Sputty Posted June 16, 2017 Report Share Posted June 16, 2017 . Link to comment Share on other sites More sharing options...
Roberta12 Posted June 16, 2017 Report Share Posted June 16, 2017 Have you checked your relays? Roberta Link to comment Share on other sites More sharing options...
Sputty Posted June 16, 2017 Author Report Share Posted June 16, 2017 . Link to comment Share on other sites More sharing options...
ayjay Posted June 16, 2017 Report Share Posted June 16, 2017 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. Only guessing here, (I've not yet worn out any elements) but as you have less element material than in a larger kiln wouldn't the effect of deteriorating elements tend to show up much quicker? Link to comment Share on other sites More sharing options...
Sputty Posted June 16, 2017 Author Report Share Posted June 16, 2017 . Link to comment Share on other sites More sharing options...
Dick White Posted June 16, 2017 Report Share Posted June 16, 2017 In my experience, the drawing out of the firing time is more gradual as the elements age gracefully. The sudden decline is worrisome, but I don't what else to test other than ohms of resistance. The conventional wisdom of resistance testing is that a measured resistance of more than 10% over specification indicates worn elements. However, you don't have a factory specification (yet) so no reference point to determine failure. When the new elements are installed, take a resistance measurement and write that down in your kiln manual so you have it for future reference. Link to comment Share on other sites More sharing options...
Sputty Posted June 16, 2017 Author Report Share Posted June 16, 2017 . Link to comment Share on other sites More sharing options...
Guest Posted June 16, 2017 Report Share Posted June 16, 2017 I'm not the resident expert on this but is it possible that the elements need to be replaced? Link to comment Share on other sites More sharing options...
Sputty Posted June 17, 2017 Author Report Share Posted June 17, 2017 . Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted June 17, 2017 Report Share Posted June 17, 2017 It's a strange one, let's hope it's the elements. Link to comment Share on other sites More sharing options...
GEP Posted June 17, 2017 Report Share Posted June 17, 2017 How many elements are in this kiln? When my elements are getting old, the firing time gets longer slowly. When one of my elements has failed (element breaks and melts into a little puddle at the break) the firing time gets dramatically longer all of a sudden. If there is more than one element, losing one will cause this behavior. Link to comment Share on other sites More sharing options...
Sputty Posted June 17, 2017 Author Report Share Posted June 17, 2017 . Link to comment Share on other sites More sharing options...
GEP Posted June 17, 2017 Report Share Posted June 17, 2017 How many elements are in this kiln? When my elements are getting old, the firing time gets longer slowly. When one of my elements has failed (element breaks and melts into a little puddle at the break) the firing time gets dramatically longer all of a sudden. If there is more than one element, losing one will cause this behavior. There are 3 elements, although each one sort of doubles back on itself, so a quick glance into the kiln looks like there are 6. They are wired in series, so if one fails completely, there's no circuit at all. However, during the last (half a) firing, I tested the voltages across each segment, and they were even across the 3 elements. If one element had gone 'a bit' bad (but not catastrophically), there would be a clue in an uneven voltage drop across one segment. No such luck. It's the suddenness of the lengthening of firing time that puzzles me. To go from 8 hours to 12 hours in the course of 3 firings seems odd. I had been hoping that it was a line voltage problem - I live rurally in France, where we are prone to... erm... variation. But it's fine - I checked all the way through the last firing. I even racked my brains to try to remember if I'd included anything unusual in the kiln, which might have fumed and done mysterious instantaneous damage to the elements, but I really haven't. When the new ones arrive, I'll check the resistance of one, and put that against the resistance of one coming out of the kiln. That should tell something, at least. Gotcha. Yup you're right that's a different configuration from my elements. I have six elements, they are wired together in pairs, so three different circuits. Curious to hear the resistance comparison between new elements. Let us know! Link to comment Share on other sites More sharing options...
neilestrick Posted June 19, 2017 Report Share Posted June 19, 2017 How many elements are in this kiln? When my elements are getting old, the firing time gets longer slowly. When one of my elements has failed (element breaks and melts into a little puddle at the break) the firing time gets dramatically longer all of a sudden. If there is more than one element, losing one will cause this behavior. However, during the last (half a) firing, I tested the voltages across each segment, and they were even across the 3 elements. If one element had gone 'a bit' bad (but not catastrophically), there would be a clue in an uneven voltage drop across one segment. No such luck. A change in element resistance won't affect the voltage. It'll still measure the same voltage regardless of the resistance change. The difference will be in how hot the element gets. You need to measure the element resistance. If the relay stays on for most of the firing, that tells me that this kiln may under-powered for the temp you're firing to, and so a little change in element resistance will have a big effect on its ability to get to temperature. Have you changed the thermocouple? Link to comment Share on other sites More sharing options...
Sputty Posted June 19, 2017 Author Report Share Posted June 19, 2017 . Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted June 19, 2017 Report Share Posted June 19, 2017 No need to take elements out to measure resistance. I did hear you can take off the neutral connection if you are getting strange readings but I just put the probes where they entered/exited the kiln to measure when they are installed. Have you opened the controller to see if any components are looking suspect? Link to comment Share on other sites More sharing options...
Sputty Posted June 20, 2017 Author Report Share Posted June 20, 2017 . Link to comment Share on other sites More sharing options...
neilestrick Posted June 20, 2017 Report Share Posted June 20, 2017 If an element measured different voltage because of a change in resistance, then 22 ohm elements would measure different voltage than 30 ohm elements. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.