low fire SSR + APM upgrade?

[bayanMM]

Howdy y'all!

I run & maintain the kilns at a Minnesota-based designer tile factory, & I'm currently researching potential kiln upgrades for all of our equipment. We primarily run Skutt KM1227's / KM/1027's on a high frequency lowfire schedule; our 14 kilns are scheduled to fire almost every day that isn't a weekend or holiday. Most of our glaze firings are to ^06/05. We almost exclusively use lowfire hobby glazes, & have found that an army of smaller topload kilns gets more reliable results than much larger car kilns. 

We've just expanded to a second location in northern Minnesota, & we have plans in the books to expand to multiple locations out of state within the next 5 years, so I'm primarily interested in maintenance solutions that will reduce downtime. Our EM relays routinely fail around every 6-8 months, & elements around or just below the year-mark. I've been scrolling through these forums for a bit, & I found some discussion on solid state relay conversions that I found to be promising (I've reached out to Skutt about new boxes for SSR conversions for our existing kilns), & found some notes around the web on APM elements.  However, a lot of what I found pertained to folks that work in the mid-highfire ranges.

Cards on the table, budget is not an issue here, but I wanted to run this by y'all before I send in my proposal to the higher-ups. Will we see a noticeable/justifiable improvement in kiln performance/component service life with these upgrades?

 

[neilestrick]

@bayanMM So you're only getting 150 or so firings from a set of relays? That's not all that uncommon for Skutt kilns. Their control boxes tend to run a little hot, and heat is what kills relays. The cooler the control box, the longer they'll last. One of my kilns had a set of relays that went almost 700 firings.

SSR's will definitely last longer, but it's going to be an expensive upgrade for sure. SSR's will also improve element life, but I can't say just how much. I've never seen a test that shows how much better it actually is. Could be 5%, could be 25%. They won't improve the results from the firings in any way. As to whether or not they'll be worth the cost of upgrading, you'll have to math that out. I assume you're not buying the mechanical relays directly from Skutt? You can get them online for 1/3 of the cost, about $10 each. The SSR's themselves are pretty affordable for future replacement, but the up front cost of the box isn't going to be cheap.

A lower cost alternative for the kilns you already have is to install a simple $10 computer fan in the control box. You should get at least double, if not triple, the number of firings with the box staying cooler. Even if you can just get the relays to last 1 full year, and then change all the relays one day every year, whether they're dead or not, you'll have zero down time and now worries about them dying. Say you're paying $10 per relay, that's $420 a year for relays for all 14 kilns. A complete SSR box for each of those kilns is probably going go to cost $1000 or more (a regular box is $700), so let's say $14,000 to do them all. Divide that out by $420 and you get 33 years worth of mechanical relays. So the math doesn't work out in favor of SSR's unless you can also figure out if there are any real savings in firing costs or labor that may pay out over the life of the kiln. If the computer fan won't fit inside the box easily, mount it on the outside at the bottom of the box. It could blow through the existing louvers, or you can cut a hole for it to blow through. If you install another relay in the box you can hook the fan up to Output 4 on the controller so the kiln controller can control it, or just put a toggle switch on the box to manually turn it on and off, or just let it run 24/7.

APM elements are great unless you have issues with glaze splatter or things blowing up. When stuff lands on them they tend to fail, so you need to keep them clean. And according to the Skutt web site you won't see any benefit at low fire temps. The main benefit of APM elements is that they don't sag and warp like regular elements at high temps (cone 10). At low fire temps it's not as big of an issue. Instead, I would look into getting a beefier element. Skutt may be able to do that for you, or also talk to Euclids.com and see if they can help.

