Thermocouples are the temperature sensing probes that protrude into your kiln chamber and feed information to your controller. Just like elements they can degrade over time.
Again, it depends on the temperatures you are firing too and the amount of combustibles they are exposed to that determines how long they will last. If you are only firing your kiln to glass fusing temperatures (between 1400 F and 1500 F) you may never need to change your thermocouple. If you are firing cone 10 crystal glazes and holding at high temperatures (over 1800 F), you may only get 20 firings out of one.
There are many different types of thermocouples but the standard is the Type K. Check with your dealer or manufacturer to be sure which one you have before you order your replacement.
Monitoring Your Thermocouple
When your thermocouple is approaching the end of it’s useful life you will notice that your kiln will fire a little hotter each firing. If you are firing ceramics you will want to use a pyrometric cone to monitor your thermocouples accuracy. These are available through most ceramic suppliers. They can recommend the type of cone you will need when you purchase your clay and glazes.
Place the pyrometric cone on a shelf about 2 inches from your thermocouple, brick and any ware you have on that shelf. When the cone bends over and touches the shelf, you should change your thermocouple.
Inspecting Your Thermocouple
It is not uncommon for people to accidently hit their thermocouple when loading the kiln. If you ever bend or crack a thermocouple, replace it right away.
Some thermocouple are exposed and some of covers. Both have their advantages. If you have an exposed thermocouple you can see how much it has degraded. If it begins looking like the image to the left it is a good idea to change it.
Exposed thermocouples can flake, so it is a good idea to brush it off with an hold toothbrush every once in a while.
Replacing Your Thermocouple
Replacing your thermocouple is something most kiln owners should learn. It can take as little as 5 minutes and usually only requires a screwdriver. Learn to follow your manufacturers instructions for replacing the thermocouple for your model and you can save a lot of time and money.
Manufacturer Links – Replacing A Thermocouple