Bizzare double failure in oven

We have a fancy Fisher & Paykel double oven, all the way from NZ. Both ovens have multiple elements, and both are fan ovens. We usually use the ovens in fan mode, which uses a circular element at the back, around the fan blades.
The oven is around 3 years old, and I have already had to replace the circular element on the lower oven a year and a half ago.
This afternoon, we had set dinner in the main oven on a timer, whilst we were out.
When we got in, oven dead, MCB tripped out, no dinner. Re-setting MCB - big flash in MCB, tripped out again, Hmm. Turn oven off, re-set MCB OK. Try other elements on oven. OK. Try fan element again ( expecting MCB trip ), nothing, no trip, no heat. Diagnosis: stuffed element, shorted as it died, fault now self-cleared. Fair enough. Will investigate later.
Decamp dinner to lower oven, cooks OK. We go to make some other stuff to have for midweek, and mid-way through cooking, bang. MCB trips, oven off again. Double Hmm.
Time to investigate. I'm concerned there's some other fault, not just a dead element. I'm not a great believer in co-incidences.
However, it does indeed appear that both elements have died identically within hours of each other. Bizarre. Each has a small melted hole at the point of failure ( as often happens ). Each is now open-circuit end-to-end ( and also to earth ).
The ovens were not overheating. Check my computer UPS logs: there was no over-voltage incident logged.
Just a random near-simultaneous failure. Odd, but there you go.
--
Ron





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Ron Lowe <ronATlowe-famlyDOTmeDOTukSPURIOUS> wrote: [snippage]

Any chance there is a common air inlet to the fans, which has become blocked?
There would be no cooling airflow across the elements, so they could hotspot and fail.
No airflow could also be the reason why the ovens were not apparently overheating.
--
Tony Williams.

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Fans in ovens recirculate the air in the oven so if it were blocked the food wouldn't cook. Also the ovens have separate air flow paths so they can run at different temperatures.
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"Ron Lowe" <ronATlowe-famlyDOTmeDOTukSPURIOUS> wrote in message

It'll be a foreign cooker with 230V elements running at 250V UK, My mate had an expensive huge Smeg double cooker and both oven elements blew up within days of each other after about 18months. 2nd failure probably caused by using the smaller oven a lot more whilst big oven out of order.
Anyway the replacement elements he got had 240V stamped on them as opposed to 230V on the original ones. He lives in the country and frequently has mains rising to 250V at certain times of the day. That was about 3 years ago, the replacements work fine.
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Well, That seems to be the case here too..
The failed elements were stamped 2500W @ 230V. ( One was an original, the other was a replacement ) So they would be running at a slightly higher wattage on 240v. ( Around 2600W )
The replacements ( Genuine Fisher+Paykel ) are stamped 2400W @ 240v, so a double down-rating.
We'll see if it makes any difference.
My mains is fairly stable now, after a period of outages, brownouts, and overvoltages a couple of years ago. The server UPS is less essential than it was.
--
Ron



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I can't think that running a "nominal 230 Volt" rated heating element at even 250 volts would blow it up - it would only run a bit hotter Nick
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"Ron Lowe" <ronATlowe-famlyDOTmeDOTukSPURIOUS> wrote in message

Didn't UK voltage go down to 230 years ago, the same time euro voltage went up to 230 from 220?
--
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Only nominally, not in practice. It was a fudge by tollerance-change, so everyone is harmonised without anyone having to change anything.
We could harmonise with the US too, if we described our mains voltage as 230+/- 60%!
--
Ron


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Ron Lowe wrote:

It's a shame we couldn't have done the same with wiring colours - designated brown as a range of colours that happened to include red. I suppose it would still leave us with the black (N) vs black (L) problem though.

And have even more American tourists setting fire to their hair trying to use their curling tongs on British electricity :-)
Owain
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Yeah, well give or take a few percent in the tolerance.
(They changed the voltage tolerance to keep 240v acceptable.)
--
Clive Mitchell
http://www.bigclive.com
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