[Bill Kielb]

1 hour ago, bayanMM said:

We've just expanded to a second location in northern Minnesota, & we have plans in the books to expand to multiple locations out of state within the next 5 years, so I'm primarily interested in maintenance solutions that will reduce downtime. Our EM relays routinely fail around every 6-8 months, & elements around or just below the year-mark. I've been scrolling through these forums for a bit, & I found some discussion on solid state relay conversions that I found to be promising (I've reached out to Skutt about new boxes for SSR conversions for our existing kilns), & found some notes around the web on APM elements.  However, a lot of what I found pertained to folks that work in the mid-highfire ranges.

Cards on the table, budget is not an issue here, but I wanted to run this by y'all before I send in my proposal to the higher-ups. Will we see a noticeable/justifiable improvement in kiln performance/component service life with these upgrades?

My findings were all advantages. Tighter control, less wear on the elements, better maintenance of programmed firing rates and indirectly less energy as firing times were maintained rather than extended so the additional time of losses through the shell were reduced significantly.  If as you fire loads the fuller ones take more time than programmed then the kiln is marginally powered which for residential style pottery kilns is typical, especially cone six and above. Your experience here would be the best judge of whether this is significant for you in your situation.

Low fire is easier for sure, but the benefits remain even at lower temperatures. Our other finding in conjunction with this was could we integrate the SSR solution with lightweight bonded nitride shelves which are electrically conductive so could we make safe with SSRs. The bonded nitride were lighter, and averse to glaze damage, anyway the savings in firing mass was in the order of 30% or greater which translated to $$$$ per firing directly. It was another look at moving the kilns from a marginally powered state to a more adequately powered which indirectly extended the lifetime of the elements.

Our observation is most residential kilns are designed at about 110% so when elements wear by 10% it’s time for replacement. Doing everything above likely increases this to 115-120% so in a studio environment with five kilns maybe a worthwhile investment from maintenance, energy, and production.

I mention all this because you may actually see bigger benefits to this in your environment. Last note, keeping the SSRs as cool as possible is always worth it with respect to lifetime operation. External mount better than integral and lower better than higher for thermal gradient. Networking your kiln status likely could provide benefit as well and  some of the new touch screen controllers do this nicely now as well for a reasonable cost these days. I think a base Bartlett touch screen is on the order of 300-400 dollars now.

Hope that helps

[bayanMM]

Thank you both so much, this has all been really helpful for me, & has given me a lot more to work with. My takeaway is that SSR's or internal cooling may be the best/most immediate solution to streamlining our maintenance cycle, & different elements would be a bonus, but not the biggest fix, while doing both may yield the best long-term results. My pipedream is for our standard typeK thermocouples to be the only part we switch out within the year; right now we schedule replacements every 6 months or as needed. Unfortunately, thermocouples happen to be the only repair that regularly is preventative, rather than reactive.

 

@neilestrick Thanks for the tip on upsizing the elements vs APM's; my primary issue with our current equipment actually happens to be how quickly our elements sag/warp into really incredible conditions before arcing sometime around the 10-12 month mark. This actually has been more of a problem with our two large Olympic front-load electrics, so this may also be a solution for those two while we still have them around. I'll be writing Skutt & Euclid shortly to pick their brains about it & get estimates.

Would there be any concern about changes in firing characteristics with upsizing the elements? 

 

@Bill Kielb Your video on SSR's was super informative, & I'll be sure to forward it up with my proposal. We're currently in the process of networking all of our preexisting & future kilns; right now HQ only has one convert that we use as a general test kiln for new glazes, upgrades/hardware changes, & data tracking through KilnLink. Company furnished the second location with the new KMT models; as of now they have 8, with plans for 12 more within the year. Anyways, I've noticed from a month of data that there seems to be a trend for fuller loads (10-11 layers, 20-22 shelves in a KM1227 208 3p, 1.5in apart) to significantly lag behind shortloads, but I think I need more data & time to have that for sure. It never occurred to me that max density had that much of an impact on draw & relay health; we all figured it was as simple as more stuff = more time.

