A mate has asked me about his kiln (for clay pots and things), - obviously, I
didn't know, so . . .

It gets to about 1000C, but struggles to reach 1200C. From new it did this
quite readily, he says. The slightly odd thing is that it still has the
same/consistent energy draw, with no apparent losses such as heat leaks or
noises of any kind. So I'm not sure where the energy is going.

Any ideas?

--
Cheers, Rob

On 01/05/2020 14:46, RJH wrote:
A mate has asked me about his kiln (for clay pots and things), - obviously, I
didn't know, so . . .

It gets to about 1000C, but struggles to reach 1200C. From new it did this
quite readily, he says. The slightly odd thing is that it still has the
same/consistent energy draw, with no apparent losses such as heat leaks or
noises of any kind. So I'm not sure where the energy is going.

Any ideas?


mains down to 187v ? :-)

On 01/05/2020 14:46, RJH wrote:
A mate has asked me about his kiln (for clay pots and things), - obviously, I
didn't know, so . . .

It gets to about 1000C, but struggles to reach 1200C. From new it did this
quite readily, he says. The slightly odd thing is that it still has the
same/consistent energy draw, with no apparent losses such as heat leaks or
noises of any kind. So I'm not sure where the energy is going.

Any ideas?

What Chris Hogg said...
Unless there's something really weird going on, slow heating of kilns
(my experience is in fused-glass rather than ceramics, and we 'only' go
up to 800c or so) suggests that either the infinite controller on his
kiln is faulty, or he (more likely) has at least one set of elements
open-circuit.

Should be possible to confirm this by taking a quick look as the kiln
heats up - the elements that aren't glowing are open-circuit - either at
the wired connections or the element itself. A multimeter check across
the individual elements will confirm this.

Typically the kiln has enough power input to heat up, but not as fast or
as hot as expected..
How's he measuring the input power?

"RJH" wrote in message
...
A mate has asked me about his kiln (for clay pots and things), -
obviously, I
didn't know, so . . .

It gets to about 1000C, but struggles to reach 1200C. From new it did this
quite readily, he says. The slightly odd thing is that it still has the
same/consistent energy draw, with no apparent losses such as heat leaks or
noises of any kind. So I'm not sure where the energy is going.

Any ideas?

If it has a thermostat, likely that is the problem.

On Sat, 2 May 2020 04:50:56 +1000, cantankerous trolling geezer Rodent
Speed, the auto-contradicting senile sociopath, blabbered, again:

FLUSH the trolling senile asshole's latest troll**** unread

--
dennis@home to retarded senile Rot:
"sod off rod you don't have a clue about anything."
Message-ID:

But why, when its been working?
My only involvement with electric Kilns was at school and often it seemed
the lagging needed to be replaced, but I'd have thought that would be pretty
noticeable!

Thermostat not working properly maybe? IE if it can be turned up would it
get to the desired temp faster?
Brian

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

Blind user, so no pictures please
Note this Signature is meaningless.!
"Andrew" wrote in message
...
On 01/05/2020 14:46, RJH wrote:
A mate has asked me about his kiln (for clay pots and things), -
obviously, I
didn't know, so . . .

It gets to about 1000C, but struggles to reach 1200C. From new it did
this
quite readily, he says. The slightly odd thing is that it still has the
same/consistent energy draw, with no apparent losses such as heat leaks
or
noises of any kind. So I'm not sure where the energy is going.

Any ideas?


mains down to 187v ? :-)

On 01/05/2020 21:39, Chris Hogg wrote:
On Fri, 1 May 2020 20:51:58 +0100, "Brian Gaff \(Sofa\)"
wrote:

But why, when its been working?
My only involvement with electric Kilns was at school and often it seemed
the lagging needed to be replaced, but I'd have thought that would be pretty
noticeable!

Thermostat not working properly maybe? IE if it can be turned up would it
get to the desired temp faster?

