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Bill Kielb

Solid State Relay Conversion

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Here is something that may interest you, within a month or so I will do a full SSR conversion with lid switch etc... for safety. This will further allow the use of some cheap bonded nitride shelves in these kilns. I believe I will extend the element useability by approximately 25 firings and have to guess at the energy savings from the shelves which are probably half the weight. 

Any speculation on savings? You may have experienced this already.

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Definitely interested in seeing how this works out. I assume you have a controller that will calculate firing costs, and you have a current baseline to compare to? I've always wondered just how much the SSR's can affect element life. Everyone says they do, but I've never seen actual numbers.

As for the shelves, I'm hoping they don't have a huge effect, because I don't want to buy new shelves! Think it would be worth it to do a firing without any pots, only shelves, and see how they differ? I have a feeling it won't be that big a difference per firing, but when you math it out for a year it could be a decent savings if you fire a lot. I think that for most people it will take years to recoup the added cost of fancy shelves.

This will be a very informative experiment!

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Agreed but the spark to the whole thing has been a fully powered, new set of elements in the cone arts (you are familiar with) just make (time wise)  the cone fire schedule,  So fast glaze, about six hours or less. Under heavy load (kiln full) and a default relay cycle time of 14s this time moves up to 7 - 9 hours because ............. loading and the cycle time of the relays prevent the elements from being on long enough to maintane the  firing speed.  So at the upper end of the firing by the time the relays fire a second time the kiln has actually started to lose  significant heating rate. As the elements wear, with the  default relay cycle time of 14s,, the firing times creep up until the controller errors at 14 hours.  Usually after 150 to 200 mixed firings on a set of elements.

Setting the relay cycle time to 10s (minimum)  improves this but is tougher on the relays ... but does decrease the standby losses by an hour to several hours.

The heavily loaded kiln has a significant effect on the timing but about 30 - 50% of the mass of a heavily  loaded kiln is probably shelves. So it may turn out to be quite a significant improvement. The time to cool should decrease significantly as well so from a throughput  perspective their firing cycles currently are 30 hours minimum for the smaller kilns but could likely decrease to 24 hours for a fast glaze firing. At that point I  likely would need to activate the downfire  segment option for all cone fires so users could dial In a slower cool down.

lots of interesting possibilities, not sure how it will work out actually. My guess  at least 10% or more in energy reduction, no kiln wash or extensive shelf cleaning and no more relay changes.

Edited by Bill Kielb

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This is an interesting topic from which I hope to learn something new. I'm familiar with the Advancer shelves, we have them for our 2 gas kilns at school. (But there where we have foundation money to pay for them, money is no consideration...) However, the notion of savings from SSRs is new to me, so please help feed my hungry brain. I can see how an SSR could cycle faster than the standard electromechanical ones, but how is this controlled? Is there a hidden option in my Bartlett controller for this?

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@Dick White

Yes there is.

If you refer to the technical manual the cycle time should be set to match your kiln. The default from Bartlet is 14 seconds between two relay turn on occurrences. It can be lowered  as low as 10 seconds for mechanical relays but that is it’s minimum dwell time.  When programmed for SSR the cycle time is change to zero which results in a 2 second  repeat application time.

A safety issue has always plagued electric kilns and the use of the bonded nitride shelves. Like carbide, they conduct electricity so in the event of a stuck relay the elements could be powered when the kiln appeared off. The conductive shelves increase the potential for electric shock in  the event they are touching an element.

SSR’s don’t fail often but can fail closed as well as open so their use in electric kilns has been a bit limited. As a way around this, most of the upper end kiln designs include a lid switch and interlock it to the controller error output so whenever the lid is open or the controller is in error, main power to the relays is  turned off mechanically.

Following  this safety  protocol makes using the bonded nitride shelves again safer in electric kilns for those working around them. Actually mechanical relays fail closed sometimes as well so the protocol actual improves the safety of the kiln regardless of shelves.

anyway, having measured and observed the operation of our kilns, it appears there will be a significant reduction in energy, no more relay changes and much less labor cleaning shelves and kiln washing.

 

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18 minutes ago, oldlady said:

OK, enough.   what is SSR?

Sorry solid state relay. They are now in the 30 - 50 usd range as opposed to a 20 - 30 usd mechanical relay that probably lasts 200 - 300 firings before it needs replacement.

