Calling on professional potters

Hey guys there is some disagreement at my local potters group about how
often kiln elements need replacing. In my own kiln I replaced them after
about 150 firings. The kiln began to take longer and then began to struggle
to reach temp even though none of the elements were broken. I would really
appreciate it if people would post how often they consider it necessary to
replace the kiln elements.
Thanks
Annemarie

Hi Annemarie,

"When the kiln began to take longer and then began to struggle"... is the
ideal time to replace the elements. If you wait until any are broken, that's
too long.

As for how many firings, that's like asking "how long is a piece of string"
.... depends on how high the firings are ... if you were doing glass firings,
your elements could last 1000 firings ... if you were doing all stoneware,
your elements might do 100 firings before the kiln slowed down. Also depends
on how well designed the elements were in the first place.

Best way to tell is to time the firings, and when you aren't happy with the
firing time, change the elements.

Cheers

Dave Coggins



"Xtra News" wrote in message
news
Hey guys there is some disagreement at my local potters group about how
often kiln elements need replacing. In my own kiln I replaced them after
about 150 firings. The kiln began to take longer and then began to
struggle to reach temp even though none of the elements were broken. I
would really appreciate it if people would post how often they consider it
necessary to replace the kiln elements.
Thanks
Annemarie

Dear Annemarie,

Dave Coggins is absolutely right.

To add to what he said; every firing puts a VERY (microscopically) thin
layer of oxide on the element wire, and the core of resistant wire is
reduced by the same amount. In the initial life of the element this
protects it from the harsh conditions in the kiln (so pre-fire new
elements before putting pots in there), but ultimately as Dave said it
gets slower and slower as the core reduces in size.
You could also measure the amperage draw of the kiln when on full as
well as time each firing to get a picture of the element(s) condition.

Steve
Bath
UK


In article , Xtra News Annemarie
@nospam.annemariebutler.com writes
Hey guys there is some disagreement at my local potters group about how
often kiln elements need replacing. In my own kiln I replaced them after
about 150 firings. The kiln began to take longer and then began to struggle
to reach temp even though none of the elements were broken. I would really
appreciate it if people would post how often they consider it necessary to
replace the kiln elements.
Thanks
Annemarie



--
Steve Mills
Bath
UK

"Steve Mills" wrote in message
...
Dear Annemarie,

Dave Coggins is absolutely right.

To add to what he said; every firing puts a VERY (microscopically) thin
layer of oxide on the element wire, and the core of resistant wire is
reduced by the same amount. In the initial life of the element this
protects it from the harsh conditions in the kiln (so pre-fire new
elements before putting pots in there), but ultimately as Dave said it
gets slower and slower as the core reduces in size.
You could also measure the amperage draw of the kiln when on full as
well as time each firing to get a picture of the element(s) condition.

Steve
Bath
UK



Thanks guys, this is exactly the sort of stuff I need to convince the
skeptics that the elements need changing. The club kiln has got slower and
the firing uneven when it used to be very even from top to bottom and
because none of the elements is broken and they will still take a current it
is thought that new elements are not needed. I did check and it had done
well over 150 firings bisque and cone 6 mostly, but some earthenware and
stoneware as well. However just looking at the elements (very brittle
looking and many falling over) and looking at how the kiln is firing has
convinced me that new elements are essential before they fail during a
firing. More advise would be great, the more I can take the more convincing
it will be )

Hi Annemarie,

When I was repairing kilns, I had many customers who persisted in flogging
their old elements to death, or only replacing a broken element rather than
the whole lot at the same time, and they continued grumbling about how bad
the firings were and how many pieces they lost - it's hard to convince some
people.

The best way to get hard evidence that the elements need replacing is to get
an electrician to measure the current drawn by the kiln using a proper
current meter (clamp meter) while the elements are HOT - preferably near
maximum temp. - as elements draw less power when hot. Compare the reading
with the rated current on the kiln plate.

Any kiln which draws a current 10% or greater below the original value will
generally fail to reach top temp, or take so long getting there that the
ware will be overfired.

Also, if the element coils are falling over and touching, it's only a matter
of time before one of the coils shorts out to another, and the element will
burn out.

Another point you could mention is that the kiln is using so much more power
because of the slow firings, also many pieces are not firing properly due to
the unevenness of the kiln and have to be refired - this is wasteful of
energy and money, and makes the kiln uneconomical to operate.

