Gas Valve & Ignitor Circuit Operation (Gas Models) - Fisher & Paykel DE09 Service Manual

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5.3.5 Gas Valve & Ignitor Circuit Operation (Gas Models)
The gas valve system has 2 coils, a booster coil and a main coil, which are operated by
thermostats, and a safety coil. There are three thermostats that operate the temperature control of
the gas valve. There is also a flame detector that operates the coils and the ignitor.
Power is supplied from terminal A on the timer to terminal 15 on the selector. The circuit is
switched to terminal 16 and then looped to terminal 7. From the selector, power feeds through the
drum outlet thermostat and then the safety thermostat to the gas valve assembly.
The gas valve assembly operates in two modes, ignition and run. The safety coil is energised
during both modes.
When in ignition, the flame detect thermostat is closed. Power feeds through the booster coil and
the ignitor because these are in parallel circuit, causing ignition. When the flame has heated the
flame detect thermostat, it opens and the valve goes into run mode.
Ignition Circuit
When the flame detect thermostat opens, the booster coil and the main coil are in series circuit, so
power is dropped in the booster and is activated in the main. The ignitor is also dropped in
voltage, so stops igniting.
The neutral circuit runs through the inlet thermostat, through the motor switch and back to the main
neutral connection.
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