10+ year old Neff oven, just decided to trip RCD, no previous trouble.

99% of the time it's used in fan mode (where the element used is within
the fan).

Just went to use it in a different mode where top and bottom elements
used, but not fan, it had been heating up for a couple of minutes then
tripped the RCD in its half of the CU.

Hoped it was a one-off, so reset and tried again, tripped again,
wondered if the internal light was causing it so removed bulb, still
tripped.

Each time after resetting RCD have to prod the timer button to "ack" the
mains failure, then the electronics are on (i.e. clock flashes) if the
main selector knob is "off", it doesn't trip.

If I turn temperature knob to coldest, I can turn the selector knob to
the setting where just the internal light is on, it doesn't trip (a
small cooling fan also runs)

Leaving selector knob in the internal light setting (i.e. no elements or
main fan) then turning up the temperature knob it trips the RCD as soon
as I hear the stat click on.

To me that doesn't scream "earth leaky element" but rather "gunge has
got into stat or across some wiring"

Thoughts?

Andy Burns used his keyboard to write :
10+ year old Neff oven, just decided to trip RCD, no previous trouble.

99% of the time it's used in fan mode (where the element used is within the
fan).

Chances are, it is the element which is in use, which is failing and
causing the trip. If the particular element can be seen, carefully
inspect it and you might see some obvious signs of damage.

On 17/12/2017 14:08, Andy Burns wrote:
10+ year old Neff oven, just decided to trip RCD, no previous trouble.

99% of the time it's used in fan mode (where the element used is within
the fan).

Just went to use it in a different mode where top and bottom elements
used, but not fan, it had been heating up for a couple of minutes then
tripped the RCD in its half of the CU.

Hoped it was a one-off, so reset and tried again, tripped again,
wondered if the internal light was causing it so removed bulb, still
tripped.

Each time after resetting RCD have to prod the timer button to "ack" the
mains failure, then the electronics are on (i.e. clock flashes) if the
main selector knob is "off", it doesn't trip.

If I turn temperature knob to coldest, I can turn the selector knob to
the setting where just the internal light is on, it doesn't trip (a
small cooling fan also runs)

Leaving selector knob in the internal light setting (i.e. no elements or
main fan) then turning up the temperature knob it trips the RCD as soon
as I hear the stat click on.

To me that doesn't scream "earth leaky element" but rather "gunge has
got into stat or across some wiring"

Thoughts?



Screams to me knackered element.

The stat has to be switching something.

--
Adam

Harry Bloomfield wrote:

Chances are, it is the element which is in use

Except it happens when no elements are in use, when the fan element is
use, and when the top/bottom elements are in use, which is what leads me
to think it's not element related.

which is failing and
causing the trip. If the particular element can be seen, carefully
inspect it and you might see some obvious signs of damage.

Now it's cold again, I'll degunge it and see what happens

ARW wrote:

Screams to me knackered element.

I suppose an oven tripping normally would scream "element" to me,
especially using one that hasn't been used for some time.

But what tempts me to think otherwise is that with the control knob in
the "light" position it still trips; so it trips regardless of whether
no element, fan element, top element, bottom element, top and bottom
elements are selected ...

The stat has to be switching something.

Do they tend to have an actual stat, or a thermocouple that operates a
relay? You can certainly hear something click at the set point.

Double pole switching? then I suppose a fault from the neutral "end" of
end element to earth would do it, even for an element that wasn't in use.

Andy Burns expressed precisely :
Except it happens when no elements are in use, when the fan element is use,
and when the top/bottom elements are in use, which is what leads me to think
it's not element related.

Ah, OK. Remember a neutral leakage to earth can also trip an RCD.

On 17/12/2017 14:48, Andy Burns wrote:
ARW wrote:

Screams to me knackered element.

I suppose an oven tripping normally would scream "element" to me,
especially using one that hasn't been used for some time.

But what tempts me to think otherwise is that with the control knob in
the "light" position it still trips; so it trips regardless of whether
no element, fan element, top element, bottom element, top and bottom
elements are selected ...

The stat has to be switching something.

