Bill Kielb

if you have the time Posting the pictures mentioned above could go a long way to helping understand what is likely possible to help with your decision.

No, they cannot really be wired for less amperage. A 50 amp kiln requires more power than your present and is likely larger in size and needs more power to fire to temperature.. Post a photo, you likely can change the 30 amp circuit for a 50 amp so space may not be an issue as well unless you intend to try and run both kilns concurrently. Make sure you post the photo of your electric panel (context view) and the current 30 amp breaker. Also post the make and model of the kiln you intend to install. A picture of the equipment tag would be best. Folks here will look up and confirm the proper circuit size and wire size by the manufacture. Kilns are a bit of a specialty so not all electricians are familiar. Good to have a double check IMO. Finally, post a picture of any panel diagram and electric panel model information usually on thee inside of the door. It may be tandem rated which could be a reasonable way to free up space. If you have real fuses then you may be out of space and /;or at capacity. If you have breakers ( not fuses) then the photos will be very helpful.

my reference was for greenware. In my experience I have seen interesting/ unique spiral cracks occur where excess working / burnishing has taken place. My recollection is it was someone who wanted the perfect bowl interior and so would trim and heavily burnish the inside of the greenware. It looked great but the difference in density plus the propensity to cause -for lack of better words - local de-lamination made for some interesting circular or spiral failures upon firing. Saw this same failure at the bottom of several cups - same technique, almost too much trimming and aggressive burnishing to make it look super smooth. When fired and failed the failures appeared to be spiral or follow the circular path of the work that had been done pictures here might help a lot though. As far as density, compression …… I find clay most logical if I treat it like other material properties we accept. Compression is a real thing, real compression though. Clay memory to me is not a mysterious thing. If Crease a piece of paper, one side is stretched and the other compressed. If I stretch one side of something while throwing I have to work really hard to get everything back to the same uniform density and thickness otherwise it will return in the fired ware. Not really memory to me.

Straight from Digital fire via Glazy Looks like Custer is a sibling. Glaze Calc can be useful here if you have it else digital fire and Glazy have nice material databases.

Since most of your numbers look fine, my most likely guess would be a worn main breaker. For kilns in North America breaker sizing is usually no less than 125% of the connected load to no greater than 150%. This means prox 56 amps to 67 amps so 60 amps is a nice size. Resistance loads tend to heat up breakers so the rule is really to make sure the breaker is protected against overheating by oversizing them appropriately. Often breakers will wear and overheat more, a simple non contact thermometer is a nice way to check if it’s significantly hotter than similar like loaded breakers in the panel. A final confirmation would be to measure the amperage draw to confirm its in the range of 45 amps and then confirm the connections at the breaker are secure and not overheating the breaker themselves. Once you are confident it is not overloaded and the excess heating is coming from the internal connections within the breaker, time for replacement. Breakers for normal residential and commercial loads are generally limited by code to operating continuously at no more than 80% of their rating which is the reciprocal of 1.25. So it all makes sense really and the actual short circuit rating of a breaker is something other than the gross value of the breaker itself. These days you will see machinery with a minimum circuit amps (mca) and a maximum circuit breaker size specified. Anyway, my guess check the main circuit breaker to see if it is warm or hot after a few hours use. BTW 40c (104f):is the expected max ambient temperature. 104f feels slightly warm to the touch, not much above body temperature.

Yes, either between shelf posts or hung off the end of a half shelf. Never made a special holder, maybe only fired a handful as very custom gifts. The Kanthal wire was fairly thick though, 1/8” or bigger as I recall.

When we made them, it was easiest to hang them by one end while firing (Keeping them reasonably straight). From there a choice of a hole could be made in the handle and stay in the finished ware as decorative, or a sacrificial eyelet could be scored in advance and removed after firing yet ground perfectly smooth with a diamond pad. All of ours were porcelain, (Frost or standard 365 English porcelain) fully vitrified to 1% or less yet glazed for 99.9% of the chopstick. Decoration was typically carving and underglaze with a durable clear or ombre overglaze so often the white porcelain was visible in parts. .

@JohnS thanks! I would love to take credit but it is what Orton observed. It has helped me a bunch over the years though. Hopefully pass it along as you need.