I saw a lot of discussion about electrical safety w/ bonded shelves; Advancers make up half of our shelving inventory. It wouldn't be too hard to have my crews kill each kiln @ the breaker as soon as they hit unloading temp, but I like the KISS idea of retrofitting SSR converts w/ a euro-style lid switch- I feel there's less room for catastrophic human error there. 

[neilestrick]

6 minutes ago, bayanMM said:

Would there be any concern about changes in firing characteristics with upsizing the elements? 

Shouldn't be any difference. The element wire would be thicker, but the resistance and amperage draw would be the same. If you're going to be buying a lot of new kilns, it would also be worth checking out other brands to see what they have to offer, as they may be able to increase the efficiency of the maintenance requirements. Paragon and L&L, for example, don't need pins to hold the elements in place, which make element changes much faster.

11 minutes ago, bayanMM said:

My pipedream is for our standard typeK thermocouples to be the only part we switch out within the year; right now we schedule replacements every 6 months or as needed.

Have you considered type S thermocouples? With the volume of thermocouples you go through, they might make sense financially.

13 minutes ago, bayanMM said:

but I like the KISS idea of retrofitting SSR converts w/ a euro-style lid switch- I feel there's less room for catastrophic human error there. 

This can be done with the mechanical relays, too. You do it through the control side by putting the switch on the neutral line between the controller and the relays. It's standard on all front loading L&L kilns.

[bayanMM]

1 hour ago, neilestrick said:

Shouldn't be any difference. The element wire would be thicker, but the resistance and amperage draw would be the same. If you're going to be buying a lot of new kilns, it would also be worth checking out other brands to see what they have to offer, as they may be able to increase the efficiency of the maintenance requirements. Paragon and L&L, for example, don't need pins to hold the elements in place, which make element changes much faster.

Have you considered type S thermocouples? With the volume of thermocouples you go through, they might make sense financially.

Very good to know, I'm starting to lean towards beefing up instead of grabbing APM's, but the price point will end up being the final deciding factor here towards thicker wire. Slowly switching over to L&L or ConeArt is actually my preferred long-game solution, & I have a whole other proposal written up for all that, but it's a long shot- this company has really serious brand loyalty to Skutt products (they also got really burned out, pun not intended, on a number of bad experiences w/ 3 large Olympic frontloaders that we're still dealing with), so it'll be a tough sell. Part upgrades is my compromise proposal to at the very least extend the maintenance cycles.

I briefly looked at type S, but the number of reports on their fragility compared to K is a bit of turnoff.

[neilestrick]

5 minutes ago, bayanMM said:

I briefly looked at type S, but the number of reports on their fragility compared to K is a bit of turnoff.

They are fragile, so you'll have to rely on your people being careful when loading and unloading the kilns. They'll last a really long time if you can avoid breaking them, though.

[Bill Kielb]

3 hours ago, bayanMM said:

I've noticed from a month of data that there seems to be a trend for fuller loads (10-11 layers, 20-22 shelves in a KM1227 208 3p, 1.5in apart) to significantly lag behind shortloads, but I think I need more data & time to have that for sure. It never occurred to me that max density had that much of an impact on draw & relay health; we all figured it was as simple as more stuff = more time.

Since you have data you should be able to confirm the run time extension for more load  so that additional run time means more shell losses. If your run times are noticeably extending then your kiln is not maintaining its firing rate for the larger load which means a bit underpowered for that load.   With respect to the load if the shelves are 30 - 50% or more of the load (by weight) then that much energy is being used to fire shelves which is non productive actually. You should be able to load two kilns similarly but use the thin nitride versus whatever old style and gather data for KW used in the firing to easily compare what this might be worth.

On schedule firings mean shorter run times compared to extended schedule firings which means more relay cycles and more energy used (the shell losses thing). We weighed the shelves and then the shelf filled with wares. It turned out the shelves ended up to be  30-50% of the firing load so changing to thinner and lighter shelves is often a pretty easy way to save energy as well as wear.

