Repair manual

MT1828
2 --- 9
MT1828G CE OVENS --- M6462 REV B
COMPONENT REFERENCE
NOTE: Refer to FIGURE 5 for component loca-
tions.
1. COMPUTER
2. MAIN CONTROL RELAY
3. BLOWER RELAY
4. BURNER VALV E RELAY
5. MOTOR CONTACTOR
6. SINGLE POLE DOUBLE THROW THERMAL
SWITCH
7. CONTROL COMPARTMENT COOLING F AN
8. SPEED CONTROL BOARD
9. RESETABLE HI LIMIT
10. CONVECTION BLOWER PRESSURE SWITCH
11. CONVECTION BLOWERS
12. FLAME BLOWER
13. BURNER PRESSURE SWITCH
14. LATCHING RELA Y
15. PURGE TIMER
16. SINGLE POLE SINGLE THROW RELA Y
17. SINGLE POLE SINGLE THERMAL SWITCH
18. IGNITION CONTROL MODULE
19. H.S.I.
20. DUAL SOLENOID GAS VALVE
21. PROOF OF FLAME ROD
22. SINGLE POLE DOUBLE THROW SWITCH
23. COOLING FANS
24. D.C. DRIVE MOTOR
OPERATION
1. Apply power to the oven. Program time and
temperature into the computer (1). The main
control relay (2) blower relay (3) and burner
valve relay (4) will energize.
2. The blower relay (3) s ends power to the coil of
the motor contactor (5) and the N.C. terminal
of a single pole double throw thermal switch
(6). This switch starts the control compartment
cooling fan (7). The motor contactor energizes
the convection blowers (11) and the N.C. ter-
minal of another thermal switch (22).
3. The main control relay (2) sends 230 VAC to
the speed control board (8) a nd the resetable
hi limit (9).
4. If the hi limit (9) is closed, power goes to the
convection blower pressure switch (10). This
switch closes when the convection blowers
(11) are operating. I f t he switch is closed, pow-
er goes to the flame blower (12), the common
terminal of the burner pressure switch (13) and
terminal #7 of the latching relay (14).
5. If the burner pressure switch (13) is closed be-
tween COM and N.C., power goes to #4 and
the coil of the latching relay (14). This closes
the relay from #4 to #7 and #6 to #9. The relay
remains latched due to the power on #7 run-
ning through #4 t o the coil.
6. When the flame blower (12) reaches speed, a
differential in pressure is created in the burner
pressure switch (13). The switch toggles from
COM and N.C. to COM and N.O. This supplies
power to #9 of the latching relay (14) which
should be closed through to #6, sending pow-
er to a purge timer (15).
7. When the purge timer (15) times out it sends
powertothecoilofasinglepolesinglethrow
relay (16).
8. If the burner valve relay (4) is closed, power
goes to a single pole single throw thermal
switch (17). This switch a cts as a control hi lim-
it. It opens if the ambient air temperature
reaches the range on the back of the switch.
9. If the switch is closed, power goes through the
closed set of contacts in the relay (16) to termi-
nal #17 of the ignition module (18).
10. Aft er a warmup period for the H.S.I. (19), the
ignition control module (18) powers up the
dual solenoid gas valve (20). If the proof of
flame rod (21) does not sense a flame in 1 sec-
ond, the ignition control module shuts the sys-
tem down.
11. Thesinglepoledoublethrowswitch(22)gets
its power from the motor contactor (5). This
switch is closed between the common and
N.C. terminals, powering the cooling fans (23).
The switch toggles if the ambient air passing
the facing of the switch exceeds the number on
the back of the switch.
12. The D.C. drive motor (24) get s voltage from the
speed control board (8). The speed of the drive
motor varies with the time programmed into
the computer. The voltage range for this board
is from 20 to 180 V.D.C. measured at A1 and A2
of the speed control board (8).