Do they tend to have an actual stat, or a thermocouple that operates a
relay?Â* You can certainly hear something click at the set point.

Double pole switching? then I suppose a fault from the neutral "end" of
end element to earth would do it, even for an element that wasn't in use.

Sure that you are not turning on the grill:-)?

The oven will use a thermocouple IMHO

Ovens are complicated things and best left for women to use.

Although they are usually **** easy to fix.

Depending on your make and model it's often only about 10 minutes work
to gain access to the elements terminals and do a LE resistance test or
disconnect the elements one by one and see what happens.


--
Adam

On 17/12/2017 14:48, Andy Burns wrote:
ARW wrote:

Screams to me knackered element.

I suppose an oven tripping normally would scream "element" to me,
especially using one that hasn't been used for some time.

But what tempts me to think otherwise is that with the control knob in
the "light" position it still trips; so it trips regardless of whether
no element, fan element, top element, bottom element, top and bottom
elements are selected ...

If the element has a neutral to earth short, it can trip the RCD
regardless of whether its being used or not.

The stat has to be switching something.

Do they tend to have an actual stat, or a thermocouple that operates a
relay? You can certainly hear something click at the set point.

It will have an actual stat of some form...

Double pole switching? then I suppose a fault from the neutral "end" of
end element to earth would do it, even for an element that wasn't in use.

Indeed.

Can you isolate the cooker and do a neutral to earth resistance check?


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

ARW wrote:

Ovens are complicated things and best left for women to use.

That's why I mostly leave the oven on "fan", same as I mostly leave the
washing machine on "synthetics" :-P

Although they are usually **** easy to fix.

Depending on your make and model it's often only about 10 minutes work
to gain access to the elements terminals and do a LE resistance test

From youtube videos, it seems the oven probably needs to come out of
the housing to access the top and bottom elements.

John Rumm wrote:

Andy Burns wrote:

Double pole switching? then I suppose a fault from the neutral "end" of
[the] element to earth would do it, even for an element that wasn't in use.

Indeed.

Can you isolate the cooker and do a neutral to earth resistance check?

Yes, combined DP cooker switch/socket nearby ...

On Sunday, 17 December 2017 14:37:25 UTC, Andy Burns wrote:
Harry Bloomfield wrote:

Chances are, it is the element which is in use

Except it happens when no elements are in use, when the fan element is
use, and when the top/bottom elements are in use, which is what leads me
to think it's not element related.

which is failing and
causing the trip. If the particular element can be seen, carefully
inspect it and you might see some obvious signs of damage.

Now it's cold again, I'll degunge it and see what happens

Probably the clicking thing feeds one end of the element and the control switch the other. It's still most likely a bad element.

There isn't any more anyone can tell you, it's time for you to either test the elements or power it up without RCD to dry them out. Proper earthing is essential for the latter of course.

James Wilkinson Sword wrote:
On Sun, 17 Dec 2017 14:08:32 -0000, Andy Burns
wrote:
10+ year old Neff oven, just decided to trip RCD, no previous
trouble. 99% of the time it's used in fan mode (where the element used is
within the fan).

Just went to use it in a different mode where top and bottom elements
used, but not fan, it had been heating up for a couple of minutes
then tripped the RCD in its half of the CU.

Hoped it was a one-off, so reset and tried again, tripped again,
wondered if the internal light was causing it so removed bulb, still
tripped.

Each time after resetting RCD have to prod the timer button to "ack"
the mains failure, then the electronics are on (i.e. clock flashes)
if the main selector knob is "off", it doesn't trip.

If I turn temperature knob to coldest, I can turn the selector knob
to the setting where just the internal light is on, it doesn't trip
(a small cooling fan also runs)

Leaving selector knob in the internal light setting (i.e. no
elements or main fan) then turning up the temperature knob it trips
the RCD as soon as I hear the stat click on.

To me that doesn't scream "earth leaky element" but rather "gunge has
got into stat or across some wiring"

Thoughts?

Remove the RCD. Oh how simple life is with fuses....

