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12" kiln having trouble keeping up temp


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Hi all,

I have a 12" 120v top load used kiln, brand name is Crucible from Seattle Pottery. It is having some trouble keeping up with the kiln schedule, I just wanted to ask if this is pretty normal for these little guys or if new elements etc. might improve things. I set it on full power and checked the elements and they are all glowing, no dark spots.

It has a Bartlett controller and I run the following program-

150/hr to 220
400/hr to 1978
100/hr to 2210 hold 10 mins
 
Ambient temp is in the 70's
 
From around 1700 degrees it starts slowing and only rises 200/hr at the end of the 400/hr ramp. With the 100/hr ramp it goes as slow as 30 degrees an hour towards the end. It also has trouble holding at 2210 and usually drops below 2200 during the hold and doesn't make it all the way back up to 2210.
I also tried firing up to 2232 but it gave an error E-1, which the manual says it couldn't increase temp faster than the minimum.
 
It still gets the job done just fine, but just curious if this is somewhat normal for the tiny kilns. Thanks!
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Sounds like elements are worn. Check with an ohm meter they can only increase about 10% in resistance then they are worn and need replacement. Not sure what the hold is all about, make sure it fills a real need though would be the suggestion. Definitely sounds like worn elements though. It’s good to know how many firings are on a set so I would suggest noting what number firing when you change them and start measuring things when they approach 100 firings. If you track your total time fired it will often trend upward and folks often learn their kiln just by how much longer it takes to fire.

Edited by Bill Kielb
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120V test kilns don't have a lot of power. It won't be able to keep up with a 400F/hr ramp, but I would expect it to be able to run 250-300F/hr at least up to 1900F or so, and it should be able to run 100F/hr at the end. Holds can be tricky on a kiln that doesn't have a lot of power. When the kiln first reaches peak, it's not uncommon for the temp to drop a little when it starts the hold, as it takes it a couple minutes to get into rhythm of the hold. Tiny kilns also don't have a s much mass to hold heat, so the elements have to work harder to do the hold. How old are the elements? Sounds like they may need replacing.

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