Lang GCCO-T Service Manual page 35

Power switch turned to "ON" position.
Power to oven light switch.
120 volts to rows "A" and "B" of 24 pin terminal block.
120/24-volt transformer energized.
24 volts to rows "C" and "D" of 24 pin terminal block.
24 volts to common of back-up toggle switch.
24 volts to pin "A" on back-up relay.
24 volts to 6 (Johnson Control), TH (Channel Products), and ground of spark module.
Spark module begins sparking at pilot burner.
24 volts to pilot valve coil of combination gas valve.
Pilot valve opens.
Gas flows to pilot burner.
Pilot burner lights.
Pilot light confirmed by spark module.
12 to 13 micro amps on pin 4 (Johnson Control), and Sens (Channel products).
24 volts from pin 3 (Johnson Control) and MV (Channel products) to common of back-
up toggle switch.
Back-up toggle switch "OFF".
Circuit 1
24 volts across "D" and TP4, TP5, and TP6.
24 volts to motor relay through door switch.
Motor centrifugal switch closes.
Circuit 2
24 volts to terminal "B" on back-up relay.
Back-up relay closes, energizing 120/12 volt transformer.
12 volts to TP1.
Computer starts.
Product selected from Control panel.
24 volts from TP5 through safety thermostat, through centrifugal switch in motor, to
main valve .coil of gas combination valve.
Main valve opens.
Gas flows to main burners.
Main burners light.
Back-up toggle switch "ON".
Circuit 1
24 volts to motor relay.
Motor relay closes.
Motor centrifugal switch closes.
Circuit 2
24 volts to Back-up thermostat.
Temperature set on Back-up thermostat.
24 volts from Back-up thermostat through safety thermostat, through centrifugal switch
in motor to main valve coil of Gas combination valve.
Main valve opens.
Gas flows to main burners.
Main burners light.
SEQUENCE OF OPERATION GCCO-C
35