Bill Kielb

Sorry to hear that actually. 3% rule of thumb here is usually allowed but for kilns for obvious capacity reasons less is suggested. No point in starting with a brand new kiln in effect worn 3%. There is a special rule for continuous resistive loads to protect the breakers from repeated heating in North America. The rule here would be no less than 125% of the rated load and not to exceed 150%. Often this takes care of the voltage drop issue, a nice side benefit. Most countries address these loads similarly to protect the protection devices so you may want to research. Electricians not used to working on kilns are often not familiar and tend to under size things. Most often the rules for maximum loading on a breaker fit well with this standard. So for example, here for normal breakers you are only allowed to size them so normal loading does not exceed 80% of the rating. Which, interestingly is the reciprocal of 1.25 or 125%. Actually intuitively who would put a 30 amp load on a 30 amp breaker? It does happen though. For your use you may want to have elements re-wound to make the original wattage at your rated voltage. (Total kiln R= V(squared) / Watts) Of course all protection and wiring would need to be upgraded as necessary and I would suggest clear re-labeling is a must. BTW we just went through this in another thread and as an FYI, kilns with 4 watts per interior square inch are usually most robust. Hope that helps! Previous thread : https://community.ceramicartsdaily.org/topic/30261-paragon-dtc-800-kiln/?do=findComment&comment=228236

Probably the most important part - your method works for you. I will say that excess pressure out the lower burner port lines up with a bit too much restriction or reflected flame in the flame path, especially if your kiln is not pressurizing from the top down. Under normal circumstances folks find a suitable gas pressure then begin closing their damper very slowly until some pressure (flame) exits the lower spyhole and they are in heavy reduction. With the restriction in the flame path it sounds like you will need to free this up a bit, it likely is too restrictive. One thing at a time though.

My feeling is the burner port size confirms you were going in reduction because of lack of secondary air. And the better performance seems to support that result as you were able to fire faster because your burners put out more. subjectively, To me I like the use of a shelf as your bag wall so it becomes a glowing red hot radiant panel and enlarges your flame trench a bit especially in a small kiln. I like the wall to be significantly less mass that the wares in the kiln. Also to me my next try would be with the target brick to the right or up against the right hand wall to provide some deflection forward and because of the coanda effect it still will drive about 1/2 the flame to the rear and to the right wall of the kiln. One thing for sure, I have rarely been able to solve by changing multiple things. It’s often too dynamic so unless you get lucky with first placement it makes things really hard to solve. So whatever changes are made I think one at a time is the most effective way to creep up on a solution.

just to keep the brewmasters at bay: I think that’s a really solid assumption. It can be less for a mixture of things in water but those things would need to be a lower sg and miscible in water. A real world common example likely would be alcohol. For clay, I can’t think of anything light enough so to speak.

This might help - the desired sg is the one that works best for a glaze and an application method. Often it’s tested and recorded once known. I like a three second dip, others prefer differently. Additionally for a clear glaze for example I like them applied as thin as practical and with a uniform 100% coverage. So desired sg to me is dependent on what’s being applied and application method as well as desired thickness. In other words It’s usually a recorded number for a particular product based on experience

Just an FYI, he also has low voltage. 228v fully loaded. Probably needs that stabilized before you tune the loop

Yep, definitely makes sense to read the nameplate.

Nope probably very high. Best to read the nameplate of the kiln but I think he picked orifices that translate to 90k btu per burner and 8 burners based on a previous size of #28. Reading the nameplate would be best and not working in PSI also really could be relevant here IMO

The circuit breaker will likely tire at some point from the heating. Best case it will trip prematurely, worst case is it will fail to trip until a higher amperage. Probably not a good idea to wait too long to get it wired properly.

