kettle not boiling ??

[sparky1505]

Any thoughts?
One of my customers has a new kettle but every time he plugs it in to boil it always switches off before it boilling. He has changed the kettle and the new one does the same.
He changed the kettle for a diffrent make and that does the same .
He has tried the kettle in a different property and the kettle boils perfect.
The property has been recently re wired and the ring final circuits are wired in 4mm. All tests are good voltage is 240.3v and drops to 239v when kettle is on, so no problem with the voltage am i missing something?

 

[wingcoax]

He does'nt live down a deep hole does he? This sounds like a question from my schooldays science classes.

 

[tonyelectric]

Has he tried it in other sockets?, are you measuring the voltage from the back of the socket (my thinking being dodgy contacts in socket) - odd one certainly

 

[sparky1505]

Deep hole maybe we are in Wales. and am checking the voltage by plugging in the tester in the same double socket. definetaly a tricky one

 

[bernardgreen]

Is there anything unusual about the water in the house ?

It might be there is a lot of dissolved air coming out of solution and this hot air is tripping the automatic switch off mechanism that would normally be tripped by steam

Or there is a lot of minerals dissolved in the water raising it's boiling point above normal. Water drawn from a well may have a lot of dissolved minerals.

 

[sparky1505]

thats great thanks, sounds like the problem. the water does come from a well so the water could very well be the problem.

 

[wingcoax]

If BG is right, i wasn't too far off the mark then.

 

[ColJack]

or he could live on a high mountain ( doesn't the boiling point drop at higher altitudes meaning it "boils" at a temp lower than 100°C ? )

 

[wingcoax]

Sorry CJ, You are correct. It is a long time since science classes

 

[ColJack]

you were right too..

if you are down a deep hole then the increased pressure means that it wouldn't boil until it's over 100°, and if that's when the trip cuts off then it wouldn't bubble before it's technically boiled.

 

[ricicle]

At lower atmospheric pressure (eg high altitude) the water will still boil but at a lower temperature. That is why it is difficult to make a decent cup of tea as the water is not hot enough to disperse the tea flavour properly.

 

[johnnykc]

Water will boil at 71 deg C on the summit of Mount Everest (8848 metres)......

Is your house on stilts on Snowdon?










:

 

[Mursal]

Would it be worth measuring the voltage across the element with the load (Kettle) connected?

This way any bad connection in the circuit when under load would show up as a voltage drop.

 

[IJWS15]

Remembering my thermodynamics this has to be something to do with the water . . . .

What did he use before he bought this kettle - an old non "automatic" one?

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 and if you take the Everest example an automatic kettle would boil dry before it switched off as the water vapour/steam mix would never exceed the boiling point at that pressure. My wife does not believe me when I tell her than a pan of waer does not get any hotter if it is boiling more vigorously - at STP water cannot exist above boiling point, it turns to steam.

If the supply or the kettle was at fault the kettle would not heat the water or would not swich off.

As he has already tried 2 kettles tyr the kettle that won't boil with water from a different source.

Another example - 2 weeks ago our car was parked outside my father's home near Barnsley overnight, 6.5c below at 09:30 Sunday morning. The bottle of Teesside tapwater im the drivers door was frozen, the bottle of Evian in the passenger door was not.

 

[DetlefSchmitz]

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.