fergusonjeff Posted March 18, 2022 Report Share Posted March 18, 2022 This question is mainly for Neil, but happy to get other feedback. I shut off my Bisque firing this morning before completion and am trying to understand the problem. I am using a 10 cubic ft L&L eQ2827 with digital control and 3 thermocouples. Typically during firing the top and bottom sections work the hardest and the middle operates at lower power. I was firing a cone 04 bisque on the slow bisque setting. I usually leave an inch or so of space around the thermocouples, but because I was trying to fit a lot into the firing for an upcoming wood firing I know I got a piece or two and also a shelf very close to the middle thermocouple. The bottom had the usual 1" or so and the top had nothing close. After a long preheat (some items were still not completely dry) I noticed the kiln was really slow the climb and the middle element was running at 100% while the top and bottom were ~30%. I thought this might be due to the object close to the middle thermocouple causing it to sense too low a temp. I figured it might even out as temps got higher. I checked every few hours and the same energy distribution persisted and the middle was reading ~80 degrees F lower than top and bottom. It was also very slow. I think it was at around 30 hours when I finally shut it off this morning and the projected firing time was well over 40 hours more than double the usual time). The temp readings were around 1300F. My initial concern was that it was actually much hotter and there was some temperature reading error. I stuck my thermocouple from my wood kiln and got a reasonably close reading to 1250F. All sections were a uniform dark red glow when I shut them off. I have put items close the the thermocouples before and not had this kind of problem. Any other possible causes? I am planning to let it coll and reload with more space around the middle. Is there some other more systematic issue that I could be missing? Thanks for any help. Link to comment Share on other sites More sharing options...
Bill Kielb Posted March 18, 2022 Report Share Posted March 18, 2022 Since all sections were glowing, assuming crowding the thermocouple was not an issue, if you loaded the kiln very densely in the middle it will load that area more so than top and bottom. Aside from that I would make sure the center tcouple is accurate and all the center elements are actually working Link to comment Share on other sites More sharing options...
fergusonjeff Posted March 18, 2022 Author Report Share Posted March 18, 2022 Thanks. All sections seemed to be glowing about the same. It was a pretty even load except for the very top. I had a few large vases that are tightly packed but the area around the upper thermocouple was fairly open. Link to comment Share on other sites More sharing options...
neilestrick Posted March 19, 2022 Report Share Posted March 19, 2022 @fergusonjeff Were all the elements glowing with heat, or just the sections in general? Sounds to me like the middle section wasn't actually heating, it was just getting its heat from the top and bottom, probably because of a dead relay in the middle section. The controller was trying to get it to heat more, hence the 100% output, but nothing was actually happening there. If it was actually running at 100% then it would have been wicked hot in the middle. That kiln has a lot of power, so the top and bottom were able to carry the load just enough to keep it from erroring out, but not heating as fast as it should. Packing too close to a thermocouple shouldn't cause that big a problem. Link to comment Share on other sites More sharing options...
fergusonjeff Posted March 19, 2022 Author Report Share Posted March 19, 2022 Thanks Neil. I think you have figured it out. Is there any diagnostic that will confirm a bad relay? With my older kilns the relays always failed in the in position causing over firing. Link to comment Share on other sites More sharing options...
fergusonjeff Posted March 19, 2022 Author Report Share Posted March 19, 2022 Just checked what the kiln computer provides as “relay diagnostics”. All it is is a cycle counter not any actual diagnostic. All the relays had about 300,000 cycles. Link to comment Share on other sites More sharing options...
neilestrick Posted March 19, 2022 Report Share Posted March 19, 2022 7 minutes ago, fergusonjeff said: Just checked what the kiln computer provides as “relay diagnostics”. All it is is a cycle counter not any actual diagnostic. All the relays had about 300,000 cycles. You can either check the outputs on the relay with a meter, or put a little piece of paper on the elements for that section and start the kiln and see if the paper burns after a minute or two on full, or let it run for 5 minutes on full and crack the lid and see if the elements are glowing in that section. Link to comment Share on other sites More sharing options...
fergusonjeff Posted March 19, 2022 Author Report Share Posted March 19, 2022 Just checked what the kiln computer provides as “relay diagnostics”. All it is is a cycle counter not any actual diagnostic. All the relays had about 300,000 cycles. put paper on each section and top and bottom burned. Middle stayed cool. Link to comment Share on other sites More sharing options...
neilestrick Posted March 19, 2022 Report Share Posted March 19, 2022 2 hours ago, fergusonjeff said: Just checked what the kiln computer provides as “relay diagnostics”. All it is is a cycle counter not any actual diagnostic. All the relays had about 300,000 cycles. put paper on each section and top and bottom burned. Middle stayed cool. Yep, middle one is out. If they've all been in there for a couple hundred firings or more, change them all. Get THESE. Minimum life on relays is 100,000 cycles at full voltage, so I'd go ahead and replace them all. Link to comment Share on other sites More sharing options...
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