Skutt 1027 underfiring on bottom with recently replaced elements

[flaxattack]

Hi ceramics community,

My previously reliable 1 phase, 240 volt Skutt 1027 has been underfiring, but only on the bottom shelf, for the past month or so. I’ve been in touch with Skutt customer service, but I figured it couldn’t hurt to crowdsource some opinions. Here are the details:

- I use cone fire mode on medium to cone 5 with a 12 minute hold

- the rest of the kiln seems to be firing to temp (the glazes look fine and the tip of the 5 cone touches)

- the bottom is visibly underfired and the 5 cone is not bent at all

- I replaced all of the elements about three months ago, and just re-replaced the bottom element last week (and no, I did not mix up the top/bottom and center elements)

- I replaced the thermocouple a couple of weeks ago

- I fire with staggered half shelves and there is an envirovent, so there shouldn’t be a circulation issue

- the amp readings are normal, so it’s not the relays

- the filled voltage reading is about 20 lower than the no load reading 

The difference in voltage readings made the Skutt service guy think it could potentially be an issue with the breaker wiring or maybe the transformer on our block. I’m a little skeptical about the wiring being an issue because the kiln has been in place and functioning normally for 5+ years. The transformer could be an issue because there is an apartment building being constructed next door, but there doesn’t seem to be much heavy machinery currently in use there. Skutt recommended getting in touch with the power company about the transformer and firing at night, which I intend to try,

Does anyone have any other ideas about what the issue could be or things to try? Thanks for reading the essay!

[neilestrick]

Skutt kilns, and all kilns with single thermocouples, tend to be finicky about how they are loaded. You need to load big stuff at the bottom, a tall shelf. Load smaller stuff in the middle (higher density, more mass), and the top somewhere in between. There's a tendency to load more dense at the bottom and less dense at the top, because it's easier to load tall stuff at the top, but that method can make the kiln fire very unevenly. I've seen them be 2 cones off at the bottom.

If you're getting low voltage from the service, that would affect all the elements, causing the firings to take longer. It wouldn't only affect the bottom elements. Are you getting low voltage on all 3 rings of the kiln , or just the bottom section? If it's just the bottom section, I'd replace all the wires and the relay. That might be a good idea anyway, because it's possible you've got a relay that is sticking occasionally and causing the bottom to lag behind, but not enough to throw the whole firing out of whack. Often they don't stick until they get hot, so it's a difficult thing to diagnose.

[Arnold Howard]

I would make sure the peephole plugs are inserted.

Arnold Howard

[flaxattack]

7 hours ago, neilestrick said:

Skutt kilns, and all kilns with single thermocouples, tend to be finicky about how they are loaded. You need to load big stuff at the bottom, a tall shelf. Load smaller stuff in the middle (higher density, more mass), and the top somewhere in between. There's a tendency to load more dense at the bottom and less dense at the top, because it's easier to load tall stuff at the top, but that method can make the kiln fire very unevenly. I've seen them be 2 cones off at the bottom.

If you're getting low voltage from the service, that would affect all the elements, causing the firings to take longer. It wouldn't only affect the bottom elements. Are you getting low voltage on all 3 rings of the kiln , or just the bottom section? If it's just the bottom section, I'd replace all the wires and the relay. That might be a good idea anyway, because it's possible you've got a relay that is sticking occasionally and causing the bottom to lag behind, but not enough to throw the whole firing out of whack. Often they don't stick until they get hot, so it's a difficult thing to diagnose.

This is very helpful, thanks! I try to load with taller shelves on bottom, but I do tend to pack the kiln pretty densely, so that could be an issue. I'm not sure about the voltage on the different rings, but I borrowed a multimeter today to check. Hopefully I'll find the culprit soon!