So 1050c is a long bisque, (accurate IR to 1000c usually in the 500 usd range though ) my experience if you are comfortable with that approximate temp nothing has melted significantly. Generally clay fluxed reactions take place in the last 100c, last 200c should be pretty safe. I would finish the firing the sitter cone at this point should melt appropriate to the heatwork.

Thermo couples are literally like a battery, they generate very precise voltage for a given temperature. Lots of folks try to measure their resistance but this is not really a meaningful way to check them. One of many temperature and output charts online here: https://www.thermometricscorp.com/PDFs/type_s_tc_in_F.PDF This output voltage is very precise and defined so all thermocouples should track reasonably and precisely with their chart values. One easy characteristic folks take advantage of is their output at 32f (0C) and 212 f. So home testers will often check the output in an ice water bath and boiling water. For upper range general tests I have seen two clamped next to each other and torched to highest torch temp (probably 1200f - 1500f and compared against each other (two meters required ) Anyway, a way to do some meaningful testing. K type have a similar chart, just different voltage output at various temperatures. So easy to get some simple,tests done on these in a pinch.

I believe you, just have never seen it without physical or measurable damage. Just wondering how to test for the wear.

Thanks for the pictures, will just scan and see if I notice something, but they look pretty good. The sequence single zone anomaly and kiln stall could be tc related so that would be great if it works fine now. One thing I may have noticed in the picture goes to the wires that feed the kiln. I would expect this kiln to be on a 90 amp breaker and likely #3 wire run to it. It’s really hard to tell from the picture but the liquidtight flexible conduit appears to be 3/4” to which only one #3 wire would fit by code. I think it’s worth checking what size are these wires (are they under sized) , if undersized they could heat up significantly while running and potentially cause mysterious operation. I think it’s worth checking the main feeds are #3 or greater, and the flexible conduit is at least one inch (needed to cool them) and any temperature measurement that can be made from the kiln to the breaker, including the breaker with a non contact thermometer while this kiln is in operation could reveal these are at issue. Hard to Judge from a picture though, but worth double checking I think. Since this is a production kiln (pk), Skutt has designed this for 75c wire, so while a very obscure thing, it also has bearing on the rating of the wire and breaker terminals. If you can read the wiring labeling somewhere along the way it would be good to know it’s temperature rating as well a wire guage.

They work well. I have just a bit of over 40 years experience with lots of machinery, big small, inductive, resistive likely miles and miles of high, medium and low voltage wiring. I never teach or allow replacement of unit assemblies without testing to confirm why it is failing. Just trying to understand in this situation how to diagnose and I think the answer is there is none, the wiring wears out - just install new if your relays aren’t lasting. The IR stuff is supposed to help be somewhat predictive and fairly non invasive in lieu of measurements with a meter. Regular measurement techniques work on other stuff for these (kilns) - I don’t know there is a clear answer. Lots and lots of very old wiring, kilns and machinery, that are still working as designed. My guess, it is a real thing with some Skutt equipment and maybe just adds enough heat to the cabinet to cause issues. In other words the wire is known to wear out. If they simply wear out, the IR solution likely would be the same as for motors. Measurement of temperature above ambient or the trend of measurements above ambient over time could provide reasonable confidence in prediction. Interesting to note in the picture above, the loose connection is adding heat to the wiring, noticeable on both sides of the relay. The fix here is new connector or tighten the connection -all the heat goes away. This is a very common failure. Her picture shows melting within the relay but very good looking connections, not even discolored, pointing to a relay contact issue or overloaded contacts for reasons unknown.

Not doubting that especially if the old connections are failing and heating things or the wire is heating the cabinet because its resistance is rising. Gaining. more resistance will not burnout relays it actually decreases the current through the contacts. Just trying to understand how to test for this.

Any definitive evidence what caused the early relay failure?

