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Amaco HF-105 temp issues


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Our school has two HF 105 kilns. Worked great for about 5 years and started having temp issues. Very long story short, turns out even though the power box said 240, we weren’t getting that amperage. Electricians installed a booster so now we do. Here’s the weird situation: according to witness cones,  kilns aren’t reaching 04 in bisque (they get to 06 and sometimes near 05). But they reach 5 and 6 no problem in the glaze fire. Elements are good, thermacouples have been replaced, relays as well. We have offset the temp 20°, programmed holds, I do candle for a while on bisque as well. Why would the kilns struggle to reach 04 but reach a hot cone 5/6 no problem? Thoughts?


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Is it "struggling" to get to cone 04, or does controller need calibration so that it turns itself off at the proper temperature? If the glaze firings are reaching the expected results according to witness cones, leave the overall thermocouple offset alone and set a cone offset for cone 04. Instructions for this should be in the user manual.

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Ahhhh! Thank you! When we did the offset we entered using the 9 not realizing that was a negative. The manual we were looking at didn’t explain it as clearly as these instructions you’ve provided and only showed the offset with the 9 (for example, 9020 for 20 degrees). I believe this is our problem! Our maintenance crew has all but given up. Thank you!!

Edited by LIT
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Hello again,

So it appears our kiln controller is different. In the manual, it explains that the using the 9 for programming the TCOS makes it hotter. I tried it anyway with 20 instead of 9020 for a 20 degree offset  and it didn't even reach ^ 06.  Also, there does not appear to be a way to program an individual offset per cone, only a general TCOS. I've emailed Amaco and am awaiting confirmation on that point.

Any other thoughts or ideas? 

Thank you,


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