Dick White

So, what we are saying here is that the weak point in the circuit is the breaker which can only handle 80% rated capacity if fully loaded for more than 3 hours. Thus, a 60 amp breaker for a 48 amp continuous load. The wiring in the rest of the circuit is all 6 ga (or better) to match the 60 amp breaker, including the kiln power cord, even though only 48 amps will pass. The only exception is the inch and a half or so of the prongs of the 6-50 plug and receptacle. Are they truly limited in their capacity to pass no more than 50 nominal amps, or is the plug and receptacle more about the NEMA configuration to prevent end-user mix and match stupidity?

We'd rather keep you in the group to talk about your pottery than see you living in a motel fighting with the insurance company after a fire.

It is true that 48 amp kilns are built with 50 amp plugs/receptacles on 60 amp circuits. So, yes, a kiln drawing less than 30 amps could use a 30 amp plug on a 40 amp circuit. But this kiln is likely pulling more than 30 amps (though we don't actually know, just doing the math from factory spec sheets), so the 30 amp plug is insufficient.

Still assuming that the elements are the ones specified for the original configuration, 2 things are possible: 1) The elements are sufficiently worn now that they are pulling less than the specified amperage, and that would get it slightly below the 30 amp breaker. But when the elements are completely worn and replaced, it would be above the breaker size. 2) Breakers are designed to carry only 80% of the rated load for long periods of time, hence the 125% rule for continuous loads of 3 hours or more. The 30 amp breaker likely did not trip because it wasn't overloaded for long enough, but it probably would have in the middle of a firing.

And didn't have a fire? Or at least toasted wires?

There are a number of inconsistencies here. The now-2-section kiln, if still containing the proper elements from when it was a 3-section kiln (which we don't know), would be pulling 31 amps (which is insufficient for the volume of the kiln and will have unbalanced heating, but that's not our problem; it's only our problem when our tax dollars are spent on a fire department call...). Under the 125% rule (which the electrician may or may not be aware of, some are, some aren't until pointed to that page in the code book), that would require a circuit of 38 amps, or rounding up to the next available breaker size, 40, which the picture shows was used and is correct. The plug and receptacle shown in the pictures is a standard 30 amp set. The power cord shown in the picture appears to be the original cord but with the original 50 amp plug cut off and replaced by a 30 amp dryer plug from the hardware store. That alone is insufficient for the kiln (and I can't imagine how the previous owner ran the whole kiln on that...). In the N. American electrical inventory, there is a 40 amp breaker, but there is no standard 40 amp plug and receptacle; it skips from 30 to 50 amps. Thus, the plug needs to be a 50 amp (6-50) set while the breaker and wiring would be 40 amp material (including the black cable coming in from the left that goes back to the main panel, which in N. American standard cable colors is 8 ga., suitable for 40 amps) . Let's just assume the electrician also properly used 40 amp wire inside the metal flex cable in that installation, but set an insufficient 30 amp receptacle to avoid having to repair the existing power cord's currently insufficient plug? Just too many unknowns.

Several concerns about the current state of affairs - you took out the bottom section, which changes the amperage draw from 48 amps to 31 amps, assuming the elements are the correct ones for a 240V 1027 kiln. That requires a 40 amp circuit, including the associated wiring. You said you were using a dryer circuit, which is typically a 30 amp circuit. You say the electrician changed the circuit breaker. Changed it to what amperage? If the sparky put the required 40 amp breaker on an existing 30 amp circuit, you need a new sparky and hope your homeowner's insurance is paid up. Regarding the kiln itself, the design of Skutt kilns places hotter elements in the top and bottom rows to compensate for heat losses through the lid and base. The middle 4 rows of elements are cooler because less heat is need in the middle compared to the top and bottom. By removing the bottom section, you have eliminated that one element at the bottom that needs to be hotter. It may have somwhat unbalanced heating now. Furthermore, though it is now the size of a 1018 kiln, kilns are designed with optimal ratios of heat to kiln surface area. The standard 1018 kiln needs 39 amps to perform up to maximum expectations. Yours now has only 31 amps. Thus, you will probably be limited to cone 6 at best.

Firing to 1240 and holding for 30 minutes is probably going to be same amount of heatwork as going 10 more to 1250 and shutting down.

The flame test is the best way to see if there is a good draw or too much. The board in the window is fine, no need to make a hole in the wall if you don't have to. One other consideration with kiln vents is providing sufficient make-up air from outside the garage. The fan system will create negative pressure in the space as well as in the kiln, so fresh air needs to come into the garage from somewhere, such as an open window or door or other vent. A complicating issue is the source of the make-up air (the door or window) needs to be some distance away (or around the corner) from the kiln vent exhaust. If the source of the make-up air is near the exhaust, the negative pressure in the garage will suck the stinkies right back inside It will be a vicious circle. Having the source of the make-up air at some distance from the exhaust will allow the stinkies to dissipate before fresh air is pulled into to replace the air that was exhausted.

