Cool
Down circuit is already energized, the blower
motor(s) will continue to run until the oven
reaches approximately180F (82C). The blowĆ
er motor(s) will then automatically shut off.
COOLĆDOWN CIRCUIT
Blodgett Mastertherm conveyor ovens are
equipped with a coolĆdown feature for motor
shaft and bearing protection. When the oven
reaches approximately 180F (82C), the relay
contacts close allowing the blower motor(s) to
continue to run regardless of the Computer
Controller status. As noted previously, the blowĆ
er(s) will continue to run until the temperature
drops below 180F (82C).
NOTE:
This oven, supplied with remote
control, is equipped with an emerĆ
gency shut down switch.
Should you need to stop the heat
press the emergency switch.
WARNING:
Do not use the emergency switch
as a GENERAL on/off switch!

Literature Addendum
??????
Rev - 10/9/96
Page 3 of 3
Operation - Cooking Computer without Conveyor Control
PROGRAMMING PROCEDURES
Programming the Cook Time:
1. The conveyor belt default time is 0.
Programming the Temperature:
1. Press the PROGRAM/ENTER key (8).
2. Press the SET TEMP key (5). The display
reads PROGĆ?  SET  TE PĆ?  _ _ _ _F.
3. Use the NUMERIC keys (3) to enter the deĆ
sired temperature set point. The control disĆ
plays the numbers as they are entered. If an
error is made, press the CLEAR key (4) and
reĆenter the number.
4. Press the PROGRAM/ENTER key (8) again.
5. Press the PROGRAM/ENTER key (8) a secĆ
ond time to lockĆin the new temperature.
The new temperature setpoint will be stored
in the computer's memory.
Operation at the Programmed Settings:
1. Press and hold the ON/OFF key (2).
2. The FAN and HEAT status lamps (9) light.
The fans begin to run. The heat rises to the
temperature setting stored in the computĆ
er's memory.
3. The display will flash WAIT  LOW  SET 
TI E  0 until the programmed bake temperĆ
ature is reached. The HEAT lamp (9) will reĆ
main lit until the oven reaches the temperaĆ
ture set point.
4. The display reads READY and the HEAT
lamp (9) goes out.
5. The oven is now ready to accept product.
6. Press and hold the ON/OFF key (2) to turn
the oven off. The fans continue to run while
the oven cools to a safe temperature.
DISPLAY INFORMATION
WAIT  LOW - indicates that the present oven
temperature is lower than the set point temĆ
perature. When the oven reaches the set
point temperature the display changes to
READY.
READY - indicates that the oven is ready to
accept product.
SET  TI E  0 - indicates the current cook
time setting.
HIGH  TI E - indicates that the temperature
is well above the set point. This usually occurs
when moving from a higher āto a lower temperĆ
ature. Wait until the display reads ready beĆ
fore loading product.
HIGH  TE P  LI IT - indicates that the oven
temperature exceeds the high limit. The Over
Temperature Alarm buzzer will sound. Shut
the oven off and wait for the unit to cool down.
HIGH  TE P  PANEL - indicates that the
control area reaches an excessive temperaĆ
ture. Shut the oven off and wait for the unit to
cool down.
PROBE  OPEN  PROBE  SHORT - indicates
that the temperature sensor has failed. The
Alarm buzzer sounds. Shut the oven off and
contact a service representative.
NOTE:
This oven, supplied with remote
control, is equipped with an emerĆ
gency shut down switch.
Should you need to stop the heat
press the emergency switch.
WARNING:
Do not use the emergency switch
as a GENERAL on/off switch!

INTRODUCTION
CHAPTER 1

T3870
1-1
OVEN SPECIFICATIONS
VENTILATION REQUIREMENTS
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.
Single Double Triple
CFM 1200Ć1650 2400Ć3300 3600Ć5000
M3/min 34 Ć 47 68Ć93 102Ć142
TABLE 1
ELECTRICAL SPECIFICATIONS
NOTE: Three Phase hookup is not permitted.
WARNING: DO NOT INSTALL A HIGH LEG" TO
ANY CONVEYOR OVEN!
Installations within the U.S.
The MT3870 requires a 15 Amp, 60HZ, 1F,
208Ć240 AC, 4 wire service consisting of L1, L2,
neutral and ground. See FIGURE 1. Use 90C wire
and size to National Electric or local codes.
Installations outside the U.S.
The MT3870 requires a 15 Amp, 50Hz, 1F, 230
AC, 3 wire service consisting of L1, neutral and
ground. See FIGURE 1. Use 90C wire and size
wire according to local codes.
CE approved installations
Connect the oven to a separate group 230 , 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.
NOTE: The burner control unit is phase sensitive.
If the phase and neutral are switched the
control locks out.
Connect exhaust fan connector 1 and 2. See
FIGURE 1. Connect phase + neutral + ground.
ÉÉ
ÉÉ
ÉÉ
s
Connector 1
2
L3
L2
L1
N
Fan
N
L
Blodgett
Connector
2Ć4Ć92
A2
A1
2
1
Relay A
2
1
Air Pressure Regulator
Burner Control Solenoid
CE Approved Installations
U.S. Installations Export Installations
L1
N
L2
120
120 208Ć240 OvenSupply
L1
N220Ć230 OvenSupply
FIGURE 1

