TonyC Posted October 13, 2019 Report Share Posted October 13, 2019 As noted, I have an L&L e23S-3 kiln which I recently fired to cone 6. Settings were: Cone 6 Slow Glaze (pre-programmed), 1 hr 30 min preheat, no hold The final reading showed 2236 F, but both my Cone 7 witness cones slumped (more on top shelf). I am attaching photo. (Reference: witness cones front - bottom shelf Cone 7 far right, witness cones back - top shelf Cone 7 far left) I know I can adjust the CNOS, but have a basic question regarding the kiln at higher temps. I ran the Cone 06 bisque earlier in the week and it was perfect; both the temp recorded and witness cone results. However, this is the second time that I noticed a variance when I ran to the hotter Cone 6. Is that normal for a kiln to lose some of its accuracy at higher temps? Based on this, is it time to make the CNOS adjustment? If so, is there a "rule-of-thumb" regarding incremental changes? My initial reaction is 10 degrees based on the witness cone 7 results (setting 9910), but would appreciate any insight. Thank you. Link to comment Share on other sites More sharing options...
Bill Kielb Posted October 13, 2019 Report Share Posted October 13, 2019 1 hour ago, TonyC said: As noted, I have an L&L e23S-3 kiln which I recently fired to cone 6. Settings were: Cone 6 Slow Glaze (pre-programmed), 1 hr 30 min preheat, no hold The final reading showed 2236 F, but both my Cone 7 witness cones slumped (more on top shelf). I am attaching photo. (Reference: witness cones front - bottom shelf Cone 7 far right, witness cones back - top shelf Cone 7 far left) I know I can adjust the CNOS, but have a basic question regarding the kiln at higher temps. I ran the Cone 06 bisque earlier in the week and it was perfect; both the temp recorded and witness cone results. However, this is the second time that I noticed a variance when I ran to the hotter Cone 6. Is that normal for a kiln to lose some of its accuracy at higher temps? Based on this, is it time to make the CNOS adjustment? If so, is there a "rule-of-thumb" regarding incremental changes? My initial reaction is 10 degrees based on the witness cone 7 results (setting 9910), but would appreciate any insight. Thank you. Before commenting, I would like to know the total time your kiln took for each firing. Most kilns are marginally powered so as their capacity decreases the firing times increase. At some point, usually when the elements degrade by 10% or so (150- 200 firings give or take) the kiln will have more difficulty in making exact cone temps. Why? Well in the last 250 degrees of the firing the kiln needs to go about 100 degrees per hour for the cone to bend where expected. If it can’t do this because of capacity loss then it struggles to make the cones bend appropriately. The slow glaze program I believe should have completed in 7 hours and 37 minutes. How far away were you from this timeframe? Finally to answer your question you can put in an offset in to compensate but at some point if a wear issue your kiln will likely be inconsistent from bisque to glaze and when worn enough will eventually give you a rate error. The question becomes, how worn are your elements? If not at all, then dial in your offsets to get your kiln calibrated. I looked this up and it appears to have protection tubes over the thermocouples so there are already thermocouple offsets built in. Don’t know them by heart, but they are important and your thermocouple placement in the tube is also important. Any chance any maintenance has been done prior to the kiln beginning to over fire? Link to comment Share on other sites More sharing options...
TonyC Posted October 13, 2019 Author Report Share Posted October 13, 2019 31 minutes ago, Bill Kielb said: Before commenting, I would like to know the total time your kiln took for each firing. Most kilns are marginally powered so as their capacity decreases the firing times increase. At some point, usually when the elements degrade by 10% or so (150- 200 firings give or take) the kiln will have more difficulty in making exact cone temps. Why? Well in the last 250 degrees of the firing the kiln needs to go about 100 degrees per hour for the cone to bend where expected. If it can’t do this because of capacity loss then it struggles to make the cones bend appropriately. The slow glaze program I believe should have completed in 7 hours and 37 minutes. How far away were you from this timeframe? Finally to answer your question you can put in an offset in to compensate but at some point if a wear issue your kiln will likely be inconsistent from bisque to glaze and when worn enough will eventually give you a rate error. The question becomes, how worn are your elements? If not at all, then dial in your offsets to get your kiln calibrated. I looked this up and it appears to have protection tubes over the thermocouples so there are already thermocouple offsets built in. Don’t know them by heart, but they are important and your thermocouple placement in the tube is also important. Any chance any maintenance has been done prior to the kiln beginning to over fire? Total time was 10 hr 28 min. This is with a 1 hr 30 min preheat. Therefore ~9 hours if we back out pre-heat. I know that it can vary based on how full it was and the radiant energy generated. I have logged that my previous slow glaze firing on Aug 18 took 7 hr 34 min (but there was no preheat). This variance to my recent firing is worth noting, especially since both final temps reached 2236 F. As for the elements, they are new. I changed them (and thermocouples) when I bought the "used" kiln with only 63 firings total. I am now at 85 firings total (22 on new elements). As for the offset, the L&L has a built in offset (I think 18 degrees) to compensate for the tubes. I'd need to double check. Any CNOS adjustment would be additional to this value and programmed separately. Link to comment Share on other sites More sharing options...