Have you considered standard camera tripods with added cellphone holders that screw on to the tripod in the manner of old time cameras?

Alice, definitely going to get Bailey's clone of the Advancer shelves. Several hundred less list price, and we have a set of them for one of the gas kilns at school, they are just as good as the real Advancers we have for the other gas kiln. I will call them tomorrow to see what kind of price he can quote for the 4 kilns. It would be awesome to do one PO for the whole lot.

Update, and thanks for all the suggestions and insights. We won. Sorta, we hope. They have agreed to consider approving purchase orders for the 4 kilns. Some minor grit in the gears is recent price increases since I first submitted the proposal, but hopefully they will continue forward. One other "change" is instead of asking for the upgrade to the quad elements in the two e28s, I am going to shoot the moon and ask for Advancer shelves instead of the standard furniture kits. Wish me luck, and thanks again. dw

Thanks Bill and Neil, part of our context is physical space and part is electrical and part is political. The 4 kilns are crammed into a modest closet room with barely enough space to walk between them. The room is well vented, so that's not a problem. The electrical setup is odd. There are 2 circuits to the room - one side of the room has a 208v single phase 60 amp circuit (for the e23 kilns), the other side has a 208v 3phase 50 amp circuit for the (e28 kilns, though the Skutts only needed 40). Each side has a transfer switch to shift the single circuit to either plug. Thus, we can only run one of each type of kiln at a time, one firing while the other cools and is reloaded. Yes, it's odd and cumbersome, but that's what is there and they've made a point of saying that will not change. I considered the quad elements, but those would exceed the available electric. Interestingly, the eq28 is 14,950 watts while the straight e28 is 14,340 watts; a mere 600 watts difference, but the quad would require 60 amps, a nonstarter, while the straight fits in the existing 50 amps. The only thing the electrician will need to do is remove the inline 3 phase contactors needed for the manual Skutts. And yes, Genesis controllers! Do you know if L&L now installs the current sensor standard as Skutt does? And yes, Bill, I am with you on all of that. But HQ doesn't think that way. They can't see the kilns (and the students can barely see them) and don't have to use them. They can see the swimming pool, the weight machines in the fitness room, and the tennis courts and baseball fields. Those things are obvious when they are in disrepair and get fixed (or in the case of the weight machines, replaced as soon as they are seen as at a competitive disadvantage to those at Gold's Gym or LA Fitness, lest we lose customers). The kilns - as long as I can keep them propped up, there is no capital budget or plan for timely replacement. The only paid employees are those in direct paying customer contact, i.e., the teachers (of which I am one). All indirect operations are done by volunteers who are "paid" in kind with free access to the facility (but limited, lest it become taxable income as a fringe benefit - yes, the IRS took issue with letting the volunteer golf course attendants play for free) . Thanks again for your wise insights. dw

This is a question for the hive mind here, in anticipation of needing to negotiate with TPTB up the hill. The direct question - what is the typical life expectancy of a kiln? The TL;DR back story - I am the more-or-less manager of a pottery program in a community recreation center operated by the county government. We have 4 well-loved (not particularly) manual kilns, two 20-year old L&L J230s that are used exclusively for bisque and two 15-year old Skutt 1227s that are used exclusively for glaze. The Skutts are rated to cone 8, but are only fired to cone 6. The throughput of the student body results in each of the kilns being fired approximately 75-80 times per year. The hard element holders in the L&Ls have proven their worth, while the unprotected sides of the Skutts are, well, a hot mess given the loading and unloading is a) heavy clumsy shelves, and b) done by volunteers. The elements in the bisque kilns have not been changed in at least 5 years, maybe longer, I can't remember when I did them and don't feel like looking through the records. But, bisque being no big deal, the L&L elements are like the Timex watch ad, takes a beating and keeps on ticking. The Skutt glaze kilns are another story. We get around one year per set of elements, i.e. 70-80 cone 6 firings with cone 8 elements before a firing takes longer than the 20 hours available on the kiln sitter. Doing the math with the above facts, that is 15 element changes (after which the bricks now are so holy that the pins don't stay in) and at least 1,000 firings. There is a rumor around the building that for first time in decades HQ has some funding available for the most needy projects in the county park system, and I have proposed new kilns (L&L e23Ts for bisque and L&L e28Ts (208/3ph @ 14kw vs. 11kw in the current Skutts)). The question I am expecting from on high and don't have a ready answer - why are my brick kilns wearing out so soon, colonial brick houses (we are in Virginia, so there are a few of those around) last hundreds of years. What is a reasonable life expectancy for a non-production kiln used in a production environment as described above? Thanks, dw

Yup, 60 mesh vs. 600 mesh will do that.