For me I would initially be interested in the following: a context picture of your control board showing the connections to it , maybe from about two to three feet away so we can see the connections and the wires leading away a context picture of the element connections showing them and the wire that leads to the relays post the element resistance if you can measure them, if not can someone measure them for you so you can post here? So top elements measured resistance =______ ohms, middle section measured resistance = ____ ohms, bottom section measured resistance = ______ ohms. post a picture of the thermocouple itself and the wires leading to where it connects and tell us why you believe it is a type S If you hit the little + quote below this message and post the items named above it will be a direct response to this message

The specs on it say it will go to very low negative temps (-200 f or lower) so it’s likely the yellow and red are switched at the probe. The plug is polarized so most likely backwards at the thermocouple, small possibility someone wired the jack backwards

Yes, this is a good thought. I was just often in the situation to get asked and then I was in a bit of a dilemma. I guess I would say one’s perception is affected by experience. Any studio I walk in ………any ……….. home or commercial I see kilns have been under insulated for so long that we have surely wasted mega watts of energy globally. Reduction firing, let’s generate more CO! Wood firing, not sure anyone can argue anything environmentally good about that. Glazes that waste natural resources, soda firing, mining products….. The list goes on with respect to sustainability and outright environmental damage. I had a colleague point out oil is renewable, just not in our scale of time. She is right, but not a reason to keep improving what we do. I think the best one can do is encourage others, lead by example don’t let it get to you. Remember we are always learning so the things everyone thought were key yesterday may change a bit tomorrow. My food pyramid flipped upside down I think. Why isn’t it mandatory to plant X number of trees every time one wood fires? Just kidding, it’s just a suggestion that I think might make sense rather than try and stop all wood firing.

It’s been so long, the only thing I remember is the aggravating pinholes and premixed glazes that were ridiculously thick on occasion. What I do remember is we always fired to cone 6 which in the end seemed a bit hot for some of the Amaco glazes especially adding a soak. Their published firing schedule is a fast ending segment of 270 degrees per hour in the lasts 200 degrees putting them at Orton cone 5-1/2 to cone 6. Most of our kilns fully loaded could not achieve that speed at the very top end so even more frustration. Good or bad It drove us to learn more about glazes and abandon all the commercial stuff.

Just an add I have entertained this theory and I think he wanted to call it “packed bed porosity” as I recall. A nice theory that may have value, but I have never been able to confirm with confidence in several trials.

Interesting, my first experience with pinholes in glazes were with those very glazes, I believe. So much so that I decided to learn a bit about glazes. Mark has found a solution for his, so definitely test that. What I can share is some glazes will actually pinhole more the hotter you make them. For these compositions, the drop and hold firing schedule seems effective. Digital fire has a decent bit about this. For glazes affected this way a common thought is by composition their fired surface tension does not allow the pinholes to heal. For those, dropping temperature a bit allowing them to thicken slightly and holding allows the glaze to flow back together and heal the pinholes. My first experience with oatmeal was super frustrating with top end soaks and holds which for that glaze / clay combination made things worse. If a top end soak or hold seems to make things worse then I suggest reading about and trying (testing) a drop and hold schedule to see if that works for you.

Good catch & bad math interesting, does this fire 30 cy on and 30 cy off at 100% output?

Yes I believe they will be just fine. They are zero crossing so the fastest they can be commanded off or on will need to wait for zero crossing. I think the default for typical heating controllers would be approximately 200 milliseconds ( so 2 seconds, something on that order). The default typical fastest for kiln relays (if my memory serves) approximately 10 seconds. Measuring the amperage of a resistance load by ct ought to be fine especially at maximum output. I think your idea is fine and reveals the heated resistance as well, I am a sequential troubleshooter so any data with integrity is helpful to me. Not everyone troubleshoots in the same way though. aTo your other point about duty cycles, yes …….. and the controller generally is set to compensate or even things out using the top or bottom element to help the middle. That the kiln actually stalls is very interesting to me. It has potentially symptoms of several faults, yet everything has tested good. My take, I need to know some real values, thermocouple type, wiring sequence ….. something is wrong but without real confirmation I cannot speculate.

Without pictures, real measurements, response to all that’s been asked above, I think this will be difficult to solve.

Other trick that comes to mind for spraying. Spray even coat, gently pull the trigger 1/2 way (air only) and gently dry what you just sprayed. Future coats same procedure building up the thickness and drying each until it’s thickness is similar to a freshly dipped pot. Usually two to four even light coats. Dry each coat in between before applying the next. This works well over heavily underglazed areas on bisque ware as well and ensures each layer is applied evenly. Heavy underglaze often changes the absorbency locally so drying these areas before the next coat makes applying glazes evenly a snap. Definitely waster slabs under reglazed pots is good practice. Spraying allows for multiple even coats and is similar to preheating. You are trying to speed up the drying process in both cases.