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What I Need To Know About Changing The Thermocouple.


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#1 Karen B

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Posted 21 June 2014 - 02:29 PM

I spoke to Skutt tech support about some temp problems.  I put in a new thermocouple. It is the newer inexpensive style. The one I replaced is not made anymore. It was old and possibly responsible.  Some facts: Cone 6 firings, electric skutt 1027 kiln. About 100 firings in. More than half were cone 04.

 

I still had what I viewed as a problem (glazes vary from looking not good to just looking different) after one cone 6 firing, so I called Skutt again. Apparently, according to the tech, when you change the thermocouple you have to re-calibrate the kiln by comparing old cone tests with new cone tests. First I heard of that! I don't save the old cone tests. Do you? So now I need to run a firing with tests of all my glazes and figure out how to "calibrate" to get them to look like they used to. 

 

Has anyone experienced different results after changing the thermocouple? Did you know about this?

 

I realize there are many mechanical issues involved in accurate temperature readings in firing, but I appreciate it if you could help me with this one particular issue. Thank you so much!

 

Karen

 



#2 Wyndham

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Posted 21 June 2014 - 02:47 PM

Karen, the better thing to do right now is to compare(as best you can), a piece from an older firing before the new T/C and what just came out. Does one look over or under fired? Did one run more than another?

Start by putting cones in each shelf c5,c6,c7.

The calibration will be adding some hold time if the new firings are too stiff. You will need to do only one adjustment at a time.

The other thing to consider is the age of your elements, were the firing going longer between firings?

There are several things that you need to take notes on as well as remembering how long (aprox) the old firings took and compare that to the new T/C firings.

I'm sure others will have more info for you as this goes along

Wyndham



#3 Babs

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Posted 21 June 2014 - 07:11 PM

I don't have a new fancy kiln but my log of firing is a bible worth having and if you're not keeping one now, start today. Memory tells lies and creates myths to suit the moment!



#4 Karen B

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Posted 22 June 2014 - 05:38 PM

Thank you Wyndham and Babs for your helpful suggestions.

Babs, you are so right about memory lying! 

 

Karen



#5 Karen B

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Posted 23 June 2014 - 09:04 AM

Still wondering if others have had a change in firing  results after installing a new thermocouple?



#6 Biglou13

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Posted 23 June 2014 - 05:12 PM

Yes.

(I learned a lot helping group/guild studio change t/c
and calibrate kiln)

Had to change. We just ran a few loads with cones 5 6 7 ended up having to make kiln hotter.
http://skutt.com/ima...nstructions.pdf

That is using cone fire mode.

But I get better results with custom ramp hold programs. And end up adjusting end temp, and hold time.

Yes I expected to need to calibrate. Unlike men, All thermo couples are not created equal. Chances are you're firings with old thermocouple were not correct either.

Unless you were firing cones prior to change. You will have to choose calibrate to cone, or calibrate to glaze performance.

Sounds like you didn't save or are familiar with previous cone performance prior to change..... I'd get kiln to proper cone first. Then adjust if necessary for glaze performance.

So yes you may have to sacrifice kiln load. Ok it's not that bad. Ours was off but still within ballpark. Yes kiln has to be loaded to calibrate to cones. According to skutt you need to leave 2 inches open in all directions around thermocouple. And you have to fire a full load. If you don't want to sacrifice a kiln load, load kiln with rejects, that you haven't thrown away.

Unfortunately one must deal with and understand some technical issues to insure consistent performance.

After you finally get it calibrated. I'd still run one cone for final temp in each firing until satisfied it set properly. From then only periodically or if you make any changes.

To further complicate you may have differences in cone performance in different parts of kiln. Like-- bottom of kiln is firing 1/2 cone cold, or hot. Hopefully it's a loading issue. If not then "Huston we have a problem". Which in our case led to diagnosing kiln with failing elements. (Elements outside of appropriate ohm range)

Hope that helps, and answer is not clear as mud.
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#7 Karen B

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Posted 23 June 2014 - 07:26 PM

Yes.

(I learned a lot helping group/guild studio change t/c
and calibrate kiln)

Had to change. We just ran a few loads with cones 5 6 7 ended up having to make kiln hotter.
http://skutt.com/ima...nstructions.pdf

That is using cone fire mode.

But I get better results with custom ramp hold programs. And end up adjusting end temp, and hold time.

Yes I expected to need to calibrate. Unlike men, All thermo couples are not created equal. Chances are you're firings with old thermocouple were not correct either.

Unless you were firing cones prior to change. You will have to choose calibrate to cone, or calibrate to glaze performance.

Sounds like you didn't save or are familiar with previous cone performance prior to change..... I'd get kiln to proper cone first. Then adjust if necessary for glaze performance.