By the time they get above 1000°C, most small pottery kilns are
running flat out anyway. The t/stat only serves to cut them off when
they get to peak temperature, or a little before that to stop
overshoot if they are 'three term' PID types.
https://en.wikipedia.org/wiki/PID_controller


A faulty thermostat could cut out power sooner when the kiln is at a
lower temperature. If the OP is seeing the exactly the same power taken
whilst the kiln is heating up then the elements may be OK but just
turned off too soon, at lower temperature, by a faulty thermostat or a
self resetting over temperature cut-out.

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

On 01/05/2020 21:39, Chris Hogg wrote:
On Fri, 1 May 2020 20:51:58 +0100, "Brian Gaff \(Sofa\)"
wrote:

But why, when its been working?
My only involvement with electric Kilns was at school and often it seemed
the lagging needed to be replaced, but I'd have thought that would be pretty
noticeable!

Thermostat not working properly maybe? IE if it can be turned up would it
get to the desired temp faster?

By the time they get above 1000°C, most small pottery kilns are
running flat out anyway. The t/stat only serves to cut them off when
they get to peak temperature, or a little before that to stop
overshoot if they are 'three term' PID types.
https://en.wikipedia.org/wiki/PID_controller

Yes - it's not a thermostat in the sense of 'keep the water in my hot
tank nice & warm' - it's more of a 'we're at temperature, cut off now'
device (traditionally operated by a ceramic 'cone' deforming at a preset
temperature and cutting the power).

More modern kit might have an electronic controller - so there's some
control over the rate of heating..

Glass-work is a bit more complicated - and tends to involve multiple
segments with ramp / target temperature / hold time - both on the
heating-up and on the annealing/cooling-down stages...

On 01/05/2020 14:46, RJH wrote:
A mate has asked me about his kiln (for clay pots and things), - obviously, I
didn't know, so . . .

It gets to about 1000C, but struggles to reach 1200C. From new it did this
quite readily, he says. The slightly odd thing is that it still has the
same/consistent energy draw, with no apparent losses such as heat leaks or
noises of any kind. So I'm not sure where the energy is going.

Any ideas?


I have a small kiln and to improve that situation I made wrap-around
"pillows" of glass-fibre roof insulation inside "pillow-cases" of the
woven glass fibre mat as used in car-body repair.
Don't rely on thermostat readings, get a range of proving cones to
confirm/calibrate any meter readings

My use of a kiln, to test out versions of things called mathematical tiles.
http://diverse.4mg.com/math_tiles.htm


--
Monthly public talks on science topics, Hampshire , England
http://diverse.4mg.com/scicaf.htm

N_Cook wrote:

My use of a kiln, to test out versions of things called mathematical tiles.
http://diverse.4mg.com/math_tiles.htm

Presume you're aware by now who supplies McDonalds?

https://www.eurobrick.co.uk/project/mcdonalds

On 02/05/2020 10:15, Chris Hogg wrote:
On Sat, 02 May 2020 08:51:55 +0100, N_Cook wrote:

On 01/05/2020 14:46, RJH wrote:
A mate has asked me about his kiln (for clay pots and things), - obviously, I
didn't know, so . . .

It gets to about 1000C, but struggles to reach 1200C. From new it did this
quite readily, he says. The slightly odd thing is that it still has the
same/consistent energy draw, with no apparent losses such as heat leaks or
noises of any kind. So I'm not sure where the energy is going.

Any ideas?


I have a small kiln and to improve that situation I made wrap-around
"pillows" of glass-fibre roof insulation inside "pillow-cases" of the
woven glass fibre mat as used in car-body repair.
Don't rely on thermostat readings, get a range of proving cones to
confirm/calibrate any meter readings

My use of a kiln, to test out versions of things called mathematical tiles.
http://diverse.4mg.com/math_tiles.htm

Whoa! Hold on a minute! I certainly wouldn't put any old glass fibre,
whether loft insulation or mat, into a pottery kiln without being very
sure it would stand the temperatures I was using without melting. What
temperature are you firing to? Your mathematical tiles look like thin
bricks, so I imagine you're firing them to temperatures probably
around 1000°C, rather than the 1200°C the OP's friend goes to.

Fiberglass varies considerably in composition, depending on method of
manufacture (or it did in the days when I was more closely involved),
for example whether air-blown (insulation type) or from spinnerets
(fibre mat). The OP's mate would have to test small samples very
thoroughly before going down that route. And extra internal insulation
would take up space in the kiln, which the OP's friend may not want to
sacrifice.

