UK Kettle Element Keeps Blowing

[radiohead]

I'd bet on it being either coincidence, cheap kettles or boiling dry. The same complaint often comes up with lighting.
"The lamps keep blowing, must be a wiring fault"
There never is, it's always rubbish lamps.
And as stated above, there is no wiring fault that's going to kill a resistive load, I wonder as well if the OP has actually verified the element is at fault each time, could be .a different issue with each kettle

 

[freddo]

a poor neutral connection on the supply transformer could possibly be causing the voltage to the property to float up to 400v.

I'd guess a kettle would last a lot longer at 415 volts than most of the other appliances in the house! I'm struggling to think of a fault in a kettle element that would trip the MCB and not the RCD as well.

 

[davesparks]

5. The heating element of the kettle gets damaged

What is the damage and how was it identified?
Are these kettles available for inspection?

Do you have any evidence other than what the tenant has told you?

 

[static zap]

As well as under filling , some designs can be more prone to "Flash over" Bang heard-Phut-
Over filled /angled while filling !
-Not a tesco's white special ,but Morphy Richards-
(Washing up present in sink = Kettle at a funny angle)
--mine took out MCB but not fuse ! --

 

[Zerax]

What is the damage and how was it identified?
Are these kettles available for inspection?

Do you have any evidence other than what the tenant has told you?

Good points... and... do both the Landlord and tenant have alibis for the times when the alleged kettle failures happened ?

 

[dmxtothemax]

Are you sure it's not a genuine circuit overload ?
It's very easy to over load a circuit with out knowing
perhaps there's more on this circuit than you realise.
and also consider the fact that he may be using cheap chinese graded stock !

 

[ImpededLoop]

Are you sure it's not a genuine circuit overload ?
It's very easy to over load a circuit with out knowing
perhaps there's more on this circuit than you realise.

That's a good question. Does the tenant try the kettle again after the mcb has been reset? It could be too many appliances switched on and the kettle is the final appliance used that causes the mcb to operate.

 

[electric al]

Overload of the circuit is my guess and the plug fuses blowing and an assumption the kettles are dead

 

[DPG]

Overload of the circuit is my guess and the plug fuses blowing and an assumption the kettles are dead

But if the circuit is overloaded why would the appliance fuses blow?

 

[static zap]

5. The heating element of the kettle gets damaged

This fault defies logic ,unless other appliances can survive over voltage!
a) Is the kettle the only appliance plugged in the kitchen?
b) Is it a block of flats with 3 phase ?
c) Possibly another high demand device like a shower finding a weak neutral. ..any complaints of a missbehaving shower (else where in building) !
d) The alleged dead kettles are they quality -or cheapies ?
(punting for a posh one - to Boast about on social media !)

 

[marconi]

Re Buzzlightyear's #7 - reversed polarity:

I've been mulling over Buzzlightyear's interesting hypothesis . It would have a possible association with the recent swap of consumer unit; before it all was well and afterwards it was not in the lives of kettles. And there is a further consequence of reversed polarity - the wire element will spend most of its life at mains potential which in turn means the insulation around it and encased by the metal casing is permanently subject to mains voltage electric field. This electric field is the same magnitude (240V rms, 350V peak) all along its length. For the brief periods the element is on to heat water, the electric field will be tapered from 240/350V at the line end to 0V at the neutral (and now switch) end. With correct polarity there is no electric field for the vast majority of the day and when used it is only a tapered electric field.

With reversed polarity there would be then a change in the electrical stress on the element and in particular its insulation. Maybe then the insulation is breaking down because of the unusual prolonged mains electric field? eg partial discharge - at a place or places along the wire element? Over time this earth fault current combined with the LN current is high enough to trip the mcb (but which mechanism thermal or magnetic?). Depending on the overcurrent it is not unknown for mcbs to trip before a 13A fuse ruptures.

Partial discharge - Wikipedia - https://en.wikipedia.org/wiki/Partial_discharge

Why most often first thing in the morning? Because at this time the element has spent the longest time energised for partial discharge (or something else) to begin to form a tracking path to earth for a low leakage current to begin with which eventually breaks down under the influence of heat for a significant flow of current. The rcd does not trip (it is stated #1) perhaps because the tracking only causes a small earth leakage current to begin with - though I would have expected both the mcb and rcd to trip when the element's insulation eventually failed catastrophically - so I admit my theory does not fit well if the rcd stays closed.

The long and the short of it then is I would check the polarity of the supply at the socket the kettle normally uses and while at it in the CU too.


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For the Landlord - does the mcb trip when the kettle is first turned on or during the heat cycle?

 

[Zerax]

Overload of the circuit is my guess and the plug fuses blowing and an assumption the kettles are dead

Very true... we need to see copies of the autopsy reports on those kettles ! And if they've already been buried... exhumation orders to follow... I wonder what the 'boys back at the lab' would uncover ? (aka Lucien & Marconi)

 

[Lucien Nunes]

Any kettle sold in the EU should operate correctly with arbitrary polarity, since some countries use non-polarised plugs. Sheathed heating elements are not unlike MI cable, just with a nichrome spiral in place of copper conductors. Although the ultimate breakdown voltage of MI is sometimes lower than a polymer-insulated cable, it is unlikely to be affected by continuous connection to the line.

 

[electric al]

Very true... we need to see copies of the autopsy reports on those kettles ! And if they've already been buried... exhumation orders to follow... I wonder what the 'boys back at the lab' would uncover ? (aka Lucien & Marconi)

I concur zap - forensic reports and toxicology tests undertook by our very own lab boffins could be an entirely different kettle of fish
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Zerax even

 

[freddo]

But if the circuit is overloaded why would the appliance fuses blow?

The fuses aren't blowing according to post #1

 

[DPG]

The fuses aren't blowing according to post #1

True but post 28 suggested that an overload of a circuit could cause appliance fuses to blow.

 

[static zap]

Re Buzzlightyear's #7 - reversed polarity:
I've been mulling over Buzzlightyear's interesting hypothesis .

I'm still pondering another angle.
(that would require a 3kW isolation transformer and MFT to investigate)
Paper would be-Entitled
"Poor IR situations in re-boiled over filled modern auto off Kettles & and possible metallic sputtering of contacts onto plastic in a confined streamy enviroment. "
-- I do enjoy a good think --

( previously tasked with "re-animating" a few from the grave-by Mr Frugal)

 

[electric al]

I'm still pondering another angle.
(that would require a 3kW isolation transformer and MFT to investigate)
Paper would be-Entitled
"Poor IR situations in re-boiled over filled modern auto off Kettles & and possible metallic sputtering of contacts onto plastic in a confined streamy enviroment. "
-- I do enjoy a good think --

( previously tasked with "re-animating" a few from the grave-by Mr Frugal)

I think all your paper requires zap is a couple of algebraic equations in order for it rock the scientific establishment. I'm certain our resident boffins could come up with something that would prove something even if it's only that equations make my head ache

 

[radiohead]

I cant help thinking there's too much thinking going on here.

 

[pirate]

Just for information,here in Spain, if the power fails, it's almost always the kettle.
That's because of the cal, because the water isn't that good. So whenever the power goes down, we unplug the kettle, and everything works again.
Just saying...