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I am getting really tired...
Mar. 27th, 2016 10:36 pm…of repairing this kiln!
Second firing since the last repairs. First one went perfectly, this one, not. In a normal firing, after time spent warming up the kiln--lid open, lid half-closed, switches on Low or Medium--I'll eventually close the lid, set all the switches to High, and in around six or seven hours, the kiln will reach temperature, the cone will bend, and the kiln sitter shut down.
Friday night around 10:30 pm, I went to check that the kiln had shut down. Nope. Glowing orange hot, though, so I thought we were close. 11:30, still no joy. Bottom peep hole isn't glowing as brightly as the top, though. I wiggle the kiln sitter, with no success. Finally, I decide I'd rather under-fire than over-fire my ware, so I shut off the kiln at about eight hours on High.
Unload today, and I see I'm about two cones cool--the sitter bar is just beginning to bend--and the bottom is definitely cooler than the top. I figure I've either got a broken element, or a dead switch, crippling both elements. So I do the match test.
The match test is perfect for the pyromaniacs among us. You start the kiln, turn the element switch you're testing to high, then walk away for five minutes or so. When you come back, take a stick match and carefully touch the head to the bottom element of the ring. If it bursts into flame, blow it out, and test the top element with a fresh match. If that one burns too, switch off the ring and test the next one.
In this case, I don't even need the matches. With power on and switch on high, the bottom ring is dead cold. So I switch off the breaker and open up the bottom circuit box, expecting to need a new $80 switch tomorrow. It turns out to be something much simpler.
When my kiln was built, modular and plug-and-play were industry catchphrases. Skutt pioneered the idea, and Cress followed suit. Kilns were built in nine-inch (two fire brick) high rings, each with two elements wired to one switch in a modular circuit box that plugged into the ring above and/or below. Three rings high made a standard 27-inch kiln. The circuit boxes connected with a standard 250 volt, 20-amp Leviton three-prong plug.
Remember my first repair entry title, Bad design? Yeah, again. Every time you fire your kiln, the bricks expand and inch the plugs apart a millimeter or two, but don't pull it back together afterward. Eventually, the gap is big enough that the current arcs, and burns out the female side of the plug. After replacing the top ring plug two or three times, I finally gave up and hard-wired the top and middle rings together. I kept waiting for the bottom one to fail, so I'd replace it the same way.
Fifteen years later, it finally did.
I suppose I'm impressed. The top plug only lasted six months or so. And again, another six months. The bottom one finally gave way when one of the blades burned in two. I also discovered, as I took it apart, that the bottom connector wasn't grounded; the hot leads led to the switch, but the ground wasn't connected to anything. I remedied that as well.
Now could I please not need to fix anything for a while?
Second firing since the last repairs. First one went perfectly, this one, not. In a normal firing, after time spent warming up the kiln--lid open, lid half-closed, switches on Low or Medium--I'll eventually close the lid, set all the switches to High, and in around six or seven hours, the kiln will reach temperature, the cone will bend, and the kiln sitter shut down.
Friday night around 10:30 pm, I went to check that the kiln had shut down. Nope. Glowing orange hot, though, so I thought we were close. 11:30, still no joy. Bottom peep hole isn't glowing as brightly as the top, though. I wiggle the kiln sitter, with no success. Finally, I decide I'd rather under-fire than over-fire my ware, so I shut off the kiln at about eight hours on High.
Unload today, and I see I'm about two cones cool--the sitter bar is just beginning to bend--and the bottom is definitely cooler than the top. I figure I've either got a broken element, or a dead switch, crippling both elements. So I do the match test.
The match test is perfect for the pyromaniacs among us. You start the kiln, turn the element switch you're testing to high, then walk away for five minutes or so. When you come back, take a stick match and carefully touch the head to the bottom element of the ring. If it bursts into flame, blow it out, and test the top element with a fresh match. If that one burns too, switch off the ring and test the next one.
In this case, I don't even need the matches. With power on and switch on high, the bottom ring is dead cold. So I switch off the breaker and open up the bottom circuit box, expecting to need a new $80 switch tomorrow. It turns out to be something much simpler.
When my kiln was built, modular and plug-and-play were industry catchphrases. Skutt pioneered the idea, and Cress followed suit. Kilns were built in nine-inch (two fire brick) high rings, each with two elements wired to one switch in a modular circuit box that plugged into the ring above and/or below. Three rings high made a standard 27-inch kiln. The circuit boxes connected with a standard 250 volt, 20-amp Leviton three-prong plug.
Remember my first repair entry title, Bad design? Yeah, again. Every time you fire your kiln, the bricks expand and inch the plugs apart a millimeter or two, but don't pull it back together afterward. Eventually, the gap is big enough that the current arcs, and burns out the female side of the plug. After replacing the top ring plug two or three times, I finally gave up and hard-wired the top and middle rings together. I kept waiting for the bottom one to fail, so I'd replace it the same way.
Fifteen years later, it finally did.
I suppose I'm impressed. The top plug only lasted six months or so. And again, another six months. The bottom one finally gave way when one of the blades burned in two. I also discovered, as I took it apart, that the bottom connector wasn't grounded; the hot leads led to the switch, but the ground wasn't connected to anything. I remedied that as well.
Now could I please not need to fix anything for a while?