Arnold Howard, on 07 March 2013 - 09:26 AM, said:
I have heard of electrical fires that involved a kiln. But I have never heard of a fire caused by the heat from a properly installed kiln. If a kiln overfires, the elements eventually burn out, and the kiln then cools down. But the heat is contained within the kiln.
When the kiln is not in use, the lid should be kept closed. We also advise disconnecting the power.
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Ditto. Every fire I have heard of came from the wiring in the walls, the plug, or from something combustible being too close to the kiln. A properly installed kiln cannot melt down. Sticky relays are somewhat of an issue, but the odds of more than one sticking are extremely
low. The only time I have seen a sticky relay cause overfiring was on a 18" tall kiln going to cone 06 where one of the two relays stuck. Even then it did not melt the clay, just made the glazes run a bunch. The most damage happens when the clay melts and flows into the bricks.
On a 27" tall, 3 relay kiln, if one relay sticks it will just prevent the kiln from cooling completely. It usually hangs out around 1400 degrees or less depending on the size of the kiln. If two relays from neighboring rings of the kiln stuck it could cause those areas of the kiln to overfire a bit if the shelves were tight, but not likely enough to puddle a cone 6 clay. I think at worst you would only ruin shelves. You're probably more likely to win the lottery than have 2 relays stick at the same time. Zone control comes in handy here because it's easy to see if a section is running hot, and once a section gets too hot you'll get an error code that will shut down the firing.