If the OP's friend wants to put a pad of insulation under his kiln
lid, then I would recommend he use a ceramic fibre specially intended
for kiln use, such as Kaowool or alumina fibre.
https://www.amazon.com/kaowool/s?k=kaowool and
https://almathcrucibles.com/product-...fibre-blanket/

Nor would I use cones to calibrate a thermocouple. Use them as a very
rough guide, perhaps, or as a means of achieving a reproducible firing
schedule, but certainly not as a thermocouple calibration.

Ceramic cones 'go down' at different temperatures, depending on their
composition and the rate of temperature rise. Potters refer to them as
measuring the rather imprecise term 'heat work'. Cones, being made of
similar materials to pottery clay and glazes, behave similarly to the
pots and glazes being fired, so some potters prefer them to
thermocouple measurements. A cone fired up slowly will 'go down' at a
lower temperature than the same cone fired fast. For example, cone 7
will go down at ~1200°C when fired up at 15°C/hr, ~1240°C when fired
up at 60°C/hr, and ~1260°C when fired up at 150°C/hr, a range of
roughly 60°C between slow and fast firing. Not a good method for
calibrating a thermocouple.
http://www.overglazes.com/PDF/Orton-Cone-Chart-C.pdf (I don't believe
the precision to which the cone temperatures are quoted here! Cones
are just not that precise devices).



Pillows wrapped around the outside of the kiln. Cones otherwise called
witness cones as you can lay them in the area of the clay being fired,
not in the wall of the kiln which can be locally hotter or colder than
the centre.

--
Monthly public talks on science topics, Hampshire , England
http://diverse.4mg.com/scicaf.htm

On 2 May 2020 at 10:30:24 BST, "Andy Burns" wrote:

N_Cook wrote:

My use of a kiln, to test out versions of things called mathematical tiles.
http://diverse.4mg.com/math_tiles.htm

Well well, never knew that. Thanks!


Presume you're aware by now who supplies McDonalds?

https://www.eurobrick.co.uk/project/mcdonalds

Or that.

--
Cheers, Rob

On 02/05/2020 11:26, RJH wrote:

Presume you're aware by now who supplies McDonalds?

https://www.eurobrick.co.uk/project/mcdonalds

I wonder what the fire-proof/propogation-supression of the insulation behind
https://www.eurobrick.co.uk/x-clad
is like, post-Grrnfel.
Something similar is used on local student high rise accommodation
blocks, otherwise looks like brick cladding , until delivery lorries
back into it, exposing the foam.

--
Monthly public talks on science topics, Hampshire , England
http://diverse.4mg.com/scicaf.htm

On 01/05/2020 14:46, RJH wrote:
A mate has asked me about his kiln (for clay pots and things), - obviously, I
didn't know, so . . .

It gets to about 1000C, but struggles to reach 1200C. From new it did this
quite readily, he says. The slightly odd thing is that it still has the
same/consistent energy draw, with no apparent losses such as heat leaks or
noises of any kind. So I'm not sure where the energy is going.

Any ideas?



If its getting to 1000C then elemenst must be deemed OK, especially if
same power draw.
Which leaves 2 options ..... either heat is escaping quicker (ladding or
door fit)
Or thermostat is not behaving itself (more likely.)

On 21/06/2020 22:14, rick wrote:
On 01/05/2020 14:46, RJH wrote:
A mate has asked me about his kiln (for clay pots and things), -
obviously, I
didn't know, so . . .

It gets to about 1000C, but struggles to reach 1200C. From new it did
this
quite readily, he says. The slightly odd thing is that it still has the
same/consistent energy draw, with no apparent losses such as heat
leaks or
noises of any kind. So I'm not sure where the energy is going.

Any ideas?



If its getting to 1000CÂ* then elemenst must be deemed OK, especially if
same power draw.
Which leaves 2 options ..... either heat is escaping quicker (ladding or
door fit)
Or thermostat is not behaving itself (more likely.)



