Robert Schapansky on tue 19 nov 96
(I believe I too was off the list and am re-posting this message)
Hi all;
Murphys' Law dictates that if something will go wrong, it will do so
at the worst possible time.
My second hand Duncan electric kiln has until now had a very
consistant firing schedule. In that a bisque would usually shut off at a
certain time consistant with all other bisque firings and the same goes for
a glaze kiln; with only a little variation as a result of different load sizes.
However, over the last four firings this has changed entirely; in
fact, this morning my bisque kiln shut off 5 hours earlier than it has done
before. It had a very slow firing (in that I had it going on low over night)
after turning it up to med. it was on for only an hour longer before it shut
off. The witness cones (decided I had better start using them so that I
would have at least some small idea of what was going on in there) varied
from top to bottom peep hole but indicated that it has reached 06.
My question is; what could be causing such a marked difference in
firing time? Its as though suddenly the kiln is much hotter at a lower setting.
Since I have several orders on which I have had to delay delivery
dates due to firing problems...underfiring and refiring problems (pits and
pebbled surfaces which leads me to believe it was underfired).....I really
need any advice or insight into this problem as soon as possible.
TIA
Elizabeth Schapansky
David Woodin clayart Digest on wed 20 nov 96
If the switches are the infinite type (pulses on and off) it could be that
one of the switches is stuck in the made position and you will then get full
heat from this switch no matter what it is set for. Sometimes you can get a
switch of this type from an appliance parts store. It is used on an electric
stove.
Jean Silverman on fri 22 nov 96
Elizabeth,
I had what sounds like the exact same thing happen with my electric kiln
last year; suddeny it began getting to cone 9 in 6 hrs. instead of 8 or 9.
Also, the elements would be glowing while the switches were still
(theoretically) at a low or medium setting. I didn't know what was
happening but kept firing anyway, maybe 10 or 12 more times. Then for some
reason I decided to check the various connections in case they needed cleaning.
I pulled the plug on the line that carries power from the center to the
upper ring and got the (figurative) shock of my life--the plug itself had
melted almost into a puddle; even the prongs were eaten away! When my
electrician came over he said this was caused by a defective part--I forget
its name--essential to the power transfer to the other ring. He replaced the
part and the defunct power line and cord and the kiln went back to its
normal firing behavior. Luckily I'd found the damage just before major
meltdown, but I shudder to think...!
So the point of this is: this is a problem for a pro. Run, don't walk, to
your phone and get your electrician to test all the parts of your kiln's
wiring; something is definitely wrong somewhere!
Best of luck, Jean
------------------------------------------------------------
Jean Silverman
jeansil@nh.ultranet.com
41 Neal Mill Road
Newmarket NH 03857 603-659-2632 fax: 603-659-4728
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