paulcook

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.

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?

@neilestrick Totally the reason - smart man!

Wired this up over the weekend - it works! Only took it up to about 200F, but gets to temp and maintains well. Was bummed to find out that it is not programmable, but don't know what I expected for $25 (with thermocouple and SSR included!). Max temperature is also a bit of a question mark at this point (the documentation is not very good). But I believe it is 1300C or (oddly) 1999F. I did replace the thermocouple with a Skutt brand. Also, made it remote / not mounted to the Kiln and that was great advice from Neil. Nice to not have to worry about how hot it's getting in the box.

@neilestrick Those Orton boxes are very cool! I'm going to (perhaps foolishly) proceed with my plan. I can't justify putting $600+ of equipment on a 40 year old $450 kiln. I'll report back on how it goes. The kiln is for firing investment plaster. It will only be used by me, maybe 5-6 times/year, supervised, with fire extinguisher nearby In a studio environment, I wholeheartedly agree that a DIY solution is not ideal. Really appreciate everyone's insight and help!

Is there a controller with a 14-30 receptacle that would be compatible with my kiln? The Genesis Mini and others do not seem like they are plug-and-play?

PS - I was planning on lining the outside back face of the control box with ceramic fiber insulation and mounting the box about 1" off the kiln (thickness of the insulation).

Thank you Neil and Bill. I will be building out the control box separate from the box already on the kiln. It will, in essence, be what you described Neil, with conduit connecting the boxes. I will be adding physical switches to each element. I won't add the relays, but will add in-line fuses to each hot. And will still use cones Bill. BOM is about $200 of parts - all-in. I can't justify $600+ on a purpose built kiln controller (that will still require additional cords/ thermocouple / etc...).

I'd like to convert my old kiln to a digital control. It is a Skutt 145. It's a bit odd, as it uses each hot leg of the 240V 4-wire outlet to run it's own set of 120V elements, sharing a common neutral. Does the attached schematic seem like a reasonable way to wire this?