That must be the stupidest thing you have ever come out with, Birdbrain.
What a fool you really are.

wrote:

There isn't any more anyone can tell you, it's time for you to either
test the elements or power it up without RCD to dry them out. Proper
earthing is essential for the latter of course.

Yeah, I was thinking the thermostat would be single-pole, but I think
it's reasonable to assume from the behaviour it's double-pole with the
switched neutral being common to all elements.

After it cooled down completely, I tried it once again and it did switch
on for several seconds before tripping, so all it needs now is to check
which of the three elements it is that's ****ed, unfortunately I think
that requires removing the whole oven, rather than slipping the elements
out from inside the cavity, at least all spares are available.

On 17/12/2017 15:21, Andy Burns wrote:
ARW wrote:

Ovens are complicated things and best left for women to use.

That's why I mostly leave the oven on "fan", same as I mostly leave the
washing machine on "synthetics" :-P

Although they are usually **** easy to fix.

Depending on your make and model it's often only about 10 minutes work
to gain access to the elements terminals and do a LE resistance test

From youtube videos, it seems the oven probably needs to come out of
the housing to access the top and bottom elements.

Check the fan.

In a previous fan oven, we had a problem with 'gunge' collecting on the
fan. I'm not suggesting your oven is dirty- the fan is tucked away and
not normally cleanable as part of the normal regime.

A quick clean, and all was well.

Our current oven is 'self cleaning' but I still half expect that, it
time, the fan may need a clean.

On 17/12/2017 14:08, Andy Burns wrote:
10+ year old Neff oven, just decided to trip RCD, no previous trouble.

99% of the time it's used in fan mode (where the element used is within
the fan).

Just went to use it in a different mode where top and bottom elements
used, but not fan, it had been heating up for a couple of minutes then
tripped the RCD in its half of the CU.

Hoped it was a one-off, so reset and tried again, tripped again,
wondered if the internal light was causing it so removed bulb, still
tripped.

Each time after resetting RCD have to prod the timer button to "ack" the
mains failure, then the electronics are on (i.e. clock flashes) if the
main selector knob is "off", it doesn't trip.

If I turn temperature knob to coldest, I can turn the selector knob to
the setting where just the internal light is on, it doesn't trip (a
small cooling fan also runs)

Leaving selector knob in the internal light setting (i.e. no elements or
main fan) then turning up the temperature knob it trips the RCD as soon
as I hear the stat click on.

To me that doesn't scream "earth leaky element" but rather "gunge has
got into stat or across some wiring"

Thoughts?

I'm sure some here will oppose my suggestion.

If this is a 'damp' element then drying it out will provide a temporary
solution. If used frequently then perhaps a longer lasting solution.

With no one else allowed in the vicinity, first turn up the offending
stat. RCD should trip.

Remove the earth to the oven. Flick RCD on. Press the timer button
carefully making not to contact anything metal on the oven.

Hopefully the element will get very hot and after 10 minutes in this
state turn off/trip/test the RCD.

Reconnect the earth.

Well, it a better suggestion than PHucker!

On Monday, 18 December 2017 00:07:56 UTC, Fredxx wrote:
On 17/12/2017 14:08, Andy Burns wrote:
10+ year old Neff oven, just decided to trip RCD, no previous trouble.

99% of the time it's used in fan mode (where the element used is within
the fan).

Just went to use it in a different mode where top and bottom elements
used, but not fan, it had been heating up for a couple of minutes then
tripped the RCD in its half of the CU.

Hoped it was a one-off, so reset and tried again, tripped again,
wondered if the internal light was causing it so removed bulb, still
tripped.

Each time after resetting RCD have to prod the timer button to "ack" the
mains failure, then the electronics are on (i.e. clock flashes) if the
main selector knob is "off", it doesn't trip.

If I turn temperature knob to coldest, I can turn the selector knob to
the setting where just the internal light is on, it doesn't trip (a
small cooling fan also runs)

Leaving selector knob in the internal light setting (i.e. no elements or
main fan) then turning up the temperature knob it trips the RCD as soon
as I hear the stat click on.

To me that doesn't scream "earth leaky element" but rather "gunge has
got into stat or across some wiring"

Thoughts?

