kettle not boiling ??

[ban-all-sheds]

Indeed, and every kettle I've ever owned wouldn't cut out at all (or if it did not for a randomly very long time) if you left the lid off or held it open.

It would merrily boil away.

Definitely needs a build up of steam inside to work the cutout.

 

[DetlefSchmitz]

So the excess dissolved gas theory has a lot going for it. It might convey heat to the bimetal strip prematurely as it is driven off.

 

[ricicle]

To prove the water theory fill the kettle up from the house where it worked and then bring it to the dodgy house to boil

 

[ban-all-sheds]

And/or vice versa.

 

[bernardgreen]

Bit of care needed.

Transporting the well water might allow any dissolved air to come out of solution before getting to the kettle. Take some tap water to the kettle for the test. Then try fresh well water in the kettle.

Take tea bags as well ( pun not intended ).

 

[sparky1505]

Thanks for all your posts guys . reading every thing i am confident it is the water. going to do the test next week with different water (will remember the tea bags)

 

[ban-all-sheds]

Just don't tell anyone you're going teabagging...

But on a serious note, if it does turn out to be the water your customer really should get it analysed, just in case whatever is in there is Bad Stuff.

 

[TicklyT]

How full is the kettle each time?
IME the cutout operates faster if a kettle is filled to it's maximum capacity than if it is just filled to the minimum mark.

 

[ColJack]

at STP water cannot exist above boiling point, it turns to steam.

yes it can..

if you microwave a cup of distilld water you can super heat it to more than 100°C and it doesn't boil...... until you drop a sugar cube or spoon etc into it.
they did it on mythbusters...

 

[bernardgreen]

If you repeat this experiment take great care.

The super heated water can turn to vapour at the slightest disturbance. Even the air vibration from a loud noise can trigger the evaporation process.

Evaporation occurs throughout the liquid and is akin to an explosion.

This can result in scaldingly hot water being thrown out of the cup and serious burns are possible.

 

[chappers]

All kettles are set to switch off at around 100C as that is when water boits at standard temperature and pressure - say 20C and 1 bar (atmospheric). The setting on the kettle is absolute

Certainly all the kettles I have ever owned worked differently. The automatic switch-off bimetal strip is installed outside the kettle, in the handle moulding, and seems to be set to a non-critical temperature well below 100°C. When the kettle boils, steam is directed through a hole in the lid to the external sensor which causes the switch-off. So switch-off is related to the boiling event, not te actual temperature.

I can't imagine a sensor being accurately enough made to simply sense the water temperature as being exactly 100°C, it simply wouldn't be precise enough.

No the bimetallic switch is definitely related to temperature, but as it is remote from the water, it doesn,t have to itself reach 100 degrees just a temperature that coresponds to the water in the kettle boiling, the closer to the boiling water the closer to 100 degrees it will operate at.
If for example the steam was directed down a 1 meter tube to the switch and at that point the steam was only at 50 degrees whilst the water was boiling then the switch would only have to operate at 50 degrees to cut out whilst the water was boiling.
The switch isn't that sensitive thats why the water usually boils for a while before the switch heats up to its cut out point(whatever that is)

 

[DetlefSchmitz]

I wish I'd said that. Oh, wait a minute...

 

[IJWS15]

at STP water cannot exist above boiling point, it turns to steam.

yes it can..

if you microwave a cup of distilled water you can super heat it to more than 100°C and it doesn't boil...... until you drop a sugar cube or spoon etc into it.
they did it on mythbusters...

Not tried that (would not want to at home) but how do you know it is over 100 C? The implication is that inserting a thermometer would cause it to boil. Do you believe everything you see on TV?


To me a superheated fluid means it has been heated above its "natural" state by increasing the pressure, release the pressure and it gets interesting. BTW steam is a fluid as is water, steam is invisible, water vaopur can be seen (and no, water vapour is not steam, it is small droplets of water in the air, steam is evaporated water.) vapuoinstantaneous boiling.

Superheated liquids are VERY DANGEROUS

 

[Monkeh]

at STP water cannot exist above boiling point, it turns to steam.

yes it can..

if you microwave a cup of distilled water you can super heat it to more than 100°C and it doesn't boil...... until you drop a sugar cube or spoon etc into it.
they did it on mythbusters...

Not tried that (would not want to at home) but how do you know it is over 100 C? The implication is that inserting a thermometer would cause it to boil. Do you believe everything you see on TV?


To me a superheated fluid means it has been heated above its "natural" state by increasing the pressure, release the pressure and it gets interesting. BTW steam is a fluid as is water, steam is invisible, water vaopur can be seen (and no, water vapour is not steam, it is small droplets of water in the air, steam is evaporated water.) vapuoinstantaneous boiling.

Superheated liquids are VERY DANGEROUS

And that's precisely what can happen in a microwave. Surface tension can prevent water from boiling. And you don't even need distilled water.

 

[echoes]

This reminds me of a chemistry lesson I still remember where we were boiling a beaker of ethanol. Mine wasn't boiling, so the teacher stuck a thermometer in, at which point the whole lot boiled violently, splashed everywhere and caught fire.