I don't think we ever did get any feedback from the original poster back
in May - but a common failure mode on ceramic and glass kilns which have
multiple elements is that one (or more) of the elements fails.

The effect is as RJH described - the kiln can heat up initially as
normal (though a little more slowly) - but at higher temperatures the
reduced heating effect (from having only some of the elements working)
prevents the kiln from reaching the desired temperature.
I'd imagine this is because the rate of heat loss from the kiln
increases as it's internal temperature increases, until it reaches a
kind of 'stalemate' situation.

Same effect can be seen on glass and ceramic kilns which have multiple
elements, each driven by a separate relay. If one of the relays fails,
the kiln will fail to reach the top temperature.

On Friday, 1 May 2020 14:46:06 UTC+1, RJH wrote:
A mate has asked me about his kiln (for clay pots and things), - obviously, I
didn't know, so . . .

It gets to about 1000C, but struggles to reach 1200C. From new it did this
quite readily, he says. The slightly odd thing is that it still has the
same/consistent energy draw, with no apparent losses such as heat leaks or
noises of any kind. So I'm not sure where the energy is going.

Any ideas?

There's probably more than one heating element.
So, one might be open circuit.
It will have to opened up and a continuity meter used to check they are all OK.

Adrian Brentnall wrote:

RJH wrote:

A mate has asked me about his kiln
it still has the same/consistent energy draw

a common failure mode on ceramic and glass kilns which have
multiple elements is that one (or more) of the elements fails.

But you'd expect to see a lower power consumption?

On 22 Jun 2020 at 08:49:04 BST, "Adrian Brentnall"
wrote:

On 21/06/2020 22:14, rick wrote:
On 01/05/2020 14:46, RJH wrote:
A mate has asked me about his kiln (for clay pots and things), -
obviously, I
didn't know, so . . .

It gets to about 1000C, but struggles to reach 1200C. From new it did
this
quite readily, he says. The slightly odd thing is that it still has the
same/consistent energy draw, with no apparent losses such as heat
leaks or
noises of any kind. So I'm not sure where the energy is going.

Any ideas?



If its getting to 1000CÂ* then elemenst must be deemed OK, especially if
same power draw.
Which leaves 2 options ..... either heat is escaping quicker (ladding or
door fit)
Or thermostat is not behaving itself (more likely.)



I don't think we ever did get any feedback from the original poster back
in May - but a common failure mode on ceramic and glass kilns which have
multiple elements is that one (or more) of the elements fails.

Yes, sorry. He's a bit tricky to pin down as I don't think he described what
was happening accurately, and wanted to be told what he wanted to hear. Which
was that the elements had gone - he's now replaced them and I think now is all
well.

I've just sent him an email asking to set out what the symptoms/cure was - but
I don't expect a straight answer. Whatever, i'll pass it on - thanks for all
the feedback.


The effect is as RJH described - the kiln can heat up initially as
normal (though a little more slowly) - but at higher temperatures the
reduced heating effect (from having only some of the elements working)
prevents the kiln from reaching the desired temperature.
I'd imagine this is because the rate of heat loss from the kiln
increases as it's internal temperature increases, until it reaches a
kind of 'stalemate' situation.

Same effect can be seen on glass and ceramic kilns which have multiple
elements, each driven by a separate relay. If one of the relays fails,
the kiln will fail to reach the top temperature.


--
Cheers, Rob

On 22/06/2020 08:49, Adrian Brentnall wrote:
On 21/06/2020 22:14, rick wrote:
On 01/05/2020 14:46, RJH wrote:
A mate has asked me about his kiln (for clay pots and things), -
obviously, I
didn't know, so . . .

It gets to about 1000C, but struggles to reach 1200C. From new it did
this
quite readily, he says. The slightly odd thing is that it still has the
same/consistent energy draw, with no apparent losses such as heat
leaks or
noises of any kind. So I'm not sure where the energy is going.

Any ideas?



If its getting to 1000CÂ* then elemenst must be deemed OK, especially
if same power draw.
Which leaves 2 options ..... either heat is escaping quicker (ladding
or door fit)
Or thermostat is not behaving itself (more likely.)



I don't think we ever did get any feedback from the original poster back
in May - but a common failure mode on ceramic and glass kilns which have
multiple elements is that one (or more) of the elements fails.

The effect is as RJH described - the kiln can heat up initially as
normal (though a little more slowly) - but at higher temperatures the
reduced heating effect (from having only some of the elements working)
prevents the kiln from reaching the desired temperature.
I'd imagine this is because the rate of heat loss from the kiln
increases as it's internal temperature increases, until it reaches a
kind of 'stalemate' situation.

Same effect can be seen on glass and ceramic kilns which have multiple
elements, each driven by a separate relay. If one of the relays fails,
the kiln will fail to reach the top temperature.



Possibly ..... but going on the OP comment that "same/consistent energy
draw", which it wouldn't be if an element had failed.
I didn't realise OP was in May .... guess he is not going to respond
further.

On 22 Jun 2020 at 10:11:00 BST, "RJH" wrote:

On 22 Jun 2020 at 08:49:04 BST, "Adrian Brentnall"

wrote:

On 21/06/2020 22:14, rick wrote:
On 01/05/2020 14:46, RJH wrote:
A mate has asked me about his kiln (for clay pots and things), -
obviously, I
didn't know, so . . .

It gets to about 1000C, but struggles to reach 1200C. From new it did
this
quite readily, he says. The slightly odd thing is that it still has the
same/consistent energy draw, with no apparent losses such as heat
leaks or
noises of any kind. So I'm not sure where the energy is going.

Any ideas?



If its getting to 1000CÂ* then elemenst must be deemed OK, especially if
same power draw.
Which leaves 2 options ..... either heat is escaping quicker (ladding or
door fit)
Or thermostat is not behaving itself (more likely.)



I don't think we ever did get any feedback from the original poster back
in May - but a common failure mode on ceramic and glass kilns which have
multiple elements is that one (or more) of the elements fails.

Yes, sorry. He's a bit tricky to pin down as I don't think he described what
was happening accurately, and wanted to be told what he wanted to hear. Which
was that the elements had gone - he's now replaced them and I think now is
all
well.

I've just sent him an email asking to set out what the symptoms/cure was -
but
I don't expect a straight answer. Whatever, i'll pass it on - thanks for all
the feedback.


The effect is as RJH described - the kiln can heat up initially as
normal (though a little more slowly) - but at higher temperatures the
reduced heating effect (from having only some of the elements working)
prevents the kiln from reaching the desired temperature.
I'd imagine this is because the rate of heat loss from the kiln
increases as it's internal temperature increases, until it reaches a
kind of 'stalemate' situation.

Same effect can be seen on glass and ceramic kilns which have multiple
elements, each driven by a separate relay. If one of the relays fails,
the kiln will fail to reach the top temperature.

His update, when I asked him what the fault was, and to confirm details of
energy draw:
--
Element changed, all working well. The question was whether there was any
damage likely to the kiln workings from continuing to use an old element that
wasnt getting up to temp within the programmed parameters. The actual
limitation was the glazes that werent performing too well having been soaked
for a couple of hours at 1200.
--

He didn't respond to the energy bit - I wouldn't expect him to. He's also
recast the original query, but hey.

--
Cheers, Rob

On 22 Jun 2020 at 20:44:33 BST, "Chris Hogg" wrote:

On Mon, 22 Jun 2020 18:05:53 +0000 (UTC), RJH
wrote:


His update, when I asked him what the fault was, and to confirm details of
energy draw:
--
Element changed, all working well. The question was whether there was any
damage likely to the kiln workings from continuing to use an old element that
wasnÂ’t getting up to temp within the programmed parameters. The actual
limitation was the glazes that werenÂ’t performing too well having been soaked
for a couple of hours at 1200Â’.
--

He didn't respond to the energy bit - I wouldn't expect him to. He's also
recast the original query, but hey.

The kiln won't have been damaged. Most of these small studio pottery
kilns can happily take temperatures well in excess of 1200°C with no
problems, so soaking at that temperature will have done no harm. I
used to run a little kiln regularly up to 1280°C, and I imagine it was
of similar construction. None of the control gear would be affected
either.

Ta, I'll pass that on . . .

--
Cheers, Rob