I have a paragon TNF24 that I wanted to fire this past weekend. After loading the kiln and programming the DTC800 controller and hitting start I was disappointed to have "FAILED" displayed. After many attempts I resorted to reading the manual and determining through several diagnostic tests that the thermocoupling was bad. Sure enough when I removed it it had a break in the probe that goes through the wall of the fire brick.
Now my question:
Do all thermocouplings act the same? Can I just go to the local hardware/heating company and get another thermocoupling or does it need to be specifically ordered for the kiln? Do all thermocouplings generate the same milliamp current?
Short answer, no, you can't get a replcement at the local hardware. The shortest route will be to get a replacement from Paragon to match your model.
A longer answer is that there are 3 types if thermocouples used in kilns. 'K', 'S', & 'R'. You need the type to be matched for what your controller is made [or configured] for.
I have done a very cursory search on thermocouples on Google, but did not land a spot that talks about the exact max temp for each type.
If the manual for your uinit doesn't discuss it - check Paragon's website. The bottom line is that you need one speced to the controller.
wingoda wrote:I have a paragon TNF24 that I wanted to fire this past weekend. After loading the kiln and programming the DTC800 controller and hitting start I was disappointed to have "FAILED" displayed. After many attempts I resorted to reading the manual and determining through several diagnostic tests that the thermocoupling was bad. Sure enough when I removed it it had a break in the probe that goes through the wall of the fire brick.
Now my question:
Do all thermocouplings act the same? Can I just go to the local hardware/heating company and get another thermocoupling or does it need to be specifically ordered for the kiln? Do all thermocouplings generate the same milliamp current?
Thanks in advance....
Paragon lists the thermocouple for your kiln on their webpage. You can order one from them.
Another thing to do is check your local ceramic shops and supply stores. Your kiln is fairly standard and parts may be available locally. The thermocouple type for your kiln is "Type K".
K type thermