Repair manual

MT1828
2 --- 7
MT1828E DOMESTIC AND GENERAL EXPORT OVENS --- M6314 REV C
COMPONENT REFERENCE
NOTE: Refer to FIGURE 4 for component loca-
tions.
1. COMPUTER
2. BLOWER RELAY
3. BELT STOP RELAY
4. HEAT RELAY
5. 208/120 STE P DOWN TRANSFORMER
6. MOTOR CONTACTOR
7. SINGLE POLE DOUBLE THROW THERMAL
SWITCH
8. CONVECTION FANS
9. COOLING F ANS
10. SPEED CONTROL BOARD
11. D.C. MOTOR
12. SINGLE POLE SINGLE THROW THERMAL
SWITCH
13. RESETABLE HI LIMIT
14. CONTACTOR
15. ELEMENTS
OPERATION
1. Apply power to the oven. Program the time and
temperature into the computer (1). The blower
relay (2), belt stop relay (3) and heat relay (4)
are energized.
2. If the contacts in the blower relay close the 110
V.A.C. supplied from the 240/120 step down
transformer (5) will go to the coil of the motor
contactor (6) and the N.C. terminals of two
single pole double throw thermal switches (7).
These switches toggle when ambient air pass-
ing the face of the switch exceeds the rating on
the back of the switch.
3. If the motor contactor (6) and the thermal
switches (7) are closed the convection fans (8)
and cooling fans (9) will start.
4. Thebeltstoprelay(3)shouldbeclosedsend-
ing 110 V.A.C. to t h e speed control board (10).
5. If the speed control board is working it sends
out a variable amount of D.C. voltage to the
D.C. motor (11). The voltage can vary from 20
to 130 VDC depending on the amount of time
programmed into the computer (1).
6. The heat relay (4) closes with a call for heat
sending power to a single pole single throw
thermal switch (12). This switch a cts as a tem-
perature limiting device for the controls and
opens if the ambient air around the control ex-
ceeds the rating on the back of the switch.
7. If the switch is closed, 110 VAC goes to t he re-
setablehilimit(13).Thisswitchactsasanoven
hi limit a nd opens if t he temperature in the oven
exceeds 630_F (333_C).
8. If the resetable high limit switch is closed the
power will go to one side of the contactor coil
(14). This contactor powers the elements (15).
9. When the motor contactor (6) closes the con-
vection fans (8) start. If the thermal switches
are closed between the N.C. a nd C. terminals
the cooling fans (9) will start.