neilestrick

Today I threw the bodies and necks for some tall bottles. I really enjoy assembling these. The bodies are 3lbs of clay, 12" tall. The necks only require 1lb since they're so narrow. I'll lose about 3" to shrinkage, so the finished pots will be just under 18".
 

Today I threw the bodies and necks for some tall bottles. I really enjoy assembling these. The bodies are 3lbs of clay, 12" tall. The necks only require 1lb since they're so narrow. I'll lose about 3" to shrinkage, so the finished pots will be just under 18".
 

Today I threw the bodies and necks for some tall bottles. I really enjoy assembling these. The bodies are 3lbs of clay, 12" tall. The necks only require 1lb since they're so narrow. I'll lose about 3" to shrinkage, so the finished pots will be just under 18".
 

Today I threw the bodies and necks for some tall bottles. I really enjoy assembling these. The bodies are 3lbs of clay, 12" tall. The necks only require 1lb since they're so narrow. I'll lose about 3" to shrinkage, so the finished pots will be just under 18".
 

Today I threw the bodies and necks for some tall bottles. I really enjoy assembling these. The bodies are 3lbs of clay, 12" tall. The necks only require 1lb since they're so narrow. I'll lose about 3" to shrinkage, so the finished pots will be just under 18".
 

Trimming the openings in salt pigs. Think it takes me longer to try and get the holes cut more or less evenly and round than it takes to throw them.

I'd use porcelain. The lower the absorption rate the better.

I was trained on a large gas kiln and never used electric until a few years ago. Having occasional opportunities to get into community wood firings and raku firing, I'm a happy camper. I finally got  OK with the fact that as much as I loved making my own clay bodies and glazes, and was pretty good at it, my situation just doesn't accommodate that today.  So I am using commercial bodies and glazes and find I like them just fine. I did a head-adjustment on myself to get out from under the old tendency to think gas/wood was superior to electric and that not mixing your own stuff is sort of a petty crime. Now I'm working to get Ok with limited throwing facility and getting into an appreciation of the conceptual and process aspects of hand-building.
My workbench today has a thrown and altered bowl form, then hand-worked with stamped, paddled, & incised techniques. I like how much work actually goes into making something look "other-than" a properly, nicely, thrown bowl.  
 

Running conduit under the house today, WHAT A CHORE.  24 inches of clearance and I'm a big 220lb 6'2" monster so not a whole lot of room to work.  Hopefully this pays off in the next few weeks and I'll be firing an electric kiln!!!
Wire arrives via UPS sometime next week and I can run the wire and call the inspector if everything goes swell.  Fingers crossed I did everything OK, it looks good anyway.

I have been out of touch with pottery for a very long time. Just getting back into it, a lot to try and remember but this is my first project I'm working on.

Drill bits are less likely to crack the piece, since they remove material as they make the hole. Hole cutters force the clay to expand to make room for the wall thickness of the cutter. If the clay is too firm, or the hole is too close to an edge, it will crack.
The biggest problem with all holes, and one that many, many people do not address, is the sharpness of the edge of the hole. Rubbing out the edge with a sponge or finger takes forever. The simplest solution I've learned is to use a countersink LIKE THIS ONE. Just twist it lightly in the hole once it's just past leather hard, and it will knock off the sharp edge. I use this on all my colanders, and I can do all the holes in a matter of a minute. It puts a nice little bevel that looks rounded once it's glazed.

