Bob Masta on tue 13 jul 04
Industrial ovens typically use silicon carbide rods as
heating elements. These are very low resistance and
rather finicky. You'd typically need a high-current low-voltage
transformer weighing about 100 pounds or so to drive
a pottery kiln, or better yet a special electronic controller
that can give the same average current. You don't want
to use "infinity" type (on-off) temperature regulation, since
switching these rods off and on like that shortens their
life. Instead, you need a proportional regulator like a
giant lamp dimmer, or (in the olden days) a multi-tap
transfomer that you can adjust manually.
On top of that, the rods can't be too close to a reflective
surface like the kilns walls; they typically must be a
couple of diameters away. So in a smallish pottery kiln
(compared to an industrial unit) you have these rods
in the same area where you stack your wares. And
of course, you don't want drips of glaze or stuff on them.
I don't know about longevity, but I suspect that industiral
kilns which tend to use long, steady temperatures (some
run all the time, with the wares passing through on conveyor)
may find these more economical. The prices seem high,
but not unreasonably so. I just bought a couple of rods with
13" hot zones for just over $50 each. Each rod is custom built,
and the main expense is for the setup... longer rods aren't much more.
All in all, not practical for small pottery kilns. (So why am I
building a kiln based on these things? Long story, in which
obstinance and lack of common sense and good judgement
may play a starring role....)
Bob Masta
potsATdaqartaDOTcom
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