Mr. Mark thanks for your concern about my kiln project. 
What concerns the PID controller, not only brand defines the price, but its features also. The more advanced models enable PC connection to configure the controller and monitor the heating process. Other options are several levels of ramp control.
The wire holder concept is widely and successfully used for decades in infrared heaters and industrial applications. I have used it in my home made enameling kiln, it worked well but was designed for temperatures below 650°C (or 1200°F). The wire holders were not in grooves but placed vertically in a cylindrical chamber.
Yesterday night when I was milling the grooves I was also worrying about the heat escape from the wire between the ceramic and the brick. I have made the grooves even more open to the chamber inside.
Having the heating wire coiled on the wire holders I de facto do not need the groves, but I have decided to keep them to prevent that one element heats the neighboring ones.
My decision the use the wire holders was not quite voluntary. The reason for the problem is the small = low power kiln and 240 V grid. The total length of the heating wire is 20 meters. The length of the minimally stretched heating element is some 3 meters and I am not able to accommodate this length into the walls of the small chamber. (For 120 V the stretched element would be much shorter.)
I am not sure that it will work well, I only hope it will. At this stage there is no way back for me.
Thanks for your support.
Jan
What concerns the PID controller, not only brand defines the price, but its features also. The more advanced models enable PC connection to configure the controller and monitor the heating process. Other options are several levels of ramp control.
The wire holder concept is widely and successfully used for decades in infrared heaters and industrial applications. I have used it in my home made enameling kiln, it worked well but was designed for temperatures below 650°C (or 1200°F). The wire holders were not in grooves but placed vertically in a cylindrical chamber.
Yesterday night when I was milling the grooves I was also worrying about the heat escape from the wire between the ceramic and the brick. I have made the grooves even more open to the chamber inside.
Having the heating wire coiled on the wire holders I de facto do not need the groves, but I have decided to keep them to prevent that one element heats the neighboring ones.
My decision the use the wire holders was not quite voluntary. The reason for the problem is the small = low power kiln and 240 V grid. The total length of the heating wire is 20 meters. The length of the minimally stretched heating element is some 3 meters and I am not able to accommodate this length into the walls of the small chamber. (For 120 V the stretched element would be much shorter.)
I am not sure that it will work well, I only hope it will. At this stage there is no way back for me.
Thanks for your support.
Jan