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Solid state relay. A relay is an electrically controlled switch. A low voltage  current from the digital controller causes a heavy duty switch to close and turn on the elements. When the controller determines the elements have been on long enough, the low voltage current stops and a spring clicks the switch open. That is the loud clicking during the firing. A solid state relay replaces the the spring and mechanical contacts with electronic semiconductors. Silent, reliable, long-lived, and more expensive.

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I cannot comment on the SSR as I do not have a controlled kiln

But as to the Advancers you will find less back issues with loaders and a much easier load in and out-and more work coming out of same space. as the space savings will addd up .As to any energy savings well my guess is it pretty small in a small electric kiln.

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2 hours ago, Bill Kielb said:

Sorry solid state relay. They are now in the 30 - 50 usd range as opposed to a 20 - 30 usd mechanical relay that probably lasts 200 - 300 firings before it needs replacement.

If you shop around, you can get mechanical relays for $9-12. The last set on my L&L e18T-3 lasted almost 700 firings. There is a lot of variability in relay life, though. A lot depends on the design of the kiln and how well they are kept cool.

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1 minute ago, oldlady said:

thanks, guys.  you might want to put that in the title for future searches.

I've never seen someone refer to an SSR as anything but SSR, but if you search for solid state relay, the posts here explaining it will still show up

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26 minutes ago, liambesaw said:

I've never seen someone refer to an SSR as anything but SSR, but if you search for solid state relay, the posts here explaining it will still show up

Does that mean it won't be changed to be perfectly clear to all, even we uninitiated?

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2 minutes ago, Rae Reich said:

Does that mean it won't be changed to be perfectly clear to all, even we uninitiated?

Didn't say that. Just saying for search purposes that it shows up under solid state relay ;)

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Just now, liambesaw said:

Didn't say that. Just saying for search purposes that it shows up under solid state relay ;)

Unless it's in an index, how would I know that solid state relay is SSR? Or vice versa? Just askin'

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4 hours ago, Bill Kielb said:

Maybe, but mass is everything in energy required so I would say at least 30% of the total mass in many firings consists of shelves. Especially old heavy ones

But the difference in mass between a small kiln load of Advancers and mullite? Not 30%??

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5 hours ago, Dick White said:

Solid state relay. A relay is an electrically controlled switch. A low voltage  current from the digital controller causes a heavy duty switch to close and turn on the elements. When the controller determines the elements have been on long enough, the low voltage current stops and a spring clicks the switch open. That is the loud clicking during the firing. A solid state relay replaces the the spring and mechanical contacts with electronic semiconductors. Silent, reliable, long-lived, and more expensive.

But without the loud clicking, how will I know it's working?!... Hehe

Prior to reading this topic, I had only heard of "Solid State" when it referred to computer hard drives.  Interesting though.

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Let's look at 23"x27" round kilns, the most popular size electric kiln in the US- Skutt 1027, L&L E23T, etc. According to all the online sellers, a 20" full round Corelite shelf weighs 9.3 pounds. A 20" full round Advancer shelf weighs 10 pounds. For the making it easy, let's say they weigh the same. So if we're just going off of the mass of the shelf, there should be no savings in firing costs by using Advancers. Corelite are 5/8" thick, Advancers are 5/16" thick, for a difference of 5/16" per shelf. In a typical load you're going to use 5 shelves, so  total savings of about 1.5 inches per load. You can get a bunch of spoon rests or small plates into that space, so you basically get a free firing every 17 loads due to the space savings. The Corelite costs $55 per shelf, the Advancer is $260 per shelf, for a difference of $205 per shelf. If you take the cost of firing in my kiln, which is about $18 per load, it'll take more than 11 free firings to recoup the cost of each shelf. So 5 shelves, $18 savings every 17 loads, it'll take 935 firings to recoup the cost of the shelves. For the average hobbyist that fires twice a month, that's just under 39 years. For someone like me that would fire a kiln that size about 90 times a year, I'll recoup the costs in a little over 10 years. If I knock over and break a shelf during that period, I'm losing money.

These numbers get better if you start looking at rectangular shelves, where the Corelite shelves are heavier and thicker, and the Advancer shelves are cheaper. In a taller kiln, like a gas kiln with 48"+ height, the space savings become more apparent. And with 'knockoff' Advancers that cost less the numbers get even better. But for the typical round kiln, you have to fire a lot to make it worthwhile.