I'm sure some here will oppose my suggestion.

If this is a 'damp' element then drying it out will provide a temporary
solution. If used frequently then perhaps a longer lasting solution.

With no one else allowed in the vicinity, first turn up the offending
stat. RCD should trip.

Remove the earth to the oven. Flick RCD on. Press the timer button
carefully making not to contact anything metal on the oven.

Hopefully the element will get very hot and after 10 minutes in this
state turn off/trip/test the RCD.

Reconnect the earth.

Well, it a better suggestion than PHucker!

50% chance of oven being live, lethal to animals and occasionally humans.

Andy Burns wrote:

ARW wrote:

Screams to me knackered element.

I suppose an oven tripping normally would scream "element" to me,
especially using one that hasn't been used for some time.

We occasionally had problems at work getting mineral insulated
metalclad heating elements through insulation test. Running them
for a while could improve matters, but sometimes it got worse. I
have a vague idea that dotH2O became free H2O, but the details
are obscured by the mists of time.

Chris
--
Chris J Dixon Nottingham UK


Plant amazing Acers.

On 18/12/2017 00:07, Fredxx wrote:
On 17/12/2017 14:08, Andy Burns wrote:

If this is a 'damp' element then drying it out will provide a temporary
solution. If used frequently then perhaps a longer lasting solution.


The OP has suggested that the oven works OK in the fan mode so if the
problem is a damp element then just operating the oven in the mode that
still works will dry out the offending element.


--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk

Could be as simple as knackered wiring on the stat. Many moons ago we had a
Belling which had some kind of cracked insulation on a wire.

Nothing lasts forever I guess.
Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"ARW" wrote in message
news
On 17/12/2017 14:08, Andy Burns wrote:
10+ year old Neff oven, just decided to trip RCD, no previous trouble.

99% of the time it's used in fan mode (where the element used is within
the fan).

Just went to use it in a different mode where top and bottom elements
used, but not fan, it had been heating up for a couple of minutes then
tripped the RCD in its half of the CU.

Hoped it was a one-off, so reset and tried again, tripped again, wondered
if the internal light was causing it so removed bulb, still tripped.

Each time after resetting RCD have to prod the timer button to "ack" the
mains failure, then the electronics are on (i.e. clock flashes) if the
main selector knob is "off", it doesn't trip.

If I turn temperature knob to coldest, I can turn the selector knob to
the setting where just the internal light is on, it doesn't trip (a small
cooling fan also runs)

Leaving selector knob in the internal light setting (i.e. no elements or
main fan) then turning up the temperature knob it trips the RCD as soon
as I hear the stat click on.

To me that doesn't scream "earth leaky element" but rather "gunge has got
into stat or across some wiring"

Thoughts?



Screams to me knackered element.

The stat has to be switching something.

--
Adam

alan_m wrote:

The OP has suggested that the oven works OK in the fan mode

No the only mode that works is with just the internal lamp selected, if
any elements are selected but the stat isn't turned right down it trips
(immediately or within a few seconds depending if it's hot/cold)

On 18/12/2017 12:45, Andy Burns wrote:
alan_m wrote:

The OP has suggested that the oven works OK in the fan mode

No the only mode that works is with just the internal lamp selected, if
any elements are selected but the stat isn't turned right down it trips
(immediately or within a few seconds depending if it's hot/cold)

Given the fag of gaining access might it be worth trying a hot air gun
(or failing that a hair-dryer) on the elements?

--
Robin
reply-to address is (intended to be) valid

On 18/12/2017 12:45, Andy Burns wrote:
alan_m wrote:

The OP has suggested that the oven works OK in the fan mode

No the only mode that works is with just the internal lamp selected, if
any elements are selected but the stat isn't turned right down it trips
(immediately or within a few seconds depending if it's hot/cold)

When you think about it, once you pass any current through any element,
you are going to lift the neutral potential just a little bit. If you
then have a short to earth on any element anywhere you may get a trip.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

In article , John
Rumm writes
On 18/12/2017 12:45, Andy Burns wrote:
alan_m wrote:

The OP has suggested that the oven works OK in the fan mode

No the only mode that works is with just the internal lamp selected, if
any elements are selected but the stat isn't turned right down it trips
(immediately or within a few seconds depending if it's hot/cold)

When you think about it, once you pass any current through any element,
you are going to lift the neutral potential just a little bit. If you
then have a short to earth on any element anywhere you may get a trip.