Thank you. I've never used one of those, so I wasn't sure how it was powered.
To clean up the box:
1. Replace the power cord with a 6ga 3 wire cord. You can reuse the plug, just get a new cord. I buy the SEOW cords from McMaster, about $35 for a 10ft length. They're super flexible and easy to work with. Use a cord grip, or just a simple clamping cable connector to hold the cord securely in the hole in the box. Use a snap-in plastic grommet to hold the TC wire, and another for the controller power supply. You'll have to figure out which sizes you need for each cable. They not only protect the cord from the sharp edge of the hole, but keep the cord from pulling out if you accidentally snag it.
2. You can go with the single leg SSR if you add in a mechanical main relay. Every kiln system I've seen uses a definite purpose contactor (DPST-NO) for the main. Because it is big and your controller has low voltage output, you'll need an intermediate relay (pilot relay) between the controller and contactor. So for the pilot relay you'll need something that has a coil that will work with your controller, either single or double pole. L&L uses their standard 25 amp 2 pole 12VDC coil relays for the pilot. In the Skutt KM-1 external controller, they use a small single pole relay and just run the power for the other side of the coil directly off the main power. I've attached a wiring diagram of the KM-1 which should give you a good idea of how you can do yours. Either way works. The contactor, then,  will need a 240 volt coil. You'll have to set up your programming to turn the main relay on and keep it on when the kiln is firing, and off if there are any error situations, or at the end of the firing. The most important error would be to shut it down if the temp is climbing too quickly, which would indicate a stuck relay or TC issue.
3. Make sure you ground the box.
4. If this was my project, I would use a larger box so it's easy to work in, put in a terminal strip where the main power comes in, and distribute everything as needed from there. It'll make the wiring much simpler to deal with, and easier to see what's going on. Terminal connections are much easier and cleaner than wire nuts.
I think we're all on the same page here. You've got the thing working, which was the hard part (congrats!), now it just needs cleanup and safety concerns addressed, which is mostly just busy work. It's a great project.
@liambesaw I had a small test kiln last year that got really hot during firings. Because the kiln and box were only about 10 inches tall, there wasn't enough draft created in the box to keep it cool like it would in a taller kiln. The controller was getting very close to its max operating temp. So I installed a little computer fan in the bottom of the box, and it made a huge difference. I agree with @Bill Kielb that it would be good to avoid adding in more parts, but it will definitely work if it comes to that.
I've also attached a pic of a Skutt with SSRs. You can see the big cooling fins on the box.

Drill bits are less likely to crack the piece, since they remove material as they make the hole. Hole cutters force the clay to expand to make room for the wall thickness of the cutter. If the clay is too firm, or the hole is too close to an edge, it will crack.
The biggest problem with all holes, and one that many, many people do not address, is the sharpness of the edge of the hole. Rubbing out the edge with a sponge or finger takes forever. The simplest solution I've learned is to use a countersink LIKE THIS ONE. Just twist it lightly in the hole once it's just past leather hard, and it will knock off the sharp edge. I use this on all my colanders, and I can do all the holes in a matter of a minute. It puts a nice little bevel that looks rounded once it's glazed.

Drill bits are less likely to crack the piece, since they remove material as they make the hole. Hole cutters force the clay to expand to make room for the wall thickness of the cutter. If the clay is too firm, or the hole is too close to an edge, it will crack.
The biggest problem with all holes, and one that many, many people do not address, is the sharpness of the edge of the hole. Rubbing out the edge with a sponge or finger takes forever. The simplest solution I've learned is to use a countersink LIKE THIS ONE. Just twist it lightly in the hole once it's just past leather hard, and it will knock off the sharp edge. I use this on all my colanders, and I can do all the holes in a matter of a minute. It puts a nice little bevel that looks rounded once it's glazed.

I agree that this is a great thread. No denying that seeing someone build their own controller is very cool. But I do have a responsibility as a moderator to point out things that could be dangerous to others who would copy what's being done here (it's actually in the rules), and for the safety of the person posting. I don't know when a member isn't aware of the safety issues, or is just working through it fully aware that the final product will be done differently. Either way, I think it's good for things to be discussed, for the education and safety and knowledge of everyone involved. I don't think any of it diminishes the value and hard work of what's being done. In fact, I feel like to adds to the project, because it fleshes it out more. As I said before, I wasn't aware of the parallel feeder method, so I have learned something, too.
So on that note,  I have seen the charts for chassis wiring, and I don't think what you have there qualifies, because those cords are power wires, not chassis wires. Chassis wires are very short single wires connecting parts within the appliance, which are not bundled and therefore can dissipate heat well. What you've got there are power transmission wires, which require a much larger gauge and can be bundled. The chart that Liam posted is a good one to go by. If you look at all the wire gauges recommended by the kiln companies, they go with the 60C column because it doesn't hurt to be on the conservative side.
The danger of using them as a parallel system is that if any of the wires in a bundle comes loose, the others will be overloaded and overheat. There are a lot of rules about how parallel systems must be installed because of that, and they're limited to use in very high amperage systems where it's impractical to use large single wires. It's a code thing, not a personal preference. The fact that they're not overheating means that they are, in fact, performing as a parallel system should, but that doesn't mean it's safe.
The prototype Skutt SSR kiln I saw had a big heat baffle mounted to the front of the control box just like yours.  And their control box was mounted on the kiln. So it seems you're definitely on the right track there.
You don't necessarily have to have a fuse in the system, since it's under 50 amps. Once you get over 50 amps you have to have branch fusing in the system. It's another reason production kilns are more expensive than hobby kilns of the same size. More parts, more engineering.  Definitely have a fuse on the controller path, but you don't have to have one on the power path. If you do decide to put one in, size it with the breaker.
I would put in a mechanical safety relay to kill the whole system in the event of an SSR fusing 'on'.