FWIW - Cone art is one of the brands that has used 2-1/2” brick plus 1” insulation which is significantly better than 3” of brick. ( at least 10% I believe) It just is flat out plain physics but I am not aware of another brand that offers additional insulation regularly unfortunately. 

last thought that may help, maybe not — heavier gauge elements are definitely sturdier but total element loading is based on surface area to a great degree. So the design compromise is usually how much element surface can we get in the kiln given current resistance per foot values which often establishes how long the element will last.

 

 

[Min]

 

Since you are firing so frequently I'ld factor in the time it takes for the kiln to cool also if/when you replace the kilns. I've owned electric kilns that had 2 1/2" walls, 3" walls, 2 1/2" plus 1"fibre and a couple that had 4 1/2" walls, noticeable difference in cooling times. An issue with having insulating boards is if/when you need to change a brick, dealing with the insulation adds to the job. Another factor is the thickness of the lid and the floor. Re ConeArt kilns, I don't know if they all do but the one I have has a section in the middle of the kiln with no elements. There is an element in the floor, 3 TC's, fires evenly but I'ld imagine that with tiles the element free section in the middle might be an issue depending on how close your shelves are loaded.

I'ld be wary of the energy savings claims, from Euclids: "Claims of realizing significant energy savings from a particular style of kiln construction should be questioned. Comparing a 2.5" brick kiln wall with and without 1" of backup board does give a calculated 32%* difference in heat loss, but this won't provide equivalent energy savings. This number is based on the kiln holding at temperature indefinitely, and it is only part of the equation. Heating up the kiln insulation also uses energy and additional insulation requires increased energy. For typical firings, the reduced heat loss is offset by the increased energy required to heat the kiln. 

*Calculated using Thermal Ceramics Heat Flow program"

For quite a few years we made our own elements, used 12 or 13 gauge wire, they definitely lasted longer than the standard gauges used. If you go this route make sure the channels in the bricks are large enough to accommodate the larger diameter elements or see if they can have them wound on a smaller mandrel. Saves messing the brick channels up more than usually happens with element changes.

[Bill Kielb]

1 hour ago, Min said:

Heating up the kiln insulation also uses energy and additional insulation requires increased energy. For typical firings, the reduced heat loss is offset by the increased energy required to heat the kiln. 

*Calculated using Thermal Ceramics Heat Flow program"

That’s an interesting interpretation as 1” of insulation has likely less mass or at best the same as 1/2” of firebrick plus a better R value as a result. Heat loss is generally better thought of as a steady state process over time as well.  I am guessing no one would recommend removing some of their home insulation because their furnace cycles and it takes energy to heat the mass of the insulation. 

So heating the extra brick (in a 3” case”) and the losses through the brick should be greater as well. I get the not 32% direct savings because the lid and bottom are not soft insulated (Which is why I used the 10% number) but did they publish actual results? Really really curious  what those results are at this point. I am sympathetic to it not being 32% so marketing hype of up to 32% more efficient annoys me but physics is physics, there will be a savings in losses and reduced thermal load compared to 3” brick which is known more efficient than 2-1/2”

Anyway ......... we just proved this anecdotally in one of these threads by suggesting someone wrap their homemade kiln which was very underpowered  in 1-2” fiber to which he tried and finally got his kiln to fire to temperature.

“For typical firings, the reduced heat loss is offset by the increased energy required to heat the kiln. “ this is interesting phraseology as we know the losses for a 3” kiln are significantly better than losses of a 2-1/2” kiln and a 3” kiln has more mass to heat,  so a 2-1/2” kiln with less mass and a higher R value performs worse?

I don’t know the  answer but I would love to see those results, I am not a fan of statements that can misrepresent in either direction actually.

When we do any thermal design, less mass lower conductivity and for high temperature, reduced radiation is a pretty straightforward thing without a lot of mystery. Ceramic kilns seem to fall into an interesting niche of mystery though.