Experimentation is good, my thought is maybe start at 5:1 or high fours. Your alumina levels are relatively high, I get it, it’s easy to get your ratio that way but at some point it isn’t gonna melt. As an example: For cone six glazes I like to stay 0.58 Al or less, they generally are fairly stiff in this range in my experience. 0.45 boron is great at cone 04, increasing can create its own issues so if you follow the Katz research 0.45 for cone 04 is great, exceeding it, especially in excess often is not considered better. Those glazes have a large amount of clay as well so not entirely sure how they will mix up. Feldspars are a nice source of silica, alumina and fluxes as well, not sure if you have a pure preference to clay and Frits In the end thoughtful experimentation is great though so note your results. You may be able to find some already made mattes on Glazy or elsewhere to experiment on as well than just creating one from scratch. Right now, you really don’t have glazes that require silica as it’s entirely sourced from the materials. You may be able to create simpler allowing for the addition of some silica.

Color response can be a thing as well with use of certain fluxes. I would suggest (in a well melted glaze) a test blend by varying the Si:Al from 4:1 to 7:1 for a true matte just to get a feel of going from let’s say dry matte toward semi gloss or gloss is a worthwhile exercise to experience IMO.

Yes, you guessed it watts per cu ft of available load plus watts per sf to offset shell surface losses. Most kilns have about 110% brand new and after wearing 10% they need element replacement to make it. Cone 6 kilns often have less than their counterparts. This is the norm, not a lot of kilns are made with 115% capacity new. So you are indeed fortunate. Reaching cone 7 with a hold makes total sense this way. Operating your elements at top temp though with a hold will shorten their life a greater percentage than just normal operation. How much is relevant to how over designed the kiln is. At 3 watts per square inch, life is short. 3.5 w / sq in, better, sort of typical. 4 watts per square in- you are in the longevity bonus range. L&L has great published data comparing the loading as well as the effect of 3” brick

You can just buy it, a common circuit board etching solution. Chlorine gas release (mustard gas would be primary concern) If you make it, it does not need to evaporate but does require oxidation with peroxide or bubbling air as a final step. Etched a lot of circuit boards as a kid, use all reasonable care.

Here is a little engineering fun that could spark some additional thought. The more laminar, the better. One can do tricks with laminar flow. A fun practical example, 14:02 is probably most relevant. https://youtu.be/y7Hyc3MRKno

OMG! The one thing guaranteed to overfire your stuff! I assumed it came programmed with the kiln. Setting an R type thermocouple and using another type in its place is one sure way to over fire. Really good catch, a well known issue that happens on occasion and most manuals even warn of it. It’s rare to happen and really hard to figure out unless it’s obvious someone was in there changing it. Nice! And you got a lot of experience too. Just be sure to confirm what type you have.

If it was 100% unattached there would no reading, so maybe, definitely tighten and make good. Thermocouples increase in output as temperature goes up so a bad connection could give you a low reading but that would really speed up the firing because the controller would think it’s lower and fire harder. At 9.9 ohms (10%) your elements would be considered fully worn, so depending on the accuracy of your meter they don’t seem fully worn although 9.4 is halfway there. Can you safely measure the voltage: Kiln off and kiln fully on just to see if we are losing a percentage energy there. It doesn’t take much so worth measuring I think. We also need to know the rated voltage and wattage on the nameplate to compare with the measurement. Good find on the tcouple, but doesn’t seem likely that that would logically account for the symptoms. All else fire a test load, maybe some test bowls, add some mass as in shelves just to get closer to a normal load. It’s troubling because you have not fired a full load yet and your symptoms are, it is slowing above 1170. The good thing is you can monitor the speed and see if it slows down near the end. If so, we will need to find where the power loss is. Voltage measurement (kiln operating- all elements) for sure if you can safely do it. If the voltage is low that will be significant.

Maybe, but the thermo couple slows down after 1170 and displays room temp ok but fails a 25C correction. Her comment was an observed 15 minute delay which is much like a 15 minute hold even with a 25c depressed final temp.. Firing rates don’t slow down if the thermocouple is miscalibrated. She seams to bisque Ok, not necessarily over fire in the bisque because the controller or thermocouple is off. I think her symptoms point to being under powered so checking would be wise. I have reasons for what I see, I really don’t see anything that contradicts the progression. Under powered can be elements, relay, connection, voltage so I think its wise to check. Not sure why anyone would discourage it actually?

She programmed 60c per hour and it does not follow that in the final segment of firing. See original post.

