paulcook Posted October 31, 2023 Report Share Posted October 31, 2023 I recently installed a PID controller on an old Skutt 145. It was (is?) working well, but I had something odd happen on my third firing. About 5 hours into the firing, at 500C, I needed to open the kiln to move stuff around. I opened up the kiln removed my mold, did some stuff and put it back in about 5 minutes later. Kiln top was open the whole time. Closed the lid and came back 10 minutes later. The temperature was going back up very slowly, and plateaued around 425C. I noticed that the two bottom elements were not glowing, only the top one. The top element is connected to one SSR, and the two bottom elements to a separate SSR. I noticed that one of the relays was not as hot as usual (feeling through the enclosure) while the other seemed to be normal temperature. I am assuming one of the SSRs overheated and triggered the switch to fail open? The bottom elements never came back on during the firing. The next day I plugged the kiln in and went up to 500 no problem at all. All elements glowing and running off the PID. I did push in any elements that weren't neatly in their grooves, but doubt that is what solved. Any thoughts? Quote Link to comment Share on other sites More sharing options...
neilestrick Posted October 31, 2023 Report Share Posted October 31, 2023 Did you leave the kiln on while your were moving the stuff inside? Sounds like maybe the SSR has a built-in thermal management switch and it got too hot? Do you have heat sinks and/or a cooling fan on the SSR's? You should. If it's a wall mount box then you can probably get by with just heat sinks. If it's mounted close to the kiln I would install a cooling fan. Quote Link to comment Share on other sites More sharing options...
paulcook Posted October 31, 2023 Author Report Share Posted October 31, 2023 Yea the kiln was on with the lid open for about 5 minutes. Is that bad? My concern was the elements got damaged, but they glow again now. The SSRs are mounted on heatsinks in a steel enclosure. Not much venting to be fair (just gapped the lid on the enclosure about 1/16 using washers). Control box is not mounted to the kiln. Glad to see that you don't think the elements are the problem. Quote Link to comment Share on other sites More sharing options...
neilestrick Posted October 31, 2023 Report Share Posted October 31, 2023 I would explore venting the enclosure better. A small computer case fan is super cheap and will do a great job of keeping things cooled off. Opening the kiln at 500C is not great for any kiln furniture you may have in there- shelves, posts, etc. They're pretty tough but not really made for extreme thermal shock resistance. Keeping the elements on while in there is an electrocution hazard for you. European kilns have a lid switch to prevent that. paulcook 1 Quote Link to comment Share on other sites More sharing options...
Hulk Posted November 1, 2023 Report Share Posted November 1, 2023 (edited) Adding fans, reminds me of a solution we used for a P100 (a computer, new circa 1994; it'd been in continuous service for fourteen years) on a production line in the Steel Mill. The fan in the power supply had failed; upon opening the box, we found a rather thick layer of glittering dust (dirt, dust, insect bits, and metal particles) on everything. After blowing it out and replacing the power supply, we circled back to add an input fan (blowing in*), fitted it with a filter, and made a calendar item to check/clean the filter in six months. It was still chugging away when I left the Mill. There was a bit of yelling about it - the Sheet Division Manager wanted to know what IS THIS!? Who's behind this joke and it ISN'T FUNNY!! All heads turned to Murf, heh, oh we had a good laugh on that one! *where the input fan blows harder/more than the power supply's fan, the inside of the box stays much cleaner. We used a simple and inexpensive motorcycle carburetor foam sock style filter, easy to mount, easy to clean. Edited November 1, 2023 by Hulk It's a motorcycle/small engine aftermarket filter thing paulcook 1 Quote Link to comment Share on other sites More sharing options...
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