Skutt kiln skipped a hold - no error code displayed

[JRW]

Hi All, 

 

I have a new Skutt KM 1227 and am doing my first glaze firing (I’ve done one break-in firing and one bisque firing before).

 

I programmed the kiln to rise by 108f/hr to 195 degrees and hold for a few hours for a pre-heat (I was using shelves that were slightly damp from kiln wash). 
 

For some reason the kiln just blew past that temperature and was at 216 before I caught it. I stopped the firing to let it cool a bit, then started it again, this time ramping to 200 degrees for the hold. Again, the kiln went up to 267 before I noticed it wasn’t holding.

 

the user manual says there will be an error code if the kiln stays more that 50 degrees hotter than the hold temperature for a given segment for at least 18 seconds. This situation met those criteria but there was no error displayed.

 

I’m just curious if anyone knows what might be causing this? I’m having trouble reaching Skutt and am on a deadline. I let the firing proceed but am worried the kiln won’t recognize the other holds I programmed. I didn’t program any holds in the bisque firing i did. Thanks!

[Bill Kielb]

While it is possible to have a defective controller, I would change the ramp rate to something smaller and test empty. 108 degrees per hour plus room temperature gets you to set point really quick and 108 degrees per hour is really a desired end of firing rate for the last 200 - 250 degrees of a firing. I would try 50 degrees per hour just to test for success at a lower rate. If it passed that test then try 108 degrees and see if you can reproduce the failure.
Not saying this is a programming error but I have seen similar reactions when 15 minutes was entered instead of 1.5 hours or some combination to that effect.   I think it could be defective but would suggest proving it out and making sure it is not a programming issue.
Stuck relay error -  An error would be generated for a stuck relay occurrence but this most often reveals itself as the kiln will not fully cool unless you are unlucky and the relay sticks when heated and unsticks later. Either way in a new kiln it is very unlikely but anything is possible.

As far as other holds, not sure what they could be but a reason to figure out if this is a programming issue if you are dependent on holds through your firings.

Edited November 23, 2022 by Bill Kielb

[JRW]

1 hour ago, JRW said:

Hi All, 

 

I have a new Skutt KM 1227 and am doing my first glaze firing (I’ve done one break-in firing and one bisque firing before).

 

I programmed the kiln to rise by 108f/hr to 195 degrees and hold for a few hours for a pre-heat (I was using shelves that were slightly damp from kiln wash). 
 

For some reason the kiln just blew past that temperature and was at 216 before I caught it. I stopped the firing to let it cool a bit, then started it again, this time ramping to 200 degrees for the hold. Again, the kiln went up to 267 before I noticed it wasn’t holding.

 

the user manual says there will be an error code if the kiln stays more that 50 degrees hotter than the hold temperature for a given segment for at least 18 seconds. This situation met those criteria but there was no error displayed.

 

I’m just curious if anyone knows what might be causing this? I’m having trouble reaching Skutt and am on a deadline. I let the firing proceed but am worried the kiln won’t recognize the other holds I programmed. I didn’t program any holds in the bisque firing i did. Thanks!

Thanks, those are good ideas. I’m almost certain that I programmed the hold time correctly but it did occur to me that could be the issue. But twice?
 

The only other thing is that when the kiln was past the desired temp and I stopped the firing and restarted it, it was already above 200 degrees. (200 was the desired hold temp). So I assumed it would cool to 200 and then hold, but instead it just kept heating. I don’t know how the kiln algorithm handles a situation where it is supposed to be ramping up to a temperature but starts the firing program already above that temperature.

 

I will do a test on empty at a lower interval as you suggest. Thanks again!

[Babs]

What controller do you have?

Whenyou stopped it and restarted it, what ramp did u notice it was displaying?

I am thinkinh like Bill, miutes instead of hours entered. Can you flick thro the ramps to see what u entered?

[High Bridge Pottery]

Does it have a review button so you can make sure the program is correct and rule out that being wrong?

[neilestrick]

In the first instance, it should be able to handle the 108F/hr ramp just fine. I ramp my kilns at 200F/hr to 200F for preheating and it works. It could be that it overshot just a little bit but was still happy since it was still within the acceptable parameters, or more likely that you put in a hold time of minutes instead of hours. It happens. I've done it myself. It's hours to the left of the decimal, minutes to the right. In the second instance, it skipped the hold because you were already hotter than the hold temp. It will not cool to get to a temperature unless you program it to cool.

[JRW]

9 hours ago, Babs said:

What controller do you have?

Whenyou stopped it and restarted it, what ramp did u notice it was displaying?

I am thinkinh like Bill, miutes instead of hours entered. Can you flick thro the ramps to see what u entered?

I have a KM controller. I wasn’t able to see what segment it was on - maybe there’s a way to do that while the program is running but I don’t know how.

[JRW]

5 hours ago, High Bridge Pottery said:

Does it have a review button so you can make sure the program is correct and rule out that being wrong?

I pressed the review button while the program was running but nothing happened…

[JRW]

9 minutes ago, neilestrick said:

In the first instance, it should be able to handle the 108F/hr ramp just fine. I ramp my kilns at 200F/hr to 200F for preheating and it works. It could be that it overshot just a little bit but was still happy since it was still within the acceptable parameters, or more likely that you put in a hold time of minutes instead of hours. It happens. I've done it myself. It's hours to the left of the decimal, minutes to the right. In the second instance, it skipped the hold because you were already hotter than the hold temp. It will not cool to get to a temperature unless you program it to cool.

Thank you, that’s helpful! 

[Dick White]

On 11/23/2022 at 12:12 AM, JRW said:

{snip}

The only other thing is that when the kiln was past the desired temp and I stopped the firing and restarted it, it was already above 200 degrees. (200 was the desired hold temp). So I assumed it would cool to 200 and then hold, but instead it just kept heating. I don’t know how the kiln algorithm handles a situation where it is supposed to be ramping up to a temperature but starts the firing program already above that temperature.

{endsnip}

Bingo! There is the problem. A little-known factoid (don't know if it is documented in the Skutt manual, so much in the Skutt manual is not) with the Bartlett controllers (yes, Skutt uses a slightly modified private label version of a Bartlett controller) is the first segment of any program (both cone-fire and ramp-hold) must be a heating ramp to a higher set point than the current starting temperature. For the first segment, you cannot make it decrease in temperature. Any subsequent ramp can be a cooling segment, but not the first. If you ask it to do something it can't do, it will skip that segment. It was already above 200 and you asked it to go down to 200. It said "too bad, so sad" (the screen is not wide enough to display that error message) and moved on to the next segment. When restarting a buggered preheat, you have to let it cool a bit on its own (pop the lid slightly?) until it is below the preheat set point and then restart the program.

Edited November 26, 2022 by Dick White
corrected poor grammar