Potters & Sculptors - Making Rock from Mud
Our kiln elements last about one year, actually 163 firings.
This consisted of:
63 ___ ^6 firings and;
100 __ firings at ^04 or less.
Most of the ^6 firings have a six hour controlled cooling between 1800 F and 1500 F.
This assumes everyone at the studio recorded their firings in our Kiln Log.
Our kiln is a Cress E23 220 Volt 36 Amp (on a 50 amp circuit and outlet).
The 8.6 kw output potential s a tremendous amount of heat for a 3.3 cu/ft kiln.
Of course the elements cycle on and off because neither the power relays nor the ceramic pieces could tolerate the kiln elements being in an on position for very long.
Interesting discussion. I had not considered the effects of firing upward using 9999 but I've never done that, only fired part way down at 9999. Good info to know for the future.
My home kiln is a Skutt 1027 and so far I've fired it 224 times and have not had to change the elements or relays, only the thermocouple a couple times. The kilns where I work are Skutt 1227 and the elements, relays and thermocouples need changing much more often although I don't know at how many firings as I'm the only who wants to keep records. I wonder if elements etc need changing more often there because perhaps some of the glazes spit and the overall conditions of a community setting where more gets packed into a kiln than ideally fits, less frequent vacuuming, etc.
If your kiln controller can be reset for a platinum thermocouple, we have found that to be a good investment. It's accurate to just a few degrees and lasts far longer.
I'll mention that to our tech guy next time we need a repair and ask about a platinum thermocouple.
I'm reading with interest about the use of SSR, it has never come up before in my small realm that many potters work in. I don't get out much. Could someone here go into a little more detail about setting them up and their use. What cycles them during preheat, is there a heat sensor involved. Do you use one for each existing switch or one for all of them, I see people talking about using them and adding them as each switch burns out. We have 4 kilns going, 3 different sizes, so do you need multiple SSR's. Sounds interesting.
Solid State Relays work the same way mechanical relays do. The control system, a microprocessor in our kiln, turns on a low control voltage which causes the SSR to turn on the high voltage. I have no idea what they might cost or if they're compatible with a Bartlett controller. But you would definitely need one for each current relay in order to control the kiln in the same way.
Some SSRs are volumetric like an amplifier, so would definitely not be compatible with a Bartlett controller. A controller for a volumetric SSR would have to create variable voltage outputs rather than an off and on.
Being involved in ceramics as long as you have I'm sure you recall some older kilns used mercury switch relays, which probably never needed replacement.
We bought replacement Tyco relays for $19 online, the same ones our kiln manufacturer sells for $48, which is probably the most economical route.
SSR's need to be sized to the circuit in your kiln. They take the place of a relay, so you would need the total wattage of your kiln & divide it by the number of circuits(or look on your kiln spec sheet). I believe they recommend that the SSR be rated at 125% of what the circuit would pull. An SSR is cycling in milliseconds so that it appears as a constant level either going up or down depending on what the TC is telling the controller to do. They do produce heat as a byproduct of their function so they need to be cooled with finned heat sinks or small fans. I run a small muffin fan on top of my controller anyway to pull cool air up through it to keep the board cool. They gain their efficiency by not cycling on & off like a switch, but more like a dimmer so that they only pass through the current needed to heat the kiln at that moment. I am no expert by any means, just sharing what I know. There are others on here with way more knowledge than I possess. jhp