Automatic kettle

[FredPuli43]

Just wondering how it is that my automatic kettle 'knows' when to switch off. Has it got a sensor that reacts to the temperature of the water itself, or is it reacting to the water vapour temperature in the spout or, if not, how is it doing it?

[You can see I'm not busy at the moment, but think what happened when James Watt watched a kettle!]

[ChuckFickens]

Normally there is a vent for steam to enter at the top of the kettle on the handle side, when the water boils the steam enters the vent and triggers a thermostat to switch the kettle off.

[Celticv11]

Probably a bi- metal switch in the thermostat, two different metals that expand at different speeds that causes the plate to buckle and touch the microswitch at boiling point

[rojash]

Apparently, the first automatic kettle had a bi-metal strip in the lid, but, as Chicken Licken says, most nowadays have a thermostat in or about the top of the handle.

[Celticv11]

How do they work? The simplest ones are mechanical and use a bimetallic thermostat (described in our main article on thermostats) integrated into the element unit at the bottom of the kettle. It consists of a disc of two different metals bonded tightly together, one of which expands faster than the other as the temperature rises. Normally the thermostat is curved in one direction, but when the hot water reaches boiling point, the steam produced hits the bimetallic thermostat and makes it suddenly snap and flex in the opposite direction, a bit like an umbrella turning inside out in the wind. When the thermostat snaps open, it pushes a lever that trips the circuit, cuts off the electric current, and safely switches off the kettle.

[ChuckFickens]

I can't wait for your article on thermostats :)

[paul1763]

think its something to do with steam pressure, our kettle will not switch off if the lid is not closed proprely

[Celticv11]

Ha ha ,yes i know, but i thought it was too simplistic just to say " it,s got a thermostat" so i thought i would explain how a thermostat works, if your kettle clicks off, it probably has one of these type,very reliable and simple. :)

[ChuckFickens]

That's only because the steam won't enter the area where the thermostat is when the lids open as it rises straight out the top of the kettle.

I guess technically it is the increased pressure caused by the lid being shut that makes the steam get to the thermostat, but it's not the pressure that actually triggers the kettle turning off.

[mccfluff]

its the pixies...

[ChuckFickens]

I prefer my pixies grilled, rather than boiled.

[sunny-dave]

There's a little blue light in mine, to make it easier for the kettle elf to see when the water is boiling :)

[FredPuli43]

Oh, yes Dave. Mine has a glowing blue light that dances about. That must be the signal.

[mccfluff]

elves are too big to fit in kettles, they look after the boilers

do you lot know anything???

[Toureman]

Yeah, that's true when my boiler died the engineer told me my elf had escaped so he chained the new elf to one of the pipes!

[FredPuli43]

Don't know about elf heating , but my mother had a "Goblin heater" once. Come to think of it, a goblin made the tea; "goblin teas made" she used to say.

[bellazella]

You need to get out more lol