Quick add here, I have emailed Euclids and asked them to forward their data.

[neilestrick]

I think there's definitely a reduction in heat loss with the use of fiber insulation behind the bricks, but I have never agreed with their claims of 30% savings for the same reasons Euclids has stated. The 30% number is based on heat loss while holding at temperature, not while heating up, the extra insulation is only applied to 55-75% of the kiln, and heat loss reduction does not necessarily translate directly to energy costs. We've had a lot of discussions here on the forum about this over the years, and I have yet to see a side by side comparison of extra-insulated vs traditional kilns and their actual energy costs when being fired with an equal load of work in them. I disagree with Euclids that it is a wash, though. There is some benefit, but most kiln companies have decided that it's not enough of a benefit that they want to build their kilns that way. Building a very efficient kiln is not difficult, but as efficiency increases a lot of other things get worse- durability, ease of shipping, ease of repair, safety, cost, etc. It's all about finding a middle ground with all of those factors, and why most kilns are constructed essentially the same. After fixing hundreds of kilns over the years, IMO the simpler the design the better.

The main reason that round top loading kilns are so popular is their simplicity. They're easy to build, easy to ship, easy to set up, and easy to repair. And that simplicity also makes them affordable to buy and to maintain. Front loading kilns are often built with added insulation because they are already much more complicated to build, ship, set up, and repair. Plus their design offers more protection of the fiber components.

I think that a big part of increasing efficiency is reducing the heat transmission between the bricks and the outer jacket. The metal is a big heat sink. I would love to see a comparison of 1" fiber vs 1/8" fiber behind bricks and how they affect firing costs. I'm betting the 1" is not 8x better than the 1/8".

The problem is that fiber products are fragile. Blanket, board, paper, whatever, none of them are durable. Sandwich them between bricks and a metal jacket and they compress and rub and wear out from the expansion and contraction of the bricks and metal. Every kiln with backup insulation that I've had to replace a brick on has been a nightmare. The backup insulation is a crumbly mess and a lung safety hazard. As a kiln owner, if I have to pay an extra 10% in electricity costs to make repairs easier and less costly and safer and increase productivity because of faster cooling times, I'm happy to do that. The cost is so low that it's easily offset by adding a couple of cents to the price of each pot. For a hobbyist who isn't on deadlines and whose kiln doesn't get as much abuse as a production kilns, the backup insulation is not going to be a problem, but if you're only firing once or twice a month there's also not going to be much of a cost benefit. I'm all for better efficiency and reducing energy costs, but I don't think there are enough pottery kilns in the world to make much of a dent there. I think investing in green energy sources would be a much better way to go about it.

[neilestrick]

11 hours ago, Bill Kielb said:

I am guessing no one would recommend removing some of their home insulation because their furnace cycles and it takes energy to heat the mass of the insulation. 

Houses are basically held at temperature, not heated up every day, so not an apples to apples comparison.

Imagine it's the dead of winter, 0F degrees outside, and you have two houses. One is insulated and one is not insulated, and neither one has the furnace turned on, so it's 0F degrees inside both houses. If you turn the furnaces on and heat the interior air temp from 0F to 70F in both houses, the amount of energy needed will not be all that different. The more powerful the furnaces, the less difference there will be. However maintaining 70F for the rest of the winter will take considerably more energy for the non-insulated house.

[Bill Kielb]

10 minutes ago, neilestrick said:

The 30% number is based on heat loss while holding at temperature, not while heating up, the extra insulation is only applied to 55-75% of the kiln, and heat loss reduction does not necessarily translate directly to energy costs.

I agree, the 30% number is marketing wank mostly because the whole kiln is not treated. A percentage is for all sake a percentage so whatever temperature we are speaking it’s the percentage so steady state or climbing is really a non issue unless we have a discussion of the specific performance of things at various temperatures which gets more complex. But then again we have the very same discussion with fire brick.

