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Element resistance vs heating the kiln


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This is a question for the knowledgeable electrical engineers in the audience. I am trying to remotely help an acquaintance far across the pond who is having trouble with her kiln taking too long and tossing E1 errors. There are no proper kiln technicians in her area, so she must rely on a local sparky to do the necessary maintenance and repairs. We have been tossing ideas back and forth, including information reported to her by the sparky. One issue is her house appears to be suffering some voltage drop, but a review of the log of a full power test shows a severely lagging ramp of between 30 and 40℉/hour above 2000℉. That tells me the elements are shot. She claims they are only a year old and not many firings, but then she dropped a comment that sent me scratching my head. The sparky, seeing that the resistance of the elements was increasing (a sign of decreased amps/watts being pulled) and "corrected" that by shortening the elements until the resistance went down to original spec. I am thinking a serious WTF was he doing, but please, one of you who really knows what you are doing, am I nuts or is the local sparky nuts? I understand the Ohm's Law calculation, but my less-than-complete understanding of kanthal elements is that the amount of heat radiated is a function of the surface area of the wire. As the wire oxidizes and wears over usage, the diameter of the wire decreases, thus decreasing the surface area, and consequently the heat radiated. The measured increase in resistance, thence transferred through the Ohm's Law calculation to watts of power, is merely a proxy by which we can estimate the degradation of the heating power of the elements, and shortening the element to decrease its resistance is doubly counterproductive to heating the kiln. Please help me help her. Thanks!!!

dw

Edited by Dick White
corrected a word
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52 minutes ago, Dick White said:

and shortening the element to decrease its resistance is doubly counterproductive to heating the kiln. Please help me help her. Thanks!!!

No, in a pinch it will work. Watts are king as that is the energy put into the kiln so as elements wear their resistance rises and of course ohms law tells us less watts. Surface area is not the culprit it’s less watts for heating. So one way to make this work again is to neatly shorten the element back to design resistance and therefore back to the original wattage.

obviously doing this has a downside as the element will continue to wear, even quicker and likely fail by burning open. At some point there will be insufficient element material and it will just fail.

As a stopgap, probably Ok but definitely will wear out quicker and / or fail.

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