I think smart to check the elements but also, have you checked that they all are glowing and one set is not out? You did a lot of the hard work by confirming that the kiln was slowing down especially at the top temperatures, you reasonably verified the thermocouple is reflecting room temperature and proven as best you can that even when lowering the endpoint temperature from 1220 to 1190 the kiln still over fires because it takes more time than programmed. That you did these things is quite impressive actually, but they point to not enough power available at the top temperature. You can’t recalibrate or offset your controller to make it fire faster and you have already offset by 25c and only improved things slightly. All things point to reduced power or or an element not working, it’s logical now to test why you do not have enough power at top temperature. I think everyone understands that elements are expensive and are hoping for another fix including me. I think it’s time to find out why, hopefully you will find a loose connection or come back and tell us one relay was not working. Definitely make sure all connections are sound and in good order though, thermocouple or other. One thing we did not discuss and has been assumed is if it is operating at it’s required voltage so time to measure all that as well with your new meter. 1260c is cone nine, so this kiln ought to get 100 - 150 firings on an element set before it starts slowing down while reaching cone 6 temperatures and requires new elements. Generally 10% less power and kilns start to take more time until they simply can’t achieve a decent cone 6 glaze firing.

She programmed the last segment for 60c per hour but timing it realized it was off trac, not going 60c per hour and taking longer. So what we know is it could not achieve 60 c per hour once it got above 1170C, according to the OP tracking it. The kiln only exceeded time, not temps so far as we know. The cones reflect the heatwork which at this point appears to be the extra time spent during the final segment.

@Babs @neilestrick It was mysterious as her times and ramps seemed good especially at the end of firing, but when I asked if these were actual or just calculated she did watch this and explained: Hmm, I wonder if the elements are worn, as I set up a camera and checked the temp every hour against what it should have been. I found that the kiln follows the ramp spot on, until it gets to about 1170C and then it slows down, and added about an extra 15 mins to the total time” So it looks like she did the hard work and figured out the kiln runs out of speed at the top. I think worn or bad element connection, relay etc… is really likely. Recalibrating around one of those conditions is not very likely.

Your kiln appears to be 6226 watts or 25.9 amps, let’s call it 26 amps. 1/2 the power is from the top ring and 1/2 the power is from the bottom ring. So 26 amps/2 = 13 amps load on each infinite switch. The elements must stay in series (No neutral connected at this junction) and each series group gets fed from the infinite switch. H1 to one side of the element group and H2 to the other side. Sketch it up and post it just to be sure - folks here will double check. Notice a 40 amp fuse was required, today the breaker size is 125% of the load not to exceed 150% meaning 35 amps for todays breakers. This is a special requirement for kilns to make sure the breaker doesn’t overheat and wear out. You 30 amp breaker is undersized and this ought to have #8 wire run to it as well.

@Babs Hmm, not sure where this is going but if the kiln does not make 60c per hour in the final segment nearly empty it likely will degrade rapidly from there until no amount of extra time will make it work. If this is as it appears, calibrating may work for a short while but very likely won’t work on a full kiln. If true, It cant make a suitable rate empty, when full its rate likely will be unusable even with the best of recalibrating. Calibrating and compensating won’t make it fire faster at the top temperatures. All speculation though, And hopefully a minor problem like a set of elements out, bad relay, bad connection. I think finding out is the prudent course of action though.

@Dana StripeMost kilns will not do it. Generally a cone 10 kiln will get you 150-200 fittings at cone 6 before the elements wear by 10% or more and you simply can’t make cone 6 temperatures without a controller error or poorly fired glaze. Also your controller ought to be limited to 2250 peak temperature from the factory so getting to cone 7 would be tough. You have a rare performer. What model Skutt and how many watts?

This is great but I would encourage you to read the step by step guide from your state posted above its really done well. I think it will remove some of the scare factor. As far as accounting and taxes you will need to adopt real accounting practices regardless of the structure corporate or not so an accountant or your husband can make that a lot less challenging. Tax filings I always outsourced that, it’s not worth my time to learn tax accounting for various states.