But the OP has said it fails when no element is (or should be) switched
on i.e. internal light only on then temp control turned to just above
zero. I also have 10 year old Neff oven)

--
bert

On 18/12/2017 22:58, bert wrote:
In article , John
Rumm writes
On 18/12/2017 12:45, Andy Burns wrote:
alan_m wrote:

The OP has suggested that the oven works OK in the fan mode

No the only mode that works is with just the internal lamp selected, if
any elements are selected but the stat isn't turned right down it trips
(immediately or within a few seconds depending if it's hot/cold)

When you think about it, once you pass any current through any
element, you are going to lift the neutral potential just a little
bit. If you then have a short to earth on any element anywhere you may
get a trip.


But the OP has said it fails when no element is (or should be) switched
on i.e. internal light only on then temp control turned to just above
zero. I also have 10 year old Neff oven)

If the temp control is anything other than completely off, it will be
passing current through at least one element. Even if that is not the
knackered one, the mechanism I described above could still result in the
trip being caused indirectly from the failed element.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 18/12/2017 03:58, wrote:
On Monday, 18 December 2017 00:07:56 UTC, Fredxx wrote:
On 17/12/2017 14:08, Andy Burns wrote:
10+ year old Neff oven, just decided to trip RCD, no previous trouble.

99% of the time it's used in fan mode (where the element used is within
the fan).

Just went to use it in a different mode where top and bottom elements
used, but not fan, it had been heating up for a couple of minutes then
tripped the RCD in its half of the CU.

Hoped it was a one-off, so reset and tried again, tripped again,
wondered if the internal light was causing it so removed bulb, still
tripped.

Each time after resetting RCD have to prod the timer button to "ack" the
mains failure, then the electronics are on (i.e. clock flashes) if the
main selector knob is "off", it doesn't trip.

If I turn temperature knob to coldest, I can turn the selector knob to
the setting where just the internal light is on, it doesn't trip (a
small cooling fan also runs)

Leaving selector knob in the internal light setting (i.e. no elements or
main fan) then turning up the temperature knob it trips the RCD as soon
as I hear the stat click on.

To me that doesn't scream "earth leaky element" but rather "gunge has
got into stat or across some wiring"

Thoughts?

I'm sure some here will oppose my suggestion.

If this is a 'damp' element then drying it out will provide a temporary
solution. If used frequently then perhaps a longer lasting solution.

With no one else allowed in the vicinity, first turn up the offending
stat. RCD should trip.

Remove the earth to the oven. Flick RCD on. Press the timer button
carefully making not to contact anything metal on the oven.

Hopefully the element will get very hot and after 10 minutes in this
state turn off/trip/test the RCD.

Reconnect the earth.

Well, it a better suggestion than PHucker!

50% chance of oven being live, lethal to animals and occasionally humans.

Hence this should only be done on a temporary basis with no one else
around. Perhaps I should have added, no animals around either.

On 18/12/17 22:58, bert wrote:
In article , John
Rumm writes
On 18/12/2017 12:45, Andy Burns wrote:
alan_m wrote:

The OP has suggested that the oven works OK in the fan mode

No the only mode that works is with just the internal lamp selected, if
any elements are selected but the stat isn't turned right down it trips
(immediately or within a few seconds depending if it's hot/cold)

When you think about it, once you pass any current through any
element, you are going to lift the neutral potential just a little
bit. If you then have a short to earth on any element anywhere you may
get a trip.


But the OP has said it fails when no element is (or should be) switched
on i.e. internal light only on then temp control turned to just above
zero. I also have 10 year old Neff oven)

A netral erath short will trip an RCD whn no equipment is on. It is most
annoying as it will manifest when something unreleted is switched on and
neutral current is 'passing by' your appliance





--
"If you dont read the news paper, you are un-informed. If you read the
news paper, you are mis-informed."