INTRODUCTION
1-2
GAS SPECIFICATIONS
GAS CONNECTIONS
Domestic and General Export installations
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. 1.4 (Latest Edition). TABLE 2 should
be used as a guideline only.
NOTE: For any pipe runs over 50 feet (15 m), conĆ
sult the factory.
CE approved installations
1. Connect the oven to the gas line with the propĆ
er type of gas according to Local and National
Installation Standards. See TABLE 2.
GAS REQUIREMENTS
The firing rate for the MT3870 is 150,000 BTU/Hr.
(43.9 kW/Hr.)
NOTE: For natural gas meter sizing, consult your
local gas company to ensure that your meĆ
ter will provide the proper supply.
Installations within the U.S.
1. Add the total BTU's/hr of all the gas
appliances.
2. Convert BTU's to cubic ft/hr using the formula
Cu Ft/Hr = 1000 BTU/Hr for natural gas.
3. Size the meter accordingly.
Installations outside the U.S.
1. Add the total M3/min of all the appliances.
2. Size the meter accordingly.
DOMESTIC AND GENERAL EXPORT
Natural Gas Propane Gas
Gas Line Sizing
Single
Double
Triple
3/4" line
1Ć1/4" line
1Ć1/4" line
3/4" line
1 line
1Ć1/4" line
Orifice Size #1 #29
Incoming Gas Pressure W.C. kPa mbar W.C. kPa mbar
Static
Operational
7"
5.5"
1.74
1.36
17.4
13.7
12.5"
11"
3.11
2.73
31.1
27.4
CE APPROVED UNITS
Type of
Gas
Inlet
Pressure
mbars
Burner Pressure
mbars
Injector
Diameter
mm
Air
Opening
mm
Pilot
Injector
mm
Standard
Delivery
Value kW (HS)
G25 25 12 5,80 16 2 x 0,63 46 Nat. Gas
G20 20 8 5,80 16 2 x 0,63 46 Nat. Gas
G20/G25 20/25 Totally Inscrewed
Pressure Regulator
5,15 16 2 x 0,63 46 Nat. Gas
G30 30/50 17 3,48 16 2 x 0,30 46 Butane
G31 30/37/50 24 3,48 16 2 x 0,30 46 Propane
TABLE 2

T3870
1-3
ILLUSTRATED PARTS LISTS
ELECTRICAL COMPONENTS
NOTE:  = ASAP Distributor Required Stocking Parts
Ref.
No.
Part
No. Description
Ref.
No.
Part
No. Description
1M6474 Computer Control Kit, Closed
Loop SB (Qty 1)
1FW525 Computer Control Kit, Closed
Loop SB (Qty 1)
(Reconditioned)
M5635 Computer Control Kit, Open
Loop TB (Qty 1)
M3175 Decal, Lexan Control (Qty 1)
M7427 Probe, Temperature RTD, 500
OHMS (Qty 1)
M7202 Conversion Kit, Open Loop to
Closed Loop (Qty 1)
M3347 Cable, Computer Control, 25
Pin, 10' (Qty 1)
M3348 Cable, Computer Control, 9
Pin, 10' (Qty 1)
M3490 Cable, Computer Control, 25
Pin, 50' (Qty 1)
M3491 Cable, Computer Control, 9
Pin, 50' (Qty 1)
M3349 Harness, Inter-Connecting DC
Drive, 3-Wire (For 9 Pin)
(Qty 1)
M3353 Harness, Relay Board
(Open Loop) (For 25 Pin)
(Qty 1) (Before 9/15/95)
M7237 Harness, Relay Board (Closed
Loop) (For 25 Pin) (Qty 1)
(After 9/15/95)
2 M3314 Bracket, Computer Wall (Qty 1)
M5661 Bracket Assy., Cable Clamp
(Qty 1)
3M0984 Pick Up, P -2 (Qty 1) (After
9/15/95)
4 M7236 Board, Relay/Transformer
(Qty 1)
522672 Relay, Control (Qty 4)
6M3352 Transformer, 120 to 24
(Qty 1)
720349 Buzzer, 120 (Qty 1)
8M3295 Thermostat, High Limit
(Manual Reset) (Qty 1)
9M1362 Snap Disc, L140/20F, 2 Pole
SPST (Qty 1)
M2453 Snap Disc, L140/20F, 3 Pole
SPDT (Qty 1)
10 M0595 Switch, Air Pressure SPDT
(Qty 1)
11 M0152 Contact, Emergency Stop
Switch (Qty 1)
12 M3296 Activator, Emergency Stop
Switch (Mushroom Shape)
(Qty 1)
M3297 Nameplate, Emergency Stop
(Qty 1)
13 M0593 Terminal Block, 2 Pole (Qty 1or
CE Qty 2)
M2469 Fan, Axial 110 CFM 4 1/2" (Qty
4) (Before 11/14/95)
22718 Fan Guard & Hardware (Qty 3)
(Before 11/14/95)
M0572 Cord, Axial Fan 30" Power (Qty
4) (Before 11/14/95)
14 M6381 Blower, Cooling (Qty 1) (After
11/14/95)
15 M3136 Breaker, 7 AMP Circuit (Qty 4)
16 M2772 Breaker, 4 AMP Circuit (Qty 2)
M6590 Plate Assy., Control SB (Qty 1)
M7482 Plate Assy., Control TB (Qty 1)
M1694 Cord Set & Plug Assy., 10 Foot
(Qty 1)
M0772 Receptacle, Twist Lock (Qty 1)
17 M0708 Contactor, 3 Pole, 120 Coil
(Qty 1)
18 M3322 Hood Interlock, Mechanical
(Qty 1)