How does an Electric Tea Kettle know when to turn off?

The age old question: How does your electric tea kettle know when to turn off? Is it electronic, or something simpler?
It turns out the key is a bimetallic strip. At a certain, carefully adjusted temperature, the bimetallic strip will bend just enough such that right when the water starts to boil, the bent strip will trigger the mechanism that flips the switch to the OFF position.
It doesn't matter how much water is in the pot. Once the water is boiling, the temperature in the base will be at a certain point. That temperature point is the trigger threshold for the bimetallic strip. More or less.
That sounds complicated, but watch the video. It's pretty simple!
More techie tips: scottiestech.info

[@samjc100]

Thanks for this video! Another important point to mention is how the bimetalic strip gets heated: -As some other comments have mentioned, the boiling point of water changes at different altitudes and you need the temperature switch to be impossibly accurate if it is to switch off when the water reaches boiling, but not before that -The way this is resolved is that the bimetalic strip is actually heated by steam, directed through a pipe from the top of the kettle -This steam only makes it down the pipe to heat the strip once the kettle is boiling, such that there is a pressure build up from the steam to push it down the pipe -That is why your kettle won't stop boiling if you leave the lid off! Hope that's helpful :)

[@KooriGraywolf]

Yes! This was also part of my question. I noticed that if my kettle was not properly closed it could go on boiling forever.

[@ms-9]

Right on. Thanks

[@naderiskandar1896]

Perfect ! thanks

[@learnmore5490]

Now clear, thanks!

[@allenvanhellen2572]

How do you fix it when it no longer turns the kettle off automatically?

[@Y.M...]

Love the internet. 7 minutes ago, I just asked myself this question as I waited for my tea, and now I just watched the answer unfold over a cup of tea. Thank you!

[@terryjefferson747]

you prolly dont give a shit but does any of you know of a trick to get back into an instagram account? I was stupid lost the password. I would love any tricks you can offer me!

[@누구세옹]

What a nice video to understand the principle of bimetal switch. Thanks a lot from South Korea 🇰🇷

[@gedomazo2309]

That was very helpful, i managed to repair my electric pot auto switch off by bending that to metal strip you pointed out after watching this video. Its been 3 months since the last time it work now its working fine again. Thank you very much.

[@ScottiesTech]

Glad I could help!

[@Jessicajil]

Thank you ... that's so clear. The switch on my kettle won't stay on so I was trying to work out what turned it off. Now I need to work out why it turns off too soon!

[@rinnin]

Same problem here. Wondering if you had any luck. Did you need to replace that bimetallic switch?

[@mads4it555]

I've been wondering for a while. Thank you for the excellent explanation and simple demonstration. Now I've seen how it works in detail. My curiosity itch has been scratched! 👍

[@crumbelievability]

Great video! Helped me figure out how fix my kettle not shutting off by cleaning rust off the strip.

[@nang2000]

I’m so happy I’m not the only one thinking how kettles switched off and I’m more happy someone made a video about it lol

[@EpicEternal2]

great video about how the current shuts down by bimetalic plate! However, My kettle turns on and starts warming but switches off before water boils. If I switch it back on it works for a few seconds before it trips again. What does keep the switch down in place when we manually push it? because I know it can not stay down when it is not powered, so there has to be an active mechanism for that as well. I appreciate it if you help me or even more if you make a video and tutorial. Thanks!

[@joshuahankey]

Wow this is so cool! i was thinking about modding a tea kettle to make a boiler for an espresso machine and this save me so much time. thanks!!

[@GGN-92]

Thanks for these very clear explanations.

[@Christs_Apologet]

Great video, helped a lot. Appreciate it

[@mohammedhakumi5959]

Thanks a lot Scotties for this video , but can u please help me to fix a thermal switch which refuse to be latched on when I switch it "On" ..... the kettle boiling water , only I have to keep pressing the switch On by my finger, so how can I fix it please ? (The switch is the same shape of the one in this video of yours)

[@mayod111]

And now I can run my kettle till it explodes 😂

[@Techben16]

Thank you for your very informative video! I was wondering how they turn off lol.

