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Electric burnout kiln kicked the bucket


#1

Hello everybody,

The thermo-controller on my electric burnout kiln kicked the bucket.
Its made by A.L. Engelhardt and I couldn’t find any info on it any
where. It has a pyrometer that presumably moves a puchrod up and
down, which in turn operates a pressure switch to turn the kiln on or
off based on what temp you set using the indexing screw at the top.
Its all mechincal and a finicky little thing. used to work great
until recently. Now, the movement of the pyrometer (thermo
expansion/contraction maybe?) either doesn’t work itself, or the
mechanics involved in transferring that subtle motion to the pressure
switch assembly have too much friction, degraded, fallen out-o-spec,
etc. so that thetemp of the kiln no longer drives the operation of
the switch. I disassembled it only very slightly, but putting it back
together, it doesn’t seem to behave as before. I’m looking for any
help of any kind! Also, any ideas on how to test it and/or calibrate
(temp) would be welcome. In fact, any ideas on a cheap replacement
are welcome too!

Here are some pictures


Thanks so much!
Russ


#2

I have a homemade external controller that can be used on any kiln or
oven to hold an approximate temperature. These are called a
"continuous switch" and are the control that are on many ovens that
don’t have a digital controller. You can get a replacement at any
electrical supply store. Just ask for a replacement “oven
controller.” It looks sort of like a rheostat. They should cost $15
to $20. The oven controller works on the basis of a bi-metalic strip
that turns the oven on and off repetitively at different rates
depending on the setting. The longer the switch stays on the hotter
the oven gets. They are not calibrated so one has to experimentally
find the proper setting. I have mine marked at a setting that will
hold 1350 F for burnout. I don’t use a digital controller for
burnout because I just turn the oven on and it eventually rises to
1350 and holds that temperature until I am ready to change to casting
temperature. Works fine.

Fred