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Hey yall! I recently was given a kiln, the Cress E-23. I have never fired my own work prior to this time, opting to drop it off at a studio because I did not have the wiring for a personal kiln. I ran a successful bisque fire for the first time, and am wanting to do a glaze test this week. What is a good schedule for a cone 10 firing? Is it important to cool slowly? What knowledge can you share? The schedules I have found (though scarce) are like this SEG1 100/hr to 220 with a 1 hour hold SEG2 300/hr to 2300 with no hold SEG3 108/hr to 2361 with a 1 hour hold
The facility in which I am working is currently awaiting the prolonged install of a replacement gas reduction kiln. In the meantime they have been firing cone 10 oxidation in a Paragon Viking 28, single phase, with a max temp of 2350F. It is hard wired to what I've been told is the appropriate amperage. When I was brought on board the kiln was failing to reach cone 10 and giving the FTL (Fired Too Long) code. At that juncture when we opened up the switch box the top segment of elements were slightly brown, we tightened the brass bits and the pigtails, all the elements were testing okay, as well as the relays. We fired the kiln with a load of only furniture and it reached temperature. So we fired it again, it didn't reach temperature and displayed the FAIL code. Replaced the thermocouple, and opted for a Type S model because it is rated for porcelain and stoneware temperatures. Reset the controller to the Type S model. Fired the kiln twice and FTL'd on the second firing, then replaced all the elements. The kiln fired perfectly to cone 10 for the next 7 firings. The alarm sounded at around 2100F on the 8th firing even though the alarm was maxed out and set to 9999. We hit enter on the kiln, stopped the alarm, the firing continued but did not reach temperature according the guard cones, but didn't give an error message. After it was unloaded the temperature was giving sporadic readings. Checked the wire connections, then tested the controller with a paper clip and it gave a room temperature reading. Opened the switch box and discovered that a fuse had blown. Replaced the fuse and the kiln fired perfectly for another 4 firings. On the 5th firing the alarm sounded around 2100F again, pressed enter, continued to fire and it failed to reach temperature. Turned the kiln off to run tests and check wire connections which everything appeared to be okay. Turned the power back on and now is showing TC2- (code for a failed thermocouple in the center two terminals of a multi-zone kiln, although can appear in a single zone kiln apparently) . The thermocouple is only 6 months old and has been through less than 15 firings. I have personally loaded and unloaded 90% of the firings since the thermocouple was replaced and I am highly cautious about staying clear of the thermocouple. I know that it is a very fragile thermocouple. It ultimately could be broken. Replacement has been ordered and its on its way. We are in the midst of an extremely busy term, with high volume, glaze ware is stacking up and I have a deep seated fear that the thermocouple may not fix the ongoing problems. If a mercury relay goes out can the kiln still run? Is there another major component of this model of kiln that could be perpetuating the alarm sounding, under-firing, causing a fuse to blow, ruining a fairly new thermocouple? What could have caused the wires connecting to the elements to brown? Could their be a connection between the browning of those wires and a bigger issue? I'm at a complete loss, and would like to get some preemptive feedback in case the thermocouple does not fix the issue, or the errors persist even once the thermocouple is in place. ~Worried Clay Worker -M. Williams