Blodgett MT3255 Series, Руководство по обслуживанию и ремонту

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MT3255 and MT3270
3---13
MT3270 TWIN BELT WITH REMOTE CONTROLS --- M4410 REV A
COMPONENT REFERENCE
NOTE: Refer to FIGURE 9 page 3---24 for compo-
nent locations.
1. COMPUTER (FW525)
2. BLOWER RELAY (22672)
3. MAIN CONTROL RELAY (22672)
4. BURNER VALVE RELAY (22672)
5. SPEED CONTROL BOARDS A & B (M2379)
6. SPST THERMAL SWITCH (M1362)
7. MANUAL RESETABLE HI LIMIT (M3295)
8. PRESSURE SWITCH (M0595)
9. 115/24 VAC TRANSFORMER (M2381)
10. PURGE RELAY (M2382)
11. COMBUSTION MOTOR (22132)
12. CENTRIFUGAL SWITCH
13. IGNITION CONTROL SYSTEM (M1054)
14. PILOT VALVE (LP --- 22190, Natural --- M5495)
15. MAIN VALVE (LP --- 22190, Natural --- M5495)
16. MOTOR CONTACTOR (M0708)
17. CONVECTION FANS (Clockwise --- M4224,
Counter-clockwise --- M4225)
18. COOLING FANS (4-1/2” --- M2469,
3-1/5” --- 21134)
19. SPDT THERMAL SWITCH (M2453)
20. D.C. MOTOR (M2378)
21. RTD PROBE (M7427)
22. EMERGENCY SHUTDOWN SWITCH (M0152)
OPERATION
1. Apply power to the oven. Program the time and
temperature into the computer (1). The burner
valve relay (4), blower relay (2) and main con-
trol relay (3) energize powering up the oven.
2. The main control relay (3) sends power to the
front and rear speed control boards (5) and the
SPST thermal switch (6). The switch toggles if
the temperature passing its face exceeds the
rating on the back of the switch. If the thermal
switch is closed, power is supplied to the
manual reset high limit switch (7). The high lim-
it switch is a bulb and capillary style switch. It
reacts when the oven cavity temperature ex-
ceeds the high limit programmed into the
cooking computer.
If the high limit switch is closed power flows to
the convection fan pressure switch (8). The
switch reacts from a vacuum created by the
convection fans.
If the pressure switch is closed, power runs to
the primary side of a 115/24 VAC transformer
(9) and a contact on the purge relay (10).
These components are located in a box
mounted on top of the combustion motor.
When 24 VAC are applied to the purge relay,
the contacts close sending 115 VAC to start
the combustion motor (11). When the combus-
tion motor reaches full speed, a centrifugal
switch (12) closes sending 24 VAC to the igni-
tion module (13). After the module’s self diag-
nostics are complete, the pilot valve (14)
opens. When a proof of flame is established,
the ignition control module (13) sends 24 VAC
to terminal #6 of the burner valve relay (4). If
this relay is closed on a call for heat, as sensed
by an RTD probe, a circuit is completed be-
tween terminal #6 and #5 sending 24 VAC to
the main valve (15).
NOTE: The RTD probe is located between the
two middle convection fans in the rear
of the oven. Check the probe with an
ohm meter.
3. The blower relay (2) sends 115 volts to the coil
of the motor contactor (16) starting the four
convection fans (18) in the rear of the oven.
This contactor also supplies power to the N.C.
terminal of a SPDT thermal switch (19). The
switch toggles if the temperature passing its