There are many choices of insulation, but I understand costs / margins are a killer. Simpler is better, but power steering and power brakes also took time to become standard so att some point kilns will need to evolve.

32% is just a loss improvement number so marketing but a wash in savings seems an even farther stretch so as they invited, I contacted them for more info. We will see. I really like Euclids and have suggested them on many occasions so hopefully what a I get from them is meaningful.

[Bill Kielb]

30 minutes ago, neilestrick said:

ouses are basically held at temperature, not heated up every day, so not an apples to apples comparison.

Houses vary in temperature by their firing differential and go from setback / setup to comfort temp. The definition of percentage is what it is. Kiln firing energy is taken as the whole process - no mystery really. Saving 10% at 100 degrees is less than 10% at 1000 degrees but in the process we must go through all points. I just don’t see a practical point there over the course of a firing except......... for less insulated  the firing takes longer and the user incurs more shell losses from a less insulated kiln. The equivalent  term in the bus. is standby losses.

[neilestrick]

29 minutes ago, Bill Kielb said:

Houses vary in temperature by their firing differential and go from setback / setup to comfort temp.

Same idea as I described above. Getting the room temp up to comfort levels requires little difference in energy use between an insulated vs non-insulated house. The difference comes in maintaining the temperature. In pottery kilns it's all about climbing, not holding.

52 minutes ago, Bill Kielb said:

Simpler is better, but power steering and power brakes also took time to become standard so att some point kilns will need to evolve.

Both of those solved a problem with performance (ease of use) and safety. Backup insulation is a bonus for those who find that option important, more akin to buying a hybrid vs gasoline car.

Kilns have already evolved. There are well insulated, durable kilns on the market, they're just not part of the round top loading kiln market. You have to decide what features are most important to you and what you can get for your budget, just like buying a car. If you want an all-electric SUV with a 350 mile range and all the latest safety features, you don't go looking at $25,000 vehicles. If you want a well insulated, front loading kiln with type S thermocouples and solid state relays, you don't look at $4,000 kilns.

[Bill Kielb]

19 hours ago, neilestrick said:

Same idea as I described above. Getting the room temp up to comfort levels requires little difference in energy use between an insulated vs non-insulated house. The difference comes in maintaining the temperature. In pottery kilns it's all about climbing, not holding.

Yeah, I do agree that kilns have gotten better, not so much that standard brakes  and power steering  were seen as a problem, just an easier way, but of course more costly. Same said for automatic transmissions, an improvement that took time. The topper would be power windows, can you get a car without one, or a keyfob. Same excuses: cost, too complicated etc....  when I compare  home kilns to industry practices ...........potters have the short end of the stick IMO. But I do get it, costs and margins are a thing, just me whining about how little potters get while consuming more energy and their budget to fire. Fortunately electric here is still very cheap. Having said all that they have evolved a bit. Not great, but a bit.

The house is still relevant but can be debated but mostly because of what steady state is deemed by some which is not really relevant since the process  and the percentage loss during the process is  relatively the same throughout. The argument gets esoteric when the R value changes as temperature increases, but  that is in large part due to the insulating medium or trapped air and its density change. Same argument for fire brick, the R values change as temperature goes up. This leads folks to claim, hey it’s 30% at 1000 degrees, not 32%!  A true statement, but we can say the same about the fire brick. As a whole process from start to finish, the loss percentage is consistent. As a measure of how much energy it takes ....... that varies from a minimum with small temperature differences to very large at the end of firing.

I don’t really see any energy argument in heating something from 0 to 2000. It has to be done every single time. so I can’t find a logical basis for arguing the less insulated house or kiln leaks less  throughout the process because it has to maintain or hold some magic temperature.

Maybe this is a clearer analogy: If we were talking about filling a leaky bucket then the bucket  that leaks more would take more water to fill. If we stop and hold it at points, it still leaks water, basically more water than if we didn’t stop and more water than if it had smaller leaks. In energy, time dependent rates suffer from higher losses the leakier they are because the time is extended. From a practical standpoint It doesn’t leak less because we are going slower or maintaining some level for a bit. The leak never stops.