Thank you. I've never used one of those, so I wasn't sure how it was powered.
To clean up the box:
1. Replace the power cord with a 6ga 3 wire cord. You can reuse the plug, just get a new cord. I buy the SEOW cords from McMaster, about $35 for a 10ft length. They're super flexible and easy to work with. Use a cord grip, or just a simple clamping cable connector to hold the cord securely in the hole in the box. Use a snap-in plastic grommet to hold the TC wire, and another for the controller power supply. You'll have to figure out which sizes you need for each cable. They not only protect the cord from the sharp edge of the hole, but keep the cord from pulling out if you accidentally snag it.
2. You can go with the single leg SSR if you add in a mechanical main relay. Every kiln system I've seen uses a definite purpose contactor (DPST-NO) for the main. Because it is big and your controller has low voltage output, you'll need an intermediate relay (pilot relay) between the controller and contactor. So for the pilot relay you'll need something that has a coil that will work with your controller, either single or double pole. L&L uses their standard 25 amp 2 pole 12VDC coil relays for the pilot. In the Skutt KM-1 external controller, they use a small single pole relay and just run the power for the other side of the coil directly off the main power. I've attached a wiring diagram of the KM-1 which should give you a good idea of how you can do yours. Either way works. The contactor, then,  will need a 240 volt coil. You'll have to set up your programming to turn the main relay on and keep it on when the kiln is firing, and off if there are any error situations, or at the end of the firing. The most important error would be to shut it down if the temp is climbing too quickly, which would indicate a stuck relay or TC issue.
3. Make sure you ground the box.
4. If this was my project, I would use a larger box so it's easy to work in, put in a terminal strip where the main power comes in, and distribute everything as needed from there. It'll make the wiring much simpler to deal with, and easier to see what's going on. Terminal connections are much easier and cleaner than wire nuts.
I think we're all on the same page here. You've got the thing working, which was the hard part (congrats!), now it just needs cleanup and safety concerns addressed, which is mostly just busy work. It's a great project.
@liambesaw I had a small test kiln last year that got really hot during firings. Because the kiln and box were only about 10 inches tall, there wasn't enough draft created in the box to keep it cool like it would in a taller kiln. The controller was getting very close to its max operating temp. So I installed a little computer fan in the bottom of the box, and it made a huge difference. I agree with @Bill Kielb that it would be good to avoid adding in more parts, but it will definitely work if it comes to that.
I've also attached a pic of a Skutt with SSRs. You can see the big cooling fins on the box.

I agree that this is a great thread. No denying that seeing someone build their own controller is very cool. But I do have a responsibility as a moderator to point out things that could be dangerous to others who would copy what's being done here (it's actually in the rules), and for the safety of the person posting. I don't know when a member isn't aware of the safety issues, or is just working through it fully aware that the final product will be done differently. Either way, I think it's good for things to be discussed, for the education and safety and knowledge of everyone involved. I don't think any of it diminishes the value and hard work of what's being done. In fact, I feel like to adds to the project, because it fleshes it out more. As I said before, I wasn't aware of the parallel feeder method, so I have learned something, too.
So on that note,  I have seen the charts for chassis wiring, and I don't think what you have there qualifies, because those cords are power wires, not chassis wires. Chassis wires are very short single wires connecting parts within the appliance, which are not bundled and therefore can dissipate heat well. What you've got there are power transmission wires, which require a much larger gauge and can be bundled. The chart that Liam posted is a good one to go by. If you look at all the wire gauges recommended by the kiln companies, they go with the 60C column because it doesn't hurt to be on the conservative side.
The danger of using them as a parallel system is that if any of the wires in a bundle comes loose, the others will be overloaded and overheat. There are a lot of rules about how parallel systems must be installed because of that, and they're limited to use in very high amperage systems where it's impractical to use large single wires. It's a code thing, not a personal preference. The fact that they're not overheating means that they are, in fact, performing as a parallel system should, but that doesn't mean it's safe.
The prototype Skutt SSR kiln I saw had a big heat baffle mounted to the front of the control box just like yours.  And their control box was mounted on the kiln. So it seems you're definitely on the right track there.
You don't necessarily have to have a fuse in the system, since it's under 50 amps. Once you get over 50 amps you have to have branch fusing in the system. It's another reason production kilns are more expensive than hobby kilns of the same size. More parts, more engineering.  Definitely have a fuse on the controller path, but you don't have to have one on the power path. If you do decide to put one in, size it with the breaker.
I would put in a mechanical safety relay to kill the whole system in the event of an SSR fusing 'on'.

