Blodgett MT2136 Series, Service And Repair Manual

Page: 39 / 94

MT2136
3-15
MT2136G DOMESTIC WITH OPEN LOOP COMPUTER CONTROL - M3717 REV B
COMPONENT REFERENCE
NOTE: Refer to FIGURE 9 page 3-30 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. SPST THERMAL SWITCH (M0635 F10-20)
18. RTD PROBE (M7427)
19. SPST THERMAL SWITCH (M1362 L140-20F,
M2734 L165-30F)
20. BURNER CONTROL VALVE (20287)
21. FLAME BLOWER (22258)
22. 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.
NOTE: The SPDT thermal switch is located in
a junction box in the convection fan
compartment.
If this switch is cold, it should be made beĆ
tween common and N.C. terminals sending
power to the two cooling fans (16) located in
the rear of the oven. These cooling fans protect
the convection fans from high ambient heat.
Two additional cooling fans (16) are located in
the cooking computer control area and are acĆ
tivated when a SPST N.O. thermal switch (17)
closes. 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.
NOTE: The SPST N.O. thermal switch is located
in the cooking computer compartment.