Mark Twain

Beg, borrow or buy an insulation resistance tester.

Cynic wrote:

Beg, borrow or buy an insulation resistance tester.

I've got one, but not (yet) the enthusiasm to drag the oven out, no
turkey to incinerate here, so no rush ...

On 17/12/2017 20:09, Mr Pounder Esquire wrote:
James Wilkinson Sword wrote:
On Sun, 17 Dec 2017 14:08:32 -0000, Andy Burns
wrote:
10+ year old Neff oven, just decided to trip RCD, no previous
trouble. 99% of the time it's used in fan mode (where the element used is
within the fan).

Just went to use it in a different mode where top and bottom elements
used, but not fan, it had been heating up for a couple of minutes
then tripped the RCD in its half of the CU.

Hoped it was a one-off, so reset and tried again, tripped again,
wondered if the internal light was causing it so removed bulb, still
tripped.

Each time after resetting RCD have to prod the timer button to "ack"
the mains failure, then the electronics are on (i.e. clock flashes)
if the main selector knob is "off", it doesn't trip.

If I turn temperature knob to coldest, I can turn the selector knob
to the setting where just the internal light is on, it doesn't trip
(a small cooling fan also runs)

Leaving selector knob in the internal light setting (i.e. no
elements or main fan) then turning up the temperature knob it trips
the RCD as soon as I hear the stat click on.

To me that doesn't scream "earth leaky element" but rather "gunge has
got into stat or across some wiring"

Thoughts?

Remove the RCD. Oh how simple life is with fuses....

That must be the stupidest thing you have ever come out with, Birdbrain.
What a fool you really are.


Actually operating the oven without RCD protection would actually show
if it's a LE or NE fault/

--
Adam

ARW wrote:

Andy Burns wrote:

10+ year old Neff oven, just decided to trip RCD, no previous trouble.

Screams to me knackered element.

Dragged it out today, disconnected all elements, it would run cold
without tripping, high resistance from elements to earth while still
cold, reconnected elements and after warming up on fan setting for a
couple of minutes it tripped, disconnected elements one by one and found
the bottom element is the culprit (the most expensive and for me the
least used).

While warm, the earth resistance from the dodgy element was 60k, after
leaving running for 20 minutes to get decently hot, it got up to about
200k, for now its wires are taped-up and left disconnected.

Andy Burns wrote:

the bottom element is the culprit

Flipped the oven over and got the element out, it looks as clean as a
whistle ... there seem to be only three in stock in the UK (several of
the espares/4neff/partmaster websites are the same thing in disguise)
all want about £50 for it.

There's one available from Holland for £13, but as mine is stamped 240V,
I guess that one might actually be for 220V, so much for harmonised 230V?

On 28/12/2017 17:01, Andy Burns wrote:
Andy Burns wrote:

the bottom element is the culprit

Flipped the oven over and got the element out, it looks as clean as a
whistle ... there seem to be only three in stock in the UK (several of
the espares/4neff/partmaster websites are the same thing in disguise)
all want about £50 for it.

There's one available from Holland for £13, but as mine is stamped 240V,
I guess that one might actually be for 220V, so much for harmonised 230V?

Might...

Given the small 20% possible difference in power, I'd still go for it.

Fredxx wrote:

Andy Burns wrote:

There's one available from Holland for £13

I'd still go for it.

Seems the Dutch website is scraping items from German eBay, and it's
secondhand, so I'll pass ...

Andy Burns wrote:

ARW wrote:

Andy Burns wrote:

10+ year old Neff oven, just decided to trip RCD, no previous trouble.

Screams to me knackered element.

Dragged it out today, disconnected all elements, it would run cold
without tripping, high resistance from elements to earth while still
cold, reconnected elements and after warming up on fan setting for a
couple of minutes it tripped, disconnected elements one by one and found
the bottom element is the culprit (the most expensive and for me the
least used).

While warm, the earth resistance from the dodgy element was 60k, after
leaving running for 20 minutes to get decently hot, it got up to about
200k, for now its wires are taped-up and left disconnected.

