Elinelin wrote:I work at EK Miller Co. in Portland. We build FuseStar kilns, which have the cooling system Bert described-- and there are quite a few of our kilns in use in the area, and also in the bay area. I think it works great-- cool air is never actually being introduced into the kiln, but heat is being removed quickly. The elements are wound on the outside of the quartz. There are also venting chimneys on the roof of the bell, if you need to crash cool the glass surface.
I'm not an expert, but I have some experience, and I have a few answers for you--
1) You do not need three-phase power to have quartz elements.
2) 12" might be too low for some things, but you can build up a brick wall to increase the height-- Just don't skimp on power if you want that flexibility.
3)A multi-zone controller can be a very nice luxury, but it should not be necessary-- you'll be able to tell if the heat is uneven.
4) Mercury relays tend to be more reliable, but solid state ones work well too.
5)I strongly reccommend a movable bell. Once you have your pieces carefully laid out, the last thing you want is for your table to hit a bump while you roll it into place.-- You always have the option of building a second table later.
I have also used Glasslam, and have always had success with it-- even on contoured surfaces. I hate gluing! But it seems to work.
Anyway, good luck with the kiln
I was talking with the engineer at Duralite about the open quartz tube design. He saw no reason not to use the same design but with the elements wound inside the quartz tubes.
I use an element design that uses nichrome wire in straight lines, not coiled. It is much less expensive to make than quartz tubes and coiled Kanthal. I am thinking however about retrofitting my kiln with a set of empty quartz tubes to do the heat exhaust thing.
I would think that using a multi zone controller to activate a relay that activates a fan at the point where the kiln is cooling slower than the program, would be a good idea.
I plan on using SSR relays on our next kiln building project. They cost less than mercury and are considered much better. Click click relays wear out pretty fast especially relative to SSR's which are electronic and if installed properly (not on the kiln, but on a nearby wall) they will last long and do a good job.
I would choose SCR relays if I had the choice. They are more sophisticated than SSR's, but require a 4 - 20 milliamp signal to activate them. At present The Bartlett Controller does not support this output. IT does support a signal that will run the SSR.