Drill bits are less likely to crack the piece, since they remove material as they make the hole. Hole cutters force the clay to expand to make room for the wall thickness of the cutter. If the clay is too firm, or the hole is too close to an edge, it will crack.
The biggest problem with all holes, and one that many, many people do not address, is the sharpness of the edge of the hole. Rubbing out the edge with a sponge or finger takes forever. The simplest solution I've learned is to use a countersink LIKE THIS ONE. Just twist it lightly in the hole once it's just past leather hard, and it will knock off the sharp edge. I use this on all my colanders, and I can do all the holes in a matter of a minute. It puts a nice little bevel that looks rounded once it's glazed.

Drill bits are less likely to crack the piece, since they remove material as they make the hole. Hole cutters force the clay to expand to make room for the wall thickness of the cutter. If the clay is too firm, or the hole is too close to an edge, it will crack.
The biggest problem with all holes, and one that many, many people do not address, is the sharpness of the edge of the hole. Rubbing out the edge with a sponge or finger takes forever. The simplest solution I've learned is to use a countersink LIKE THIS ONE. Just twist it lightly in the hole once it's just past leather hard, and it will knock off the sharp edge. I use this on all my colanders, and I can do all the holes in a matter of a minute. It puts a nice little bevel that looks rounded once it's glazed.

I ran into a kiln like that once, where the previous repair guy had put a Bartlett controller on a Nabertherm and didn't do it right. I got a nice little shock when I tried to push an element in, even though the controller wasn't actually running. Luckily the teacher at the school had never gotten shocked. This is why two pole relays are used. Switching only one leg, the element won't heat up because the circuit loop isn't closed, but when you touch the element and ground it out you'll get hit.
@jbruce I'm also worried about the extension cord wires. Those wires are only rated for 12-20 amps, depending on the size of the cord. How did you arrive at it being large enough for 4 times the 40 amps? And if the kiln pulls 40 amps, the wires should be rated for 50 amps, which means you should have 6 gauge wire in there.

Drill bits are less likely to crack the piece, since they remove material as they make the hole. Hole cutters force the clay to expand to make room for the wall thickness of the cutter. If the clay is too firm, or the hole is too close to an edge, it will crack.
The biggest problem with all holes, and one that many, many people do not address, is the sharpness of the edge of the hole. Rubbing out the edge with a sponge or finger takes forever. The simplest solution I've learned is to use a countersink LIKE THIS ONE. Just twist it lightly in the hole once it's just past leather hard, and it will knock off the sharp edge. I use this on all my colanders, and I can do all the holes in a matter of a minute. It puts a nice little bevel that looks rounded once it's glazed.

Drill bits are less likely to crack the piece, since they remove material as they make the hole. Hole cutters force the clay to expand to make room for the wall thickness of the cutter. If the clay is too firm, or the hole is too close to an edge, it will crack.
The biggest problem with all holes, and one that many, many people do not address, is the sharpness of the edge of the hole. Rubbing out the edge with a sponge or finger takes forever. The simplest solution I've learned is to use a countersink LIKE THIS ONE. Just twist it lightly in the hole once it's just past leather hard, and it will knock off the sharp edge. I use this on all my colanders, and I can do all the holes in a matter of a minute. It puts a nice little bevel that looks rounded once it's glazed.

Drill bits are less likely to crack the piece, since they remove material as they make the hole. Hole cutters force the clay to expand to make room for the wall thickness of the cutter. If the clay is too firm, or the hole is too close to an edge, it will crack.
The biggest problem with all holes, and one that many, many people do not address, is the sharpness of the edge of the hole. Rubbing out the edge with a sponge or finger takes forever. The simplest solution I've learned is to use a countersink LIKE THIS ONE. Just twist it lightly in the hole once it's just past leather hard, and it will knock off the sharp edge. I use this on all my colanders, and I can do all the holes in a matter of a minute. It puts a nice little bevel that looks rounded once it's glazed.

That's a handy tip, thanks @neilestrick

Drill bits are less likely to crack the piece, since they remove material as they make the hole. Hole cutters force the clay to expand to make room for the wall thickness of the cutter. If the clay is too firm, or the hole is too close to an edge, it will crack.
The biggest problem with all holes, and one that many, many people do not address, is the sharpness of the edge of the hole. Rubbing out the edge with a sponge or finger takes forever. The simplest solution I've learned is to use a countersink LIKE THIS ONE. Just twist it lightly in the hole once it's just past leather hard, and it will knock off the sharp edge. I use this on all my colanders, and I can do all the holes in a matter of a minute. It puts a nice little bevel that looks rounded once it's glazed.