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the various and sundry creations of sylvus tarn
Kiln & Controller
excerpted from a letter to a friend...

Speaking of glass, the kiln stopped working, right when I switched it to anneal. It happened like this:

One of the strands of the electrical cord hooking to the elements—which itself is basically a thick, twisted pair wrapped into a 1/2” or so diameter coil (and threaded thru quartz tubing, to prevent electrocution when sticking metal mandrels in there;)—burnt through. I mean, completely thru. It was fried. At first I thought my kiln was broken because the controller had died again: one of the poles of its relay switch had fried out, but since it's a 3pole relay, rob switched it to another pole several years ago. Well, when he took it apart, the second pole looked equally cooked, so he switched to the last pole.

Since the temp didn't seem to be rising very much after he ‘fixed’ the controller I tried a very simple experiment, and eliminated a variable, the controller: plugged the kiln directly into the wall, eliminating the controller Science to the rescue! (Normally you would never do this: plugging a kiln directly into the wall without a temp sensor isn't the greatest idea because there's nothing to keep the electricity from heating and heating and heating the element till they fry out, or mebbe set something on fire, and without a temp sensor, I would have only the crudest of ways of knowing how hot the kiln was—either by feeling the bricks or opening it up and looking at the elements. But it usually takes it 10 minutes to get to 900 or so, so I set a timer for 3, and then unplugged it.) Plugged it back into the controller, and it still read only 109 degrees. (Residual heat from earlier that day.) At that point I looked more carefully at the junction box mounted on the side, which as you may recall is that metal mesh full of holes (for heat dissipation), and I could kinda see that one of the wires looked burnt thru.

Last time Craig Milliron coached [the wizard] through an error2 reset after he switched poles, but neither the technical guy nor [the wizard] felt it was necessary (so far seems fine), so we skipped that step this time. —What happened was, after [the wizard] switched poles on the relay of my controller I called Arrow Springs to confirm everything was all right. Well, the guy was out to lunch, and between then and the time he called back, I discovered the fried wire. [The wizard] was not pleased to hear the fellow's advice, which was basically:

1. strip wire back 5” (way too much, [the wizard] said. But I think he should've stripped back to clean copper, at least.)

2. replace the allen wrench nut holding the connection together, because they tend to corrode and become cross-threaded. It has to be stainless steel, as opposed to ordinary garden variety which is not conductive enough, and since mine wasn't very corroded—it didn't strip at all when [the wizard] undid it—we just reused it. This is probably because I garage my kiln at 890–900 most of the time, have short, 1/2 hour soaks (those thin-walled hollow beads!) which even so only go up to 980. If I were doing long big-boro bead schedules, or worse, fusing, let alone raking, all the time, that connection would no doubt have been in a lot sorrier state. Another side bennie is that the elements will probably last the rest of my life, unless they crack from brittleness. —Except, I keep having these fusing fantasies...

3. Buy un-insulated circle connectors. Those are hard to find. [The wizard] just got the insulated kind and cut the plastic sheath off. I'm not certain where he found the crimping tool—it's somewhat unusual—but he had something that worked.

So my kiln was back up and running the same day, and I was once again delighted by Arrow Springs’ customer service, and [the wizard], of course is Teh Awesome. (Though honestly, if it happened again, even I could fix that. It really is a quite simple wiring problem.) And another piece of good news is that when that relay finally craps out, AS carries a suitable replacement part. I had visions of having to pitch a $500 controller for lack of a $20 part—the company that manufactures it is out of business. Evidently, however, they were just the subcontractor for AS, so as long as they're in business I'm good to go...in fact, I gather this relay is actually a commodity part, and likely to remain one for awhile.

And I even managed to save the leopard head that I spent an hour and a half on when the kiln died. Which, having had 3 crap out from bead release problems was something of a relief. I'm still thinking about buttons, especially ones with tigers and other cat heads on ’em. Sculptural is a very cold technique, and it's quite possible that once I get decent at it, the temperature problems with buttons will seem trivial (not to mention the broken bead release problems) in comparison.

Note to sylvus: the wizard's phone has a pic of the relay on it. filed originally created 17jan10. (from letter written 14jan10.)