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thank you, neil.   i will stop envying the owners of the new kiln down around the corner with all its advancer shelves.   appreciate all this info even if i do not understand all the electrical components.  glad you are on the forums.

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@Rae Reich @Dick White

All right  as promised - the numbers and ciphering are complete using the advanced scientific method of a scale,  some actual shelves and actual hurricane student ware. I saw Neil's quote and I am guessing his math is fine. As a studio we don't own core light shelves and have stayed away from them because of the kiln wash issue and all the grinding that we do, plus flipping them over would require removing the wash so the numbers below are for our standard 3/4" solid shelves of which we have many and are very economical to purchase actually. But ….. it looks like the core light shelves are the same mass as the bonded nitride below so they would have the same or similar thermal effect as the nitride.

It Looks like we budget to buy about $2500.00 per year of new conventional shelves plus furniture and I would have to tally the expense of the Lees kiln wash since we were tired of kiln wash in our glazes and  of course there is diamond grinding bits for the removal of the ever artistic flowing student glazes. Oh not to be forgotten  the free volunteer time it takes to clean stacks of shelves every single week.

Will it save our backs - yes. Will it save hours of shelf cleaning and kiln wash - yes. And will it save energy and time to fire while extending the life of our elements - stay tuned, we are not sure.  

So the early speculation: 10% - maybe as much as 20% reduced heating load on the kilns. Why heat shelves if you don't have to, they look the same fired to a perfect cone 6 - Boring!

The incentive: Change the current mechanical relays to Solid State, likely no more relay changes, a safer studio kiln, longer element life, shorter firings (More throughput) and the ability to use nitride bonded shelves in them since the new safety has been added. So does the use of lighter shelves save energy and about how much is the question?

Just the shelves

  • Standard 3/4"  21" round half shelf in the studio = a touch under 10 pounds (we have a bunch)
  • Standard .394" (Economy) Bonded Nitride 21" half round = a touch under 5 pounds ( we have tried them and they are a dream to clean)
  • Weight of pots (Student) I can fit on a typical 21" half round shelf = Generally maximum under 6 pounds
  •  Can I fit more in the kiln with the approximate 1/2" height I gain from the thinner shelves - not really relevant in community fired kiln(s)

 

  • The rough percentage mass reduction I can expect with lighter shelves - Just under 50 %
  • The rough percentage the shelf mass is in relation to the pots on them - Somewhere between 40 - 50%, lets use 40% to be conservative
  • Percentage of shelf mass I will not have to heat 40% X 50% 0r 0.4 X 0.5 = 0.20 or our Magic number 20%

Kind of what we thought actually so our initial approximations were reasonable. Now as to the whys of this project, it is mainly the solid state relay which will improve firing, extend element life etc.... The latent benefit in a studio environment are mainly maintenance and inconvenience which is critical in an all volunteer environment of 55 resident artists.

Thats it, those are the numbers as promised!

Is this good for a home studio? not sure. If I put dollars and cents to this can I create a suitable payback period, likely not. I could say the same for an automatic controller upgrade though, heck we could all still be using cone sitters, they work fine. As a DIY by someone capable for the studio It looks like a one time cost of well under $300.00 per kiln to retrofit (Solid State Relay). I think for this studio it looks like a winner.

 

Edited by Bill Kielb

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@Bill Kielb Why are you avoiding CoreLite shelves because of grinding? They're no different than regular cordierite shelves in that aspect. Silicon carbide is definitely easier for grinding, though. Also, I've got 500+ firings on some of my Corelite shelves and have never flipped them. They're still as straight as the day I bought them. I think the thinner silicon carbide shelves will definitely be a savings over standard heavy cordierite shelves.

Another thing to look at for reducing firing costs is the firing schedule. I worked at cone 8 for a couple of years, and found that firing to cone 6 with a 40 minute hold to reach cone 8, instead of firing all the way up to cone 8, increased my element life by about 30%. I don't know if that 2 cone savings translates across all cones, but it may be worth trying. I will add that I tried it at cone 4 with a hold to 6, and the required hold time was much longer, and man of my glazes did not like it. A couple didn't even melt completely. Some glazes need the heat, not just the heat work. But if cone 5 holding to 6 could increase element life 10%, that would be great. Some day I'll find the time to test it. Unfortunately, it takes going through a full set of elements to find out.

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