Thermocouple replacement choices

[Beekeeper]

My kiln is over-firing by at least two cones. This since moving several years ago and not doing any pottery for some times.

I tried adjusting the cone program two cones lower - still over firing. Thinking I will try replacing the thermocouple.

How do I determine the length of the thermocouple to purchase? The existing thermocouple pokes into the kiln chamber by nearly two inches. Is that too much?

Also, does anyone have a take on whether the Type K thermocouple is sufficient or is it worth investing in a Type S? My highest firings should be no more than Cone 6. My last firing was at least an 8, though. Would that high a temperature damage the thermocouple?

I am not shy about changing the thermocouple - I installed the 3K Electrositter on the kiln myself, have replaced controllers on other kilns and maintained kilns at a local arts council for years. So I have done kiln wiring for probably 20 years, though not so much recently. Rusty on the details on thermocouples and not finding any documentation.

So many questions. Thanks to anyone who can give me a hand on this.

[neilestrick]

Type K are fine for 99% of potters. They are accurate enough for most applications and are inexpensive. If you're doing something like crystalline glazes that require greater accuracy, or are firing regularly to cone 10, then type S may be worth the money.

Replace the type K thermocouple, with the controller set back to factory settings and see where you're at. Use self-supporting or large cones on the shelf. From there you should be able to calibrate the controller to fire accurately. As for length, it should project into the kiln about 1 1/2 to 2 inches.