I definitely could be wrong, but as of yet, I can find no compelling real argument.

[Min]

On 5/8/2021 at 10:34 AM, Bill Kielb said:

....but as of yet, I can find no compelling real argument.

Jeremy Willis (professional engineer) has been designing kilns since 1984 for Pottery Supply House / Euclids. He is a managing director of The Pottery Supply House and the manager of Euclid's Elements. Willis's predecessor, Eric Poschmann, has a brother who owns and operates a heat process technologies company by the name of Synergetic Technologies who does work for Pottery Supply House / Euclids. Synergetic has been around for 35 years. Given their decades of experience and qualifications, I would trust they know what they're talking about.

[Mark C.]

A bit off topic but still relevant . I'm working with Skutt on a rusty stainless issue (metal band testing -more later on this) but in talks mid winter Skutt  they said that all kilns for European Market requires a kiln paper between metal and brick. I'm testing this on a jacket replacement very soon-They shipped me the jackets just before having a bone removed from thimb. I'm just about well enough to tackle this job again. I ordered the thin Bullseye 1600 degree shelve paper used  in glass work and will install between bricks and metal jacket. Not the same as fiber but still a barrier. I'm using it to get more life from the metal jacket vs insulation .Its an easy fix and cheap and easy to install when rejacketing a kiln.Should make for vapor not affecting metal as bad.

Big beliver in 3 inch brick even for bisque temps myself aslo big fan of advancer shelves -they pay for themshelves in space and energy saved in production firing right away.

[Bill Kielb]

2 hours ago, Min said:

Jeremy Willis (professional engineer) has been designing kilns since 1984 for Pottery Supply House / Euclids. He is a managing director of The Pottery Supply House and the manager of Euclid's Elements. Willis's predecessor

Good to know!
I will expect an email response then, they did invite inquiry and I sent the email. Have about 40 years of involvement myself in a myriad of thermodynamic processes, it will be interesting to hear the explanation and the intent of the phraseology as well as see their data.

[bayanMM]

so quick update:

Regarding the elements, I got conflicting signals from Skutt vs Euclid; Skutt tech said that a lower gauge element retrofit wouldn't be possible, but advised the APM upgrade, while Euclid gave me a quote for a set that actually comes slightly cheaper than the stock elements before s&h. 99% on going with Euclid's lower gauge.

I'm going to push for the SSR's in my proposal; everything I'm seeing is pointing towards the increased longevity + efficiency being worth the money in the long run. I am curious about how the SSR's will affect the mid-late fire; data has been showing that the controller goes to full blast really early on dense loads (consistently around 600*F), & lags significantly behind the programmed ramp. We're actually in the process of ordering more KMT1227's for my location, so I'll see if I can get a factory SSR upgrade for one of those, & hold off on the others while we run tests to confirm that it's all worth it.

My plan is to individually test these upgrades on 4 KMT1227's: one stock, one w/ low gauge, one with SSR, & for a final round, one with both upgrades. I figure that the data from a handful of firings each should give us something concrete before next year. I'll be sure to share results as we get them, & will happily share what we have right now if y'all are interested.

Thank you all so much for sharing your collective knowledge & experience!

[Bill Kielb]

2 hours ago, bayanMM said:

data has been showing that the controller goes to full blast really early on dense loads (consistently around 600*F), & lags significantly behind the programmed ramp

If these are relay driven kilns, then there will be a maximum speed with which they are allowed to turn on. (Often something like 1 0 seconds between two activations) This can reduce the available power since they must cycle. If what I described proves true, then the SSR will reclaim a good bit of this power as they can activate much more quickly and will reclaim a good deal of off cycle time as heating time. If you always hear clicking throughout the firing (Especially when lagging), then the SSR’s will reclaim this time as useful heating energy. Additionally since you experience lag at such a low temperature and  if you can test run lighter shelves with about the same amount of wares, you would likely remove 20-40% of the heating load so I would definitely test and record. That’s energy you are just wasting and all your kilns running all year likely make this very worthwhile. Your savings would be the energy saved not heating all that mass and any shell losses as a result of the firing taking longer. So it could save significant energy in your case.