Any resistance you can measure with a multimeter is definitely
defective. I would expect it to be gigaohms even at 500V.

--

Roger Hayter

Roger Hayter wrote:

Any resistance you can measure with a multimeter is definitely
defective. I would expect it to be gigaohms even at 500V.

Not sure about gigaohms? I've got no way to distinguish between
100-200M and infinity.

when cold and at 9V (or whatever voltage my multimeter uses) the most
I've seen is 11M, but shortly after a trip the multimeter has variously
read between 60k and 250k, I'd expect it to have to get down to 7k or so
to trip the RCD.

At 500V my insulation tester shows under 100k (impossible to tell how
far under as the next minor graduation on the scale is zero and it
wobbles around in use)

Anyway, with the variations in insulation between cold/warm/hot I'm
convinced it is buggered, even though it looks ok.

Andy Burns wrote:

Roger Hayter wrote:

Any resistance you can measure with a multimeter is definitely
defective. I would expect it to be gigaohms even at 500V.

Not sure about gigaohms? I've got no way to distinguish between
100-200M and infinity.

when cold and at 9V (or whatever voltage my multimeter uses) the most
I've seen is 11M, but shortly after a trip the multimeter has variously
read between 60k and 250k, I'd expect it to have to get down to 7k or so
to trip the RCD.

At 500V my insulation tester shows under 100k (impossible to tell how
far under as the next minor graduation on the scale is zero and it
wobbles around in use)

That's what I was getting at. If the insulation tester shows anything
below maximum resistance with one of those mineral insulated elements
then the element is defective, and will have increasing leakage with
both time and temperature. If one is lucky enough to find this out
before it fails completely one should immediately change it.




Anyway, with the variations in insulation between cold/warm/hot I'm
convinced it is buggered, even though it looks ok.


--

Roger Hayter

On 28/12/2017 16:03, Andy Burns wrote:
ARW wrote:

Andy Burns wrote:

10+ year old Neff oven, just decided to trip RCD, no previous trouble.

Screams to me knackered element.

Dragged it out today, disconnected all elements, it would run cold
without tripping, high resistance from elements to earth while still
cold, reconnected elements and after warming up on fan setting for a
couple of minutes it tripped, disconnected elements one by one and found
the bottom element is the culprit (the most expensive and for me the
least used).


Of course it had to be the most expensive one:-(

It probably has moisture in it.

As Roger said. We both would expect almost infinity at 500V with an
insulation tester.

--


Adam

ARW wrote:

It probably has moisture in it.

I wouldn't mind if I could see that it was corroded or pitted or had
burnt spiders between the terminals and the outer jacket, but it looks
perfect, it's underneath the main oven cavity so no fat/steam would get
anywhere near it. Replacement is on its way.

On 29/12/2017 13:00, Andy Burns wrote:
ARW wrote:

It probably has moisture in it.

I wouldn't mind if I could see that it was corroded or pitted or had
burnt spiders between the terminals and the outer jacket, but it looks
perfect, it's underneath the main oven cavity so no fat/steam would get
anywhere near it.


Replacement is on its way.


So is my new cooker. Bottom oven (fan assisted) element packed in a few
weeks ago. The grill element packed in a few days ago.

Actually both are available at a reasonable price and look easy to
replace. However when fetching in the new settee yesterday (tight space)
the glass on the main oven got smashed.




--
Adam

On 29/12/17 13:00, Andy Burns wrote:
ARW wrote:

It probably has moisture in it.

I wouldn't mind if I could see that it was corroded or pitted or had
burnt spiders between the terminals and the outer jacket, but it looks
perfect, it's underneath the main oven cavity so no fat/steam would get
anywhere near it.Â* Replacement is on its way.

Those elements simply fail internally, often due to thermal cycling
opening up a pinhole and then moisture gets in.

I've replaced more than one. They always look just perfect to me. But a
meter shows otherwise.



--
€œA leader is best When people barely know he exists. Of a good leader,
who talks little,When his work is done, his aim fulfilled,They will say,
€œWe did this ourselves.€�

ۥ Lao Tzu, Tao Te Ching