Blodgett MT3870, Руководство по обслуживанию и ремонту

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MT3870
3-5
CE OVENS
COMPONENT REFERENCE
NOTE: Refer to FIGURE 3 for component locaĆ
tions.
1. BLOWER RELAY
2. MOTOR CONTACTOR
3. CONVECTION FANS
4. CONVECTION PRESSURE SWITCH
5. BELT STOP RELAY
6. DC SPEED CONTROL BOARD
7. MANUAL RESET HI LIMIT SWITCH
8. HEAT RELAY
9. SINGLE POLE SINGLE THROW THERMAL
SWITCH
10. SINGLE POLE SINGLE THROW RELAY
11. TRIPLE POLE DOUBLE THROW RELAY
12. DIFFERENTIAL BURNER PRESSURE
SWITCH
13. COMBUSTION BLOWER MOTOR
14. TEN SECOND PURGE TIMER
15. LANDIS & GYR IGNITION CONTROL SYSTEM
16. 2 SECOND TIMER
17. DUAL SOLENOID GAS VALVE
OPERATION
1. Apply power to the oven. Program the time and
temperature into the computer. The blower
relay (1), belt stop relay (5) and heat relay (8)
pull in and power up three separate circuits.
The voltage to the relay coils is 12 VDC.
2. The blower relay (1) closes sending 230 volts
to the coil of the motor contactor (2). Points 1,
2, 5 and 6 close powering the convection fans.
3. The convection fan pressure switch (4) closes
due to the vacuum that is established in the
burner tube chamber by the operation of the
convection fans.
4. The belt stop relay (5) sends 230 volts to the
DC drive board (6) and the manual reset hi limit
switch (7).
NOTE: This relay will only be powered if there
is a time programmed into the computĆ
er. THE OVEN WILL NOT HEAT IF TIME
IS NOT PROGRAMMED INTO THE
COMPUTER.
5. The heat relay (8) sends 230 volts to a single
pole single throw thermal switch (9). If closed
the relay continues to send power to one side
of a single pole single throw relay (10). This
relay will not see power at it's coil until a triple
pole double throw relay (11) closes.
6. Once the convection fan pressure switch (4)
closes, 230 volts go to a differential pressure
switch (12), the combustion blower motor (13),
terminal #7 and the coil of the triple pole
double throw relay (11).
7. When a differential is sensed at the differential
pressure switch (12) the switch changes posiĆ
tion allowing power to go to terminal #9 of the
triple pole triple throw relay (11). This relay is
a latching relay and is held closed by power
that was applied at terminal #7.
8. Power flows from terminal #8 of the triple pole
double throw relay (11) to a ten second purge
timer (14). This timer allows the combustion
blower (13) to operate for ten seconds allowing
the combustion chamber to clear of any comĆ
bustible gasses.
9. After the timer times out the voltage is applied
to the other side of the coil of the single pole
single throw relay (10). When that set of conĆ
tacts closes, voltage goes to terminal #1 of the
Landis & Gyr ignition control system (15). TerĆ
minal #8 will send power to one side of a two
second timer (16) and the pilot coil of the dual
solenoid gas valve (17). After two seconds
elapse, the voltage is applied to the main coil
of the dual solenoid gas valve (17). If proof of
flame is strong the ignition system stays powĆ
ered up. Should the flame signal be lost, the
ignition control system will lock out.
10. Two sets of contacts are used as a hood interĆ
lock in the motor contactor (2), terminals #13
and #14. At this point there is no power to
these terminals, they act only as a switch to
turn on the hood when the oven is turned on.
NOTE: This is an option that the customer may
use, it is not a requirement.