Blodgett MT2136 Series, Service And Repair Manual

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MT2136
3-9
MT2136G AUSTRALIAN UNIT WITH ATHENA CONTROL - M2847 REV C
COMPONENT REFERENCE
NOTE: Refer to FIGURE 6 page 3-27 for compoĆ
nent locations.
1. BLOWER SWITCH (M0153)
2. HI/LO LIMIT BOARD (M3150)
3. TEMPERATURE CONTROLLER (M3149)
4. MOTOR CONTACTOR (M2247)
5. CONVECTION FANS (Clockwise - M2873,
CounterĆclockwise - M2872)
6. THERMOCOUPLES (Dual lead - M3151,
Single - M3152)
7. HEAT SWITCH (M0152)
8. CONVECTION FAN PRESSURE SWITCH
(M0595)
9. STEP DOWN TRANSFORMER (M2384)
10. COMBUSTION MOTOR (M2386)
11. IGNITION MODULE (M1054)
12. PILOT VALVE (LP - 22190, Natural - M5495)
13. MAIN BURNER VALVE (LP - 22190,
Natural - M5495)
14. SPST THERMAL SWITCH (M1362, L140Ć20F
or M2734, L165Ć30F)
15. SPST THERMAL SWITCH (M1362, L140Ć20F
or M2734, L165Ć30F)
16. DIFFERENTIAL PRESSURE SWITCH (M2819)
17. SINGLE SOLENOID GAS VALVE (M2245)
18. COOLING FANS (23034)
19. SPST THERMAL SWITCH (M0635, F110Ć20F)
20. SPST THERMAL SWITCH (M0635, F110Ć20F)
21. CONVEYOR SWITCH (M0152)
22. TIME DISPLAY (M3154)
23. 10k
W POTENTIOMETER (M3145)
24. DC SPEED CONTROL BOARD (M3153)
25. 180 VDC MOTOR (M3128)
26. #10 HALL EFFECT PICKUP (M3147)
OPERATION
1. Turn the blower switch (1) to ON. The N.O. conĆ
tacts close, the N.C. contacts open. 115 VAC
runs to terminal #7 of the hi/lo board (2), L1 of
the temperature controller (3) and the coil of
the motor contactor (4). Terminal #7 is an outĆ
put. It remains powered after the oven is shut
down to keep the convection fans (5) operatĆ
ing until the unit reaches 135Ć170 F (57Ć77 C)
as sensed by the thermocouples (6).
NOTE: Two thermocouples are located beĆ
tween the convection fans in the rear of
the oven. One thermocouple provides
DC millivolts to the Hi/Lo limit board.
The other provides DC milivolts to the
temperature controller. Check thermoĆ
couples with a millivolt meter.
2. Turn the heat switch (7) to ON. 240 VAC is supĆ
plied to terminal #5 of the hi/lo board (2). If the
temperature is below 316 C (600 F) a switch
is made between terminals #5 and #6 allowĆ
ing power to go to one side of a N.O. convecĆ
tion fan pressure switch (8).
NOTE: This switch reacts to a vacuum created
by the convection fans (5).
When the switch closes, 240 VAC is delivered
to the primary side of a 240/24 VAC step down
transformer (9) and the combustion motor (10)
of the flame blower. When the transformer
powers up, 24 VAC are sent to the ignition
module (11). After the module's self diagnosĆ
tics are complete, the pilot valve (12) opens.
When a proof of flame is established, the main
burner valve (13) opens.
3. Terminal #5 of the hi/lo board (2) sends power
to the common terminal of the temperature
controller (3). If the temperature controller (3)
is calling for heat, a switch is made between
common and N.O. Power is sent to one side of
a N.C. SPST thermal switch (14). The switch
toggles if the temperature passing its face exĆ
ceeds the rating on the back of the switch.
NOTE: The switch is located in the slide out
control compartment. It protects the othĆ
er components from hi ambient heat.
If this switch is cold it should be closed, sendĆ
ing power to one side of another N.C. SPST
thermal switch (15). The switch toggles if the