Ignitor Circuit Operation - GE GTUP270EMWW Technical Service Manual

Ignitor Circuit Operation

The glo-bar ignitor circuit is made up of the following components: a gas valve with safety and main valves,
ignitor, and a fl ame detector. The safety valve is actuated by a double coil that comprises a safety coil
(resistance approximately 1400 ohms) and a booster coil (resistance approximately 580 ohms). Both coils
are needed to open the safety valve. Once energized, the safety coil alone will hold the valve open. The main
valve has a single coil (resistance approximately 1300 ohms).
L1
N
L1
N
IGNITOR
IGNITOR
(GLOWING RED) DETECTOR
(NOT GLOWING) DETECTOR
MAIN
BOOSTER
BOOSTER MAIN
SAFETY
SAFETY
Gas Valve Open
Ignitor On
The fl ame detector (less than 1 ohm) is mounted on the combustion chamber. It is normally in the closed
position (N.C.). The fl ame detector is opened by the radiant heat produced by the glo-bar and once open, the
fl ame detector will be held open by the radiant heat produced by the gas fl ame.
When the control system calls for heat, the following circuits are energized:
1. L1 power is sent from the timer, through the outlet control and safety thermostats, to the gas valve.
2. Neutral circuit is from the dryer harness through the door switch and motor switch M2 to M1 to the gas
valve.
When the glo-bar is heating, the booster and safety coils are both energized and will open the safety valve.
The main valve is closed as its coil is bypassed by the N.C. fl ame detector. When the glo-bar reaches ignition
temperature, in approximately 60 seconds or less, the fl ame detector is heated and opens, placing the main
coil in series with the glo-bar. The main valve opens, allowing gas to fl ow into the combustion chamber and
ignite. The main coil, now in series with the glo-bar, causes the glo-bar to cool down. However, the fl ame
detector is held open by the radiant heat from the gas fl ame. The booster coil is now also in series with the
main coil and is essentially inoperative. Should a momentary power failure occur, the gas valve will shut
off and an attempt to restart will not occur until the fl ame detector cools and resets, in approximately 30
seconds.
– 38 –