[@guima20]

Very good. Thank you. Another thing I have learned in my life. Much appreciated!

[@MrPranoybiswas]

I liked your explanation and some crazy music in between😂

[@spettro9]

Thank you for the video Bob Ross meets Benedict Cumberbatch meets Mr Wizard!

[@markkelly9225]

On mine, there are two additional bimetallic switches underneath the black plastic assembly that make contact with the bottom of the kettle. They are a safety feature to disconnect the power when the kettle gets too hot.

[@anonymnect]

hey man i have a problem kettle turns off within 3 seconds, thank you very much for the video, you explained very well what the problem is 😀👍

[@ScottiesTech]

It's probably that little metal strip that's tired.

[@Gardien48]

Thxs. I had repaired a kettle Rüssel hopes. It was o proplem with the switch. Now it works again. Only the power led which is integrated in the switch does not light. Two wires from this led are connected to the header element. Do you know how this works?

[@ScottiesTech]

Well, the LED needs DC, so either there is some AC -> DC adapter somewhere, or more likely it's a self-contained LED bulb + basic electronics to rectify the AC into DC and power the LED. OR... Are you sure it's a LED and not a little weird-lookin' neon lamp?

[@Toyrapy]

Very informative in an entertaining way... thanks for sharing!

[@meenusachdeva]

Can we remove this metal tip to remove autocut function?

[@adrianpoly]

good video man, just wondering why my kettle won't turn on sometimes, light flickers on and off in the on position. guessing it was just a loose connection but took the kettle apart and blew my mind when opening it, henceforth, i gave up.

[@allenvanhellen2572]

adrian polydorou Try cleaning all the contacts on the base and on the bottom of the kettle itself with sand paper and then vinegar.

[@Slim-Pasty]

Kettle in family home will not auto switch off. I check the biometric disc (beneath the switch), it's fine. It flexs when heated and fully connects with the switch, yet will not trigger the switch when powered on. Kettle water just boils, boils, and boils away, rocking and shaking. Steam wand inside is not blocked and channels well onto the biometric disc (lid is on/shut). Completely perplexed with the unit at this point 😦😕.

[@1Dont-ask1]

THANKS FOR THIS VIDEO! Now I can explode the kettle without it turning off! No but rlly thanks for this video! This helped as my kettle was not turning off! So now I can replace it! :p

[@PinkyPink2362]

thanks so much! this was really informative

[@chachiye4679]

Great video. Where to buy this bimetallic strip? I cannot find it.

[@ScottiesTech]

Not sure... They seem to be custom made for each different kettle.

[@Happy_Harry]

Can that bi-metalic strip wear out over time by eventually requiring more heat than before to trip the switch? Seems like mine doesn't want to shut off anymore.

[@erinkintzing879]

I am having the same issue!

[@Happy_Harry]

@@erinkintzing879 I have found that my lid hinge plastic weakened over time from the heat causing the hinged lid to not fully close. This allowed excessive heat/steam to escape from the top of the kettle causing the bi-metallic trigger to not trip. Put a weighted object on top of the lid to hold it down fully and see if it trips off. If it does, then most likely that is your problem.

[@naderiskandar1896]

Perfect explanation ! Thanks a lot

[@collinjohnsonnaidoo3577]

Good stuff. Presently having problems with Morphy Richards kettle not switching off. What source of heat triggers the bi metal strip . Thanks

[@zytigon]

If the manufacturers tweaked the kettles to switch off at 90 Celsius would it save much electricity ? I see it is possible to buy expensive kettles with options to switch off at different temperature but they seem to depend on electronics that some claim malfunction sooner than normal kettles - like you mention at end of your video.

[@ScottiesTech]

I suppose that would save some juice. The heating element would consume the same amount of power, but every kettle wouldn't run as long, thereby adding up to a lot of saved kWh. But then you might even up with a lot of grumpy tea drinkers, which could be dangerous...

[@stevec9669]

I have a teapot like that. Somehow that switch keeps tripping before the water reaches boiling point. It was not like this when it was new. Can I rewire it and bypass this switch and manually shut it off when the water is boiling?

