Blodgett MT2136 Series, Service And Repair Manual

Page: 37 / 94

MT2136
3-13
MT2136G DOMESTIC WITH REMOTE COMPUTER CONTROL - M3476 REV B
COMPONENT REFERENCE
NOTE: Refer to FIGURE 8 page 3-29 for compoĆ
nent locations.
1. COMPUTER (FW525)
2. BELT STOP RELAY (22672)
3. BLOWER RELAY (22672)
4. HEAT RELAY (22672)
5. DC SPEED CONTROL BOARD (M2379)
6. MANUAL RESETABLE HI LIMIT SWITCH
(M3295)
7. 115/24 VAC STEP DOWN TRANSFORMER
(M2381)
8. COMBUSTION MOTOR (22132)
9. CENTRIFUGAL SWITCH
10. IGNITION MODULE (M1054)
11. PILOT VALVE (LP - 22190, Natural - M5495)
12. BURNER VALVE (LP - 22190,
Natural - M5495)
13. MOTOR CONTACTOR (M0708)
14. CONVECTION FANS (Clockwise - M2871,
CounterĆclockwise - M2870)
15. SPDT THERMAL SWITCH (M2453 L140-20F)
16. COOLING FANS (M2469)
17. RTD PROBE (M7427)
18. SPST THERMAL SWITCH (M1362 L140-20F,
M2734 L165-30F)
19. BURNER CONTROL VALVE (20287)
20. FLAME BLOWER (22258)
21. 130 VDC MOTOR (M2378)
OPERATION
1. Apply power to the oven. Program the time and
temperature into the computer (1). The belt
stop relay (2), blower relay (3) and the heat
relay (4) energize powering up the oven.
2. When the belt stop relay closes, 120 VAC goes
to the DC speed control board (5) and the
manual resetable hi limit switch (6). The high
limit switch is a bulb and capillary style switch.
It reacts when the oven cavity temperature exĆ
ceeds the high limit programmed into the
cooking computer.
If the high limit switch is closed power flows to
the primary side of a 115/24 volt step down
transformer (7) and the combustion motor (8)
of the flame blower. The combustion motor
powers up. When the combustion motor
reaches full speed, a centrifugal switch (9)
closes sending 24 VAC to the ignition module
(10). After the module's self diagnostics are
complete, the pilot valve (11) opens. When a
proof of flame is established the main burner
valve (12) powers up.
3. The blower relay (3) sends 115 volts to the coil
of the motor contactor (13) starting the two
convection fans (14) in the rear of the oven.
This contactor also supplies power to the N.C.
terminal of a SPDT thermal switch (15). 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. terminals sending
power to the cooling fans (16).
NOTE: The SPDT thermal switch is located in
the junction box in the rear of the oven
in the blower compartment.
4. On a call for heat from the cooking computer
(1), as sensed by an RTD probe (17), the heat
relay (4) closes sending 115 VAC to one termiĆ
nal of a N.C. SPST thermal switch (18). The
switch toggles if the temperature passing its
face exceeds the rating on the back of the
switch. If the switch is closed, 115 VAC is delivĆ
ered to the burner control valve (19). This valve
opens sending gas to the flame blower (20) for
ignition.
NOTE: The RTD probe is located in front of the
combustion motor. It should be checked