I don’t think my title is very good but I didn’t want it to be too long
The way that my gas hob works is that I push in and turn
the knob of the burner that I want to use so that the gas starts coming out. When I activate the spark and the burner is lit I can stop pushing in the knob and the gas will keep flowing. If I stop pushing in the knob without lighting the burner then the gas stops flowing immediately, even though I haven’t turned the knob back to zero. Why does the gas not keep flowing like it does when the burner is lit?
In: Other
I know this – there is something called a [flame failure device](https://en.m.wikipedia.org/wiki/Flame_supervision_device)
I know this because our cooker broke, and I diagnosed and replaced a faulty flame failure device. Which, looking back on it, was pretty dumb, as I couldn’t have been more than about 14 at the time. God knows why my parents let me attempt it. Though I guess it worked
The burner contains a device called a thermocouple – it acts as a switch that reacts to the presence of sufficient heat. If the heat (from the lit burner) is not there, the thermocouple will switch the gas off.
If you look closely at your burner you might see what looks like a tiny wire poking into the flame in one spot. This is a thermocouple. It is connected to a gas valve and will keep this open when the thermocouple is hot. But once the thermocouple becomes cold it shuts the valve and the gas can no longer flow to the burner. When you push the knob for that burner inn you are bypassing the thermocoupled valve so gas can flow to the burner even when not lit.
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