So yes you may have to sacrifice kiln load. Ok it's not that bad. Ours was off but still within ballpark. Yes kiln has to be loaded to calibrate to cones. According to skutt you need to leave 2 inches open in all directions around thermocouple. And you have to fire a full load. If you don't want to sacrifice a kiln load, load kiln with rejects, that you haven't thrown away.

Unfortunately one must deal with and understand some technical issues to insure consistent performance.

After you finally get it calibrated. I'd still run one cone for final temp in each firing until satisfied it set properly. From then only periodically or if you make any changes.

To further complicate you may have differences in cone performance in different parts of kiln. Like-- bottom of kiln is firing 1/2 cone cold, or hot. Hopefully it's a loading issue. If not then "Huston we have a problem". Which in our case led to diagnosing kiln with failing elements. (Elements outside of appropriate ohm range)

Hope that helps, and answer is not clear as mud.

 

 

Yes BigLou, that helps tremendously. I have made about 100 test cups and tiles to test glazes and fill shelves. I will add some various paraphernalia and kiln furniture from around the studio to fill it up.  Thank you so much for the link and the info!

I am pretty much out here on my own in suburbia, so rely on this forum for info one would normally pick up in a group setting. I was advised by Oldlady to find a guild.

Thanks!



#8 Biglou13

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Posted 23 June 2014 - 08:00 PM

If you have or get a electronic multimeter. Got mine from lowes. It will be easy to check resistance of elements. Just to rule out other issues. Which is prolly the next step in trouble shooting. Temp issues.

Skutt has good tech support when you can reach them they stay busy.. They are the best resource. I had to dumb down a lot of what they said to pass it on to other members.

As an artist all this technical stuff seems anal, but it make sure your work is consistent and ultimately frees us up creatively.

Working on the kiln isn't that hard, it's just a bit intimidating

The furniture is great filler we did the same.

We are your online guild

Now that I'm getting to understand firing. I realize different heating and cooling programs affect glazes differently. Our glossy black doesn't like controlled cooling, while our red needs it. There a whole world other than medium speed cone 6 button.
Caution big brother is watching.
The beige is blinding!!!!!!
The middle of the road is boring

The true sign of intelligence is not knowledge but imagination.
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#9 Karen B

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Posted 24 June 2014 - 12:50 PM

If you have or get a electronic multimeter. Got mine from lowes. It will be easy to check resistance of elements. Just to rule out other issues. Which is prolly the next step in trouble shooting. Temp issues.

Skutt has good tech support when you can reach them they stay busy.. They are the best resource. I had to dumb down a lot of what they said to pass it on to other members.

As an artist all this technical stuff seems anal, but it make sure your work is consistent and ultimately frees us up creatively.

Working on the kiln isn't that hard, it's just a bit intimidating

The furniture is great filler we did the same.

We are your online guild

Now that I'm getting to understand firing. I realize different heating and cooling programs affect glazes differently. Our glossy black doesn't like controlled cooling, while our red needs it. There a whole world other than medium speed cone 6 button.

 

 

 

Thanks Biglou, we are in sync. Picking up a multi meter is next on my list. I am hoping I will not have to change the elements. I received some help here so I am not so nervous about it, but the cost is steep. I have done other things which just required following directions, like replacing the relays, and putting a new motor in my vent, but figuring out heat work is a little over my head, or at least I think it is.

 

I have been doing a cool down program for years, which bring out the speckles in my stoneware nicely. But, when I spoke to the guy at Skutt, he said he never heard of a cool down program like mine(with attitude). So now I am wondering if I have been doing it wrong. I hold at several temperatures and let the kiln cool from one to the other without putting in a rate to slow the cooling from one to the other. But I start holding at 1800 and let it drop at 50 degree intervals until 1550 with the longest hold at 1600. 

 

ps, I love that you say "prolly". It is my favorite new word.



#10 Arnold Howard

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Posted 25 June 2014 - 11:54 AM

I have been doing a cool down program for years, which bring out the speckles in my stoneware nicely. But, when I spoke to the guy at Skutt, he said he never heard of a cool down program like mine(with attitude). So now I am wondering if I have been doing it wrong. I hold at several temperatures and let the kiln cool from one to the other without putting in a rate to slow the cooling from one to the other. But I start holding at 1800 and let it drop at 50 degree intervals until 1550 with the longest hold at 1600.

There are many ways to program the Ramp-Hold mode. To slow the cooling, most people add a segment that contains a specific cooling rate. Adding segments with holds and full rates, as you have done, is another way to achieve similar results. (The full rate allows the kiln to cool at its normal cooling rate.)

 

Including witness cones on at least one shelf in every firing will simplify the calibration of a new thermocouple. The witness cones will also alert you if the thermocouple begins to drift in temperature.

 

Sincerely,

 

Arnold Howard

Paragon Industries, L.P., Mesquite, Texas USA

ahoward@paragonweb.com / www.paragonweb.com



#11 Karen B

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Posted 27 June 2014 - 12:50 PM

Thanks Arnold.






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