[@ScottiesTech]

Yeah, if you want. Just don't forget it and let it boil forever, cuz eventually something will melt.

[@nskmda]

Genious... i always thought there would be some thermal relay element which would be extremely complicated... anyway, my question here is: what could be a reason for my kettle to... like... 'pause'... it doesn't turn off via the bimetal plate, no. it looks like it 'stalls'. you can hear that sound of water warming up then it stops for a second or 2 (the sound dies down) then 'turns on' again and keeps warming the water up. eventually it does boil it but now it takes about 15 min vs normal 2-3 min. what might be the reason?

[@ScottiesTech]

Hmm... Maybe it has one of those thermal 'fuses' that open when it overheats? Sometimes they go bad and open early, then close again when it cools off. That's pretty weird, tho...

[@destino3034]

Is it safe to take the strip off? I want to boil for longer periods

[@ScottiesTech]

Well, just don't let it run forever. Eventually, it'll boil over - and probably some parts will start melting.

[@TTOQ1]

I have a project, and I need to make a circuit that turns a kettle off at 75°C , soo how would I do that, pls help me

[@ViciousPikachu]

My kettle keeps shutting off and on and also the food always burns and sticks to one half of the side but the other half doesn't get anything stuck on it and seems like the other half is not hearing up.

[@Mike-me3sp]

You forgot to explain how that bimetal strip actually gets hot, since it's just sitting in the cavity under the kettle and is not actually in contact with anything but the plastic molding.

[@briquebrune]

What if my kettle has stop turning off when the water is ready?

[@tr3nchify]

Do you know the maximum Temperature that it can handle?

[@nekohanyougirl]

Cool info! Thanks for the vid

[@maheenshahab8859]

I bought a new kettle, idk why I boiled milk in it yesterday but I did and now the temperature sensor thing isn't working fine... I'm so sad. It turns off when water is just lukewarm. Sometimes i cam manually try to press the button and it ends up boiling and sometimes the button doesn't even go down even though water isn't boiled yet. Can you help me what can I do 😭

[@ScottiesTech]

Well, that's odd... I wonder if it works differently than the one I showed here? Even do, you'd think heating pure water in it would clean it out well enough. Maybe heat some soapy water, rinse, and try again? I really have no idea...

[@garagekeys]

Thank you, good video

[@rohithkandukuri]

My teacher recommended to me to watch this

[@saarike]

Nice video!

[@olivierblouin5326]

I have a vintage Alessi electric Kettle with a whistle on it. Sadly, the automatic switch turn off too quickly so I never hear the whistle. Is there any way to change the bimetallic switch for a more resistant one in order to hear the whistle when the water boils? Thanks.

[@ScottiesTech]

If you can find the specific strip for that kettle... Which is a tall order!!!

[@olivierblouin5326]

@@ScottiesTech I'll dismantle it to find out. See where this leads me. Thanks

[@terrypearson6801]

Great vid Scottie. As our kettle boils for quite a few seconds before it turns off, I often flick the switch off when it first boils, but my wife says "don't, you'll break it!" Will my doing that cause any problems? Also, what is the reason for the manufacturer saying their must be a minimum level of water in a kettle - apart from the obvious thing that if there is a ridiculously small amount there's a danger of it burning out??

[@ScottiesTech]

Turning it off early shouldn't cause any problems. It just manually flips the mechanical lever instead of it being automagically triggered by the bimetallic strip. As for the minimum water, that's a good question! Being a rebel, I've tried running the kettle with less than minimum water, and it works fine. Even if there's no water, it should still shut off fairly quickly, and that's that... Another mystery to solve!

[@Diandredofus]

@@ScottiesTech Pretty sure they ask you not to run it with less than minimum water because there's a delay between the water boiling and the kettle turning off. If you run it with minimal water, there's a chance all of the water boils before the kettle turns off, which means the heating element will be heating a dry plate. The plate is definitely not designed to get warmer than a specific temperature, and without any water to absorb the excess heat you're bound to melt some plastic.

[@prabjyoti4392]

Can we remove the bimetal ...??

[@wednesday567]

Can i plug a kettle into a power strip extension? Does it draw alot of power?