I'm going to pop in here for 2 things, one old, the other new. First, back to the wifi issue. It may be that Neil is right (is he ever wrong?) about a defective board, but in some of my work with the Genesis controller, it may just be a weak wifi signal from the access point router being too far away. When I first installed them on my kilns in the garage, I got almost no signal out there because of 2 brick walls and 3 floors and interior walls in the way. An old saw in wifi-land is "3 walls and you are out" and a diagonal signal path through a wall or floor counts as 2. My solution, and one I have recommended to others, is put an inexpensive wifi extender/repeater somewhere in between to boost the signal through the last wall or farther distance to the kiln. Maybe that will help your kiln connect and then you can download the log files. Second, yes, as we all know (or as some don't fully understand) a slower ramp rate in the last 100C yields the cone bend at a lower temperature. Whether that lower temperature is achieved sooner on the clock or not, you'll have to do the math. Intuitively, I suspect that because it is running slower, it will take longer even though it doesn't have as far to go. And if the slowdown is being caused by challenged elements, the runup to that last 100C is probably going to be a lot slower too, so the whole firing will take a lot longer, not shorter. Anyway, it is also important to note that in the cone-fire mode, the controller is tracking the actual achieved ramp (vs. expected ramp) and adjusting the final cone temperature to account for a faster (to a higher temperature) or slower (to a lower temperature) ramp. That is not going to affect this discussion because Wayne is running a custom ramp-hold sequence to prescribed temperatures in each segment. For those, if the kiln cannot maintain the requested ramp rate for whatever reasons, the controller will keep chugging at the slower rate until it finally gets to the setpoint. That will mean, for an expected cone bend, it will be overfired.

The relay is probably broken, replace it.

No popcorn here. M'lady came in thinking it was time to scream at the football game on TV, and saw that the game was not on. So she screamed at me to turn the game on. But I already saw Neil's video on Clayflicks, and was watching again. Good show.

The problem with solubles in a glaze slurry is that the dissolved flux materials (e.g., borax, soda ash, sodium leaching out of neph sye or some frits) moves into the interior of the bisqued ceramic with the water as the glaze is applied. Then it stays there. Because it is a flux, the ceramic body is fluxed (and thus overmelts), not the glaze. It you want to use a soluble material in a glaze, you have to use the glaze right away, before it has a chance to fully dissolve into the water, or used it in a specific way, such as carbon trap shino, where the migration of the dissolved sodium creates the desired effect.

Can you post a picture of these dials and a picture of the electrical rating plate that will be somewhere on the side of the kiln or the control column. I doubt we will be able to find a manual, but we can probably help you figure out how it works.

FireMate is the trademark for a certain line of kilns made by Cress. The instruction manual can be downloaded here: https://cressmfg.wpenginepowered.com/wp-content/uploads/FX-INSTRUCTION-MANUAL-FOR-FX-KILNS.pdf

Can you share a link to this ceramic website that claims bat pins are unique to specific wheel brands. In the USA, all bat pins are fundamentally similar and often interchangeable. The basic pin is an industry standard 1/4x20 hex head cap screw, and the wingnut is the matching industry standard 1/4x20. The only wheel brand difference might be in the length of the pin. A Shimpo Whisper has the holes drilled through the thin areas of the wheel head, and so a 3/4" length is sufficient to go through with enough to put the wingnut on. A Brent wheel has the holes drilled through the radial reinforcing struts on the underside, and so needs a pin that is 1 1/4" long to have enough protruding to put the wingnut on (but only use 1 1/4" length - 1" is too short to go all the way through and 1 1/2" will hit the raised joint of the 2-piece splash pan). Other brands may have differing thickness of the wheel head where the hole is drilled. There is also a foolish body of thought out there that we don't need no steenkin' wingnuts, just stick the bat pin in the hole and if needed wrap a scrap of paper around it to wedge it in place so it doesn't wiggle (which it will). If you are having trouble with the wingnuts loosening over time from vibration, then one of the suggestions above by @Kelly In AK will keep the wingnut tight. NB - Go to your local orange or blue big box home store or your favorite hardware emporium and get some stainless steel ones. Those won't rust.

Be aware that most pottery clay bodies and glazes do not like extreme thermal shock. Don't put your your casserole into a preheated oven, rather put it in the cold oven and warm it up as the oven comes up to temperature. When cooked, don't put it right on a cold stone counter, it will crack from the temperature differential.

Another issue with sprayers of any type is that the powdered minerals and oxides in a glaze slurry are much more abrasive than paint, and so the tip of the sprayer will likely wear out. Be sure what ever you get has a ready source of replacement tips.

You need to contact Skutt for the exact dimensions of the brick and advice. Some manufacturers (e.g., L&L) kept the outside dimension of the metal band the same, but the inner dimension (and kiln volume) is smaller by 1" (1/2" on each side) for the extra thickness of the brick. Others (e.g., Skutt I believe, but their website no longer shows anything with 2 1/2" brick to make a comparison) kept the inner dimension (and kiln volume) the same by using a longer metal band for the thicker bricks. If my recollection is correct, new 3" bricks will not fit in the band designed for 2 1/2" bricks.