Bill Kielb Posted October 13, 2019 Report Share Posted October 13, 2019 1 hour ago, TonyC said: Total time was 10 hr 28 min. This is with a 1 hr 30 min preheat. Therefore ~9 hours if we back out pre-heat. I know that it can vary based on how full it was and the radiant energy generated. I have logged that my previous slow glaze firing on Aug 18 took 7 hr 34 min (but there was no preheat). This variance to my recent firing is worth noting, especially since both final temps reached 2236 F. As for the elements, they are new. I changed them (and thermocouples) when I bought the "used" kiln with only 63 firings total. I am now at 85 firings total (22 on new elements). As for the offset, the L&L has a built in offset (I think 18 degrees) to compensate for the tubes. I'd need to double check. Any CNOS adjustment would be additional to this value and programmed separately. Sounds reasonable. Just to check the thermocouple is all the way in touching the end of the protection tube. Given all that, I would say offset. There are other considerations with respect to how your controller was set up, one being the relay switching speed and the other being the priority of how the zone control determines when to consider a segment finished. And still other things you could confirm such as actual operating voltage etc.... Factory specs on all this would be my next suggestion just to check and confirm they have not been altered but it sounds like you are ready to dial in offsets as the next logical step to even things out. Others may have thoughts and Neil sells these things so maybe he will weigh in. Link to comment Share on other sites More sharing options...
TonyC Posted October 13, 2019 Author Report Share Posted October 13, 2019 1 minute ago, Bill Kielb said: Sounds reasonable. Just to check the thermocouple is all the way in touching the end of the protection tube. Given all that, I would say offset. There are other considerations with respect to how your controller was set up, one being the relay switching speed and the other being the priority of how the zone control determines when to consider a segment finished. And still other things you could confirm such as actual operating voltage etc.... Factory specs on all this would be my next suggestion just to check and confirm they have not been altered but it sounds like you are ready to dial in offsets as the next logical step to even things out. Others may have thoughts and Neil sells these things so maybe he will weigh in. Thanks for taking the time to explain things. I will consider each item. Much appreciated. Link to comment Share on other sites More sharing options...
neilestrick Posted October 13, 2019 Report Share Posted October 13, 2019 4 hours ago, TonyC said: Total time was 10 hr 28 min. This is with a 1 hr 30 min preheat. Therefore ~9 hours if we back out pre-heat. If you're using the preheat function, it takes approximately two hours to get to 200F (60F/hr climb) before it starts the hold time you programmed. So about 7 hours if you back out the preheat, which means your firing time was not too long. If anything it went a little fast. There's always some variation, though, so I wouldn't worry about that. I'd do the cone offset. Start with 10 degrees like you were thinking. The 18 degree offset is in the thermocouples, not the cones, so you won't see that when you do the programming. The rule is do a thermocouple offset when it's inaccurate at all temps, do the cone offset when it's only off for the cone you're firing to. It may very well be off at cones 5, 7 and 8, too, but if you don't fire to 5, 7 or 8 it doesn't matter. Since it's correct at bisque temps you should do the cone offset. Link to comment Share on other sites More sharing options...
TonyC Posted October 14, 2019 Author Report Share Posted October 14, 2019 4 hours ago, neilestrick said: If you're using the preheat function, it takes approximately two hours to get to 200F (60F/hr climb) before it starts the hold time you programmed. So about 7 hours if you back out the preheat, which means your firing time was not too long. If anything it went a little fast. There's always some variation, though, so I wouldn't worry about that. I'd do the cone offset. Start with 10 degrees like you were thinking. The 18 degree offset is in the thermocouples, not the cones, so you won't see that when you do the programming. The rule is do a thermocouple offset when it's inaccurate at all temps, do the cone offset when it's only off for the cone you're firing to. It may very well be off at cones 5, 7 and 8, too, but if you don't fire to 5, 7 or 8 it doesn't matter. Since it's correct at bisque temps you should do the cone offset. Thanks Neil for the validation. I will occasionally run a Cone 5, but otherwise, simply 6. I just checked my records and on June 30th I ran cone 5. The program states 2165 F temp, and the actual was 2177 F. I didn't leave any comments on the witness cones, so I assume nothing dramatic showed, but isn't there a 30 degree window between cone differences? So I should at least measure again, but maybe offset cones for Cone 5 as well. Thanks for the input. T Link to comment Share on other sites More sharing options...
TonyC Posted October 14, 2019 Author Report Share Posted October 14, 2019 4 hours ago, neilestrick said: If you're using the preheat function, it takes approximately two hours to get to 200F (60F/hr climb) before it starts the hold time you programmed. So about 7 hours if you back out the preheat, which means your firing time was not too long. If anything it went a little fast. There's always some variation, though, so I wouldn't worry about that. I'd do the cone offset. Start with 10 degrees like you were thinking. The 18 degree offset is in the thermocouples, not the cones, so you won't see that when you do the programming. The rule is do a thermocouple offset when it's inaccurate at all temps, do the cone offset when it's only off for the cone you're firing to. It may very well be off at cones 5, 7 and 8, too, but if you don't fire to 5, 7 or 8 it doesn't matter. Since it's correct at bisque temps you should do the cone offset. Just checking....the proper setting to shut the temp down 10 degrees lower is 9910, correct? Link to comment Share on other sites More sharing options...
Bill Kielb Posted October 14, 2019 Report Share Posted October 14, 2019 6 hours ago, TonyC said: Just checking....the proper setting to shut the temp down 10 degrees lower is 9910, correct? Sorry, Just saw this post but I believe negatives are 90, so 9010. A copy of an old Bartlett manual below. You can get a fresh one from the Bartlett control site if necessary. Link to comment Share on other sites More sharing options...
TonyC Posted October 14, 2019 Author Report Share Posted October 14, 2019 3 hours ago, Bill Kielb said: Sorry, Just saw this post but I believe negatives are 90, so 9010. A copy of an old Bartlett manual below. You can get a fresh one from the Bartlett control site if necessary. Awesome, thank you! Link to comment Share on other sites More sharing options...
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