[@ScottiesTech]

Yes, but... You can almost always plug things into power strips without any danger - if only 1 thing is running at a time. What you can't do is plug several high-power gizmos (like kettles) into a power strip and use more than 1 at a time.

[@alphawolf0601]

God it bruh! Thanks for the knowledge.

[@alphawolf0601]

I found this video too late lol. I was actually fixing this part of my kettle and found it a little bit rusty. So I put out my Dremel and sanded most of the rust. So now, some part of the metal was rubbed off and and not flexing anymore. Guess I learned the hard way

[@RamziiMazi]

how can i make a kettle energy saver and what do i need

[@ahmad-ali14]

thanks, interesting vedio

[@muralidharbayar3097]

I want a switch...pls..give me the link

[@Thebiggame-dc8ek]

the button doesn't sound click and the kettle doesn't turn on. I opened the buttom of the kettle and see that the button can't move the mechanism as it should😢

[@spaceman51974]

hey Einstein, water boils at different temps at different altitudes. So, I guess on mount everest it would just never turn off??

[@ScottiesTech]

See here: scottiestech.info/2017/06/28/how-does-an-electric-tea-kettle-know-when-to-turn-off/#comment-511811

[@ScottiesTech]

@Zero Cool No steam tube in mine...

[@MSTECHCHANNEL]

good video

[@utoopuser]

FYI: The bi metal thermal spring shown here is for the ULTIMATE disconnect, when the kettle runs dry.( for safety, not for control) Another youtube tutorial shows the thermal switches for control at boiling point. They are close to the hot plate. kzbin.info/www/bejne/oXWaapSJbdqqjZY

[@Mike-me3sp]

Thankyou. This guy seems to have forgotten to explain the step of how this bimetallic strip actually gets hot.

[@terencem9962]

I was a front runner in developing the 'Automatic water boiler' - i refuse to call it a kettle cos i HATE that guy. And i had the better product - i had a tri metalic strip and it would automatically turn itself on when it got too low of a temperature outside (cos that's when people need their tea isn't it!) and then it would automatically turn itself off after it had boiled the water for you. Jeremiah C Kettle did me very dirty and stole the idea i had for the trimetallic strip and since he was trying to do it on the cheap he just went with two layers - clearly an interior product to mine but since his product came out that little bit cheaper he won the race and now everyone has been robbed of having a nice warm kettle waiting for them whenever it gets too cold. I will never forgive that man.

[@karengt3052]

My switch isnt staying down on its own i have to put a little weight to keep the switch down for the water to boil how can i fix this

[@ScottiesTech]

Have to take it apart and investigate. Could be some little plastic bit broken off, or possibly the bimetallic strip thingy is worn out and always in 'turn off' position.

[@karengt3052]

@ScottiesTech hey I have some good news I took it back apart and heat the little circle metal plate only to realize it's not moving so I removed it and the kettle switch is working again just that I have to click it off. But that's great better than having to put something on the switch for water to boil 😊 thanks for your video. If you know where I can purchase the plate let me know 🙏

[@jonathanbispat5848]

how do i fixed it?

[@shivamshrivastava7739]

Can i remove it for not being off

[@viveks4186]

Could have done bit faster....

[@yarzarm]

Thanks

[@emadsaleh8311]

How can we mend it ..

[@brianbirish]

My kettle takes a long time to finally shut off. 30 seconds or more. Lots of steam. Guess there is nothing I can do

[@erichmartin8534]

why not turn off when lid is open?

[@EpulKuat]

I came here after i boiled my water... best with 1.5x speed

[@Dearjohn999]

That looks well set up think it’s for real 😂

[@ScottiesTech]

You mean my little workstation? Never underestimate the power of OCD...

[@rickguy2006]

6:27 brrr tapabree breeebule brrrrr, thanks for watching :D

[@dialing1111]

Came form Integrated Science homework 😢

[@oldguy8177able]

yes very good you nearly fried your kettle

[@sweetblues3230]

I actually I came here cause of automatically turning off.because I cook rice

[@maryamazha1357]

damn you so cool

[@lizanne6187]

Blasphemous git.