Impinger 3270 Service Manual – Dom & Int’l
4
SEQUENCE OF OPERATION - DOMESTIC
Model
Gas Type
Voltage
Hz.
Phase
3270
Natural Gas
120 VAC
60 Hz
1 Phase
3270
LP Gas
120 VAC
60 Hz
1 Phase
POWER SUPPLY
Electrical power to be supplied to the oven by a three conductor cordset.
Voltage from the black conductor to the white conductor to be 120VAC.
- White conductor is Neutral
- Green conductor is Ground
CONTROL BOX
AUTO COOL DOWN
When the temperature in either one of the control boxes reaches 120°F ± 3°F
(49°C ± 1.7°C), the cooling fan thermostats will switch power to the cooling fans.
The thermostats will interrupt power to the cooling fans when the temperature
falls to 100°F ± 3°F (37°C ± 1.7°C).
MAIN FAN CIRCUIT
120VAC is permanently supplied through a 15 amp fuse to the normally open
double pole power switch, to a normally open set of contacts on the main fan
relay and the normally open cooling fan thermostats. Closing the power switch
supplies 120VAC to the coil of the time delay relay. These normally open
contacts now close supplying 120VAC to the time delay which then supplies
120VAC to the main fan relay coil closing the normally open contacts, which then
supplies 120VAC to the main fan motors.
BURNER CIRCUIT
Closing the Oven Power Switch also supplies 120VAC to the burner blower
motors. NOTE: This oven utilizes two (2) complete Burner/Temperature Control
systems. The sequence of operations is the same for each system. 120VAC is
supplied, through the Centrifugal Switch of the Main Fan Motor (this switch
closes when the Main Fan reaches approximately 900 R.P.M.) to the primary of
Ignition Control Transformers. As the Burner Blower reaches approximately
1600 R.P.M., its internal centrifugal switch will close, supplying 24VAC to the
ignition control. The Ignition Control operates on both 24VAC and 120VAC.
When the control is energized by 24VAC, 120VAC is switched to the Hot Surface
Igniter for 45 seconds for Hot Surface Igniter warm up. The igniter glows red,
24VAC is switched to the MV/PV gas valve which opens, and ignition should now
occur. If ignition does not occur in 6 seconds, the control will lock out. To
recycle after lockout, turn off the main oven switch for 45 seconds and then turn
the switch back on.
TEMPERATURE CONTROL
When the Oven Power Switch closes, power is supplied to the Oven Control
Transformers which supply 24VAC to the oven controls (TWO CONTROLS –
one for the left side of oven, one for the right side of oven). The oven control is
set to a desired temperature. Thermocouples will provide varying millivolts to the
oven controllers. The oven controllers supply 3-24VDC to the modulating valve
to maintain desired temperature.
CONVEYOR DRIVE
Line voltage (120VAC) is supplied to the conveyor motor. The conveyor speed is
controlled by an increase or decrease in frequency for the conveyor controller.
Secondary voltage, 24VAC, is supplied to the oven control. Setting the oven
control to the desired time, outputs line voltage, through a reversing switch, to
the conveyor motor.
Speed is monitored via frequency output from the hall effect sensor.
NOTE: The conveyor control uses a hall effect sensor and magnet mounted in the conveyor motor that senses the
motor speed. Any change in motor load (± R.P.M.) is detected by the sensor and the frequency to the motor is
adjusted accordingly.