Just some thoughts

[neilestrick]

3 hours ago, bayanMM said:

Skutt tech said that a lower gauge element retrofit wouldn't be possible, but advised the APM upgrade

Kiln companies generally don't like to do anything that is out of spec. It prevents a lot of headaches for them from a tech service standpoint.

3 hours ago, bayanMM said:

We're actually in the process of ordering more KMT1227's for my location

If you really need to fire faster, then get a KMT1227-PK.  They have a lot more power than the regular 1227, are rated to cone 10 instead of cone 8. Skutt could just make different elements for the 3 phase models that would allow them to get to cone 10, but instead they make you upgrade to the PK version.

 

[neilestrick]

1 hour ago, Bill Kielb said:

If what I described proves true, then the SSR will reclaim a good bit of this power as they can activate much more quickly and will reclaim a good deal of off cycle time as heating time.

Not entirely related, but his past weekend one of my students sent me the data log from a recent cone 6 firing on their kiln with standard mechanical relays, and I compared it to the logs from my SSR kiln. Both kilns are L&L, rated to cone 10, with zone control. I saw a couple of interesting things:

1. Their kiln could keep up with a 400F/hr ramp up to 1970F. Mine can only go about 325F/hr. I don't think it is a power issue or relay issue, though. My student's kiln only has two sections, whereas mine has 3. Their 2 relays run at pretty much the same percentage throughout the entire firing. In my kiln, the top and bottom relays run about the same, but the middle runs at 30-40% less than the other sections. The kiln isn't able to use the middle section to its full potential without overheating the other sections, so the firing slows down. It doesn't slow down so much that it's really an issue, it's just an interesting difference.

2. Both kilns track the traveling set point the same (on a ramp it can keep up with). There doesn't seem to be any accuracy differences between the mechanical relays and SSR's. I thought the SSR's would track it more closely because of the shorter cycling time, but they don't.

There was remarkably little difference between the two logs. Just looking at them you wouldn't know which had which relays. The difference will be in element life and probably cost, but in terms of firing speed, accuracy, etc there doesn't seem to be any difference between the two types of relays.

[Bill Kielb]

1 hour ago, neilestrick said:

There was remarkably little difference between the two logs.

I think it makes sense until the kiln cannot provide enough energy to track. When I ran into a kiln whose elements were well worn if the relay delay was set in the 15 to 20 range and to get a must have firing or two out of the existing elements I would drop the delay back to minimum (10 seconds).

Funny, all of a sudden things were fine and I had to convince the owner, no you really need elements and this will decrease your relay life. For a kiln that keeps up, the delay is not a power limit so the control should track just fine. really load the kiln though and that cycle time might limit the amount of power needed to track. Reducing that cycle time also had the benefit of evening zones out, it was amazing to watch especially at the top end. It also became difficult to convince the owner to please buy new elements, this will not last forever!

Last funny story, I have used the old element repair trick by just intertwining or overlap the two ends of a broken element (a few inches) and saying, this might only last one firing if you are lucky. A week and several firings later they hadn’t gotten new ones yet because the repair was working so well! Yikes! Stopped doing that for people.

[neilestrick]

8 hours ago, Bill Kielb said:

I have used the old element repair trick by just intertwining or overlap the two ends of a broken element (a few inches) and saying, this might only last one firing if you are lucky.

I've had the same experience with that. I've had some that fried the first firing, some that lasted months. I don't even try any more because the risk of it failing at a bad point in the firing.