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Showing results for tags 'Normality'.
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Sputty posted a topic in Equipment Use and RepairI have a small 3KW electric kiln I use for tests, or when I need something quickly. Normally, it will fire to cone 6 in 8 - 8 1/2 hours. Over the course of the last 3 firings, the firing time has stretched to 12 - 12 1/2 hours. The final temperature for these last few firings has been way below the nominal temp for cone 6, but fortunately I always rely on actual cones, which have eventually gone over... Is this normal? I've always assumed that elements gradually lose their mojo, slowly building up resistance. But this increase in firing time seems rather sudden to me - over the space of only 3 firings. The voltage to the kiln is good, and the voltage drop across each of the three elements is even, so presumably it's not that one has just gone a bit duff in its old age. All connections are solid. The elements themselves look a little aged, but don't yet have an abundance of that grey-pinky oxide that normally signifies retirement is close. I don't remember this happening prior to the last time I changed the elements, but that was a few years ago, so I could be wrong. I don't know what the resistance of the elements should be from new, so I've no way of knowing how much they've aged. (How much of an increase in resistance is considered terminal, anyway? Is there a figure?) Any comments? EDIT - the firing that is (was) going on as I type this has just returned an error F1 - the kiln cannot heat at a rate of 1 degree over 20 minutes. It got to 1140 deg C (2065 deg F), and plateaued. I've ordered some new elements!