Having said that, the150 mixed firings you describe doesn't really seem to
be a very good total - maybe the original element design was a bit light for
the job and it might be worth looking at getting a heavier duty design if
possible, particularly as group kilns always seem to have a hard life. A
heavier duty design could dramatically increase the number of firings for a
little extra money.

There is some information which may help on my website -
www.users.bigpond.com/dcoggins

Good luck!!

Dave Coggins

"

Thanks guys, this is exactly the sort of stuff I need to convince the
skeptics that the elements need changing. The club kiln has got slower
and the firing uneven when it used to be very even from top to bottom and
because none of the elements is broken and they will still take a current
it is thought that new elements are not needed. I did check and it had
done well over 150 firings bisque and cone 6 mostly, but some earthenware
and stoneware as well. However just looking at the elements (very brittle
looking and many falling over) and looking at how the kiln is firing has
convinced me that new elements are essential before they fail during a
firing. More advise would be great, the more I can take the more
convincing it will be )

Well, there ya go, let that be a lesson to all those nay-sayers! Of
course for most folks the bottom line is still the bottom line which
brings me to ask, what's it cost to fix? Can anybody make these repairs
or should you call in a professional? If you have three ducks and the
recipe calls for seven, oh no, wait, that's a whole other subject. Umm,
where was I? Oh yeah... Whenever I work with electricity, if I see lots
of sparks or my hair stands on end all by itself, I figure its time to
call in a professional. ...Although the hair thing does look kinda
cool. 8-)

~Kroozr

"the ''Kroozr''" wrote in message
...
Well, there ya go, let that be a lesson to all those nay-sayers! Of
course for most folks the bottom line is still the bottom line which
brings me to ask, what's it cost to fix? Can anybody make these repairs
or should you call in a professional? If you have three ducks and the
recipe calls for seven, oh no, wait, that's a whole other subject. Umm,
where was I? Oh yeah... Whenever I work with electricity, if I see lots
of sparks or my hair stands on end all by itself, I figure its time to
call in a professional. ...Although the hair thing does look kinda
cool. 8-)

~Kroozr

Cost approx NZ$400 installed by professional electrician. Bottom line,
yeah, there has been a lot of spending on glaze materials and shelves when
the kiln needed fixing......

NZ$400 is expensive and I can see how some would balk at spending that
kind of money. 150 firings really isn't a lot of firings. I have an
electric kiln and I can see its going to be costly just to keep it in
proper running order. But if its the nature of the beast and rewiring
gives you a better firing as well as safer use of the equipment, then
its a no-brainer. Safety is a big concern, the idea of wires shorting
out, that can't ever have a good outcome.

~Kroozr

"the ''Kroozr''" wrote in message
...
NZ$400 is expensive and I can see how some would balk at spending that
kind of money. 150 firings really isn't a lot of firings. I have an
electric kiln and I can see its going to be costly just to keep it in
proper running order. But if its the nature of the beast and rewiring
gives you a better firing as well as safer use of the equipment, then
its a no-brainer. Safety is a big concern, the idea of wires shorting
out, that can't ever have a good outcome.

~Kroozr


When you break it down it is only $2.60 per firing. There is of course a
kiln fee which covers electricity, and glaze, it is also supposed to cover
kiln maintenance. When you think about it, thats not really terribly much
for a 6cf kiln with a club firing. However I was slightly missleading. A
few months ago I counted how many firings this kiln had done and it was over
150 then. I will count again )

I think that 150 sounds typical. It would I presume be a mixture of
biscuit and glaze firings.

As you say the firings take longer and longer with more usage and at
some point the firings may become so long that it becomes economic to
fit a new set of elements. The higher the temperature of your firings
the sooner this point is reached.

Another factor is the actual voltage of your supply. Any power supplier
is allowed quite a large range within which he must stay. The nominal
may be 240 volts say but the lower limit may be 210 volts. When I
re-order elements I specify that they are for the lower limit and they
are cut to length accordingly. This in effect gives them a longer life
before the length of a firing becomes uneconomic.

David



In message , Xtra News
writes
Hey guys there is some disagreement at my local potters group about how
often kiln elements need replacing. In my own kiln I replaced them after
about 150 firings. The kiln began to take longer and then began to struggle
to reach temp even though none of the elements were broken. I would really
appreciate it if people would post how often they consider it necessary to
replace the kiln elements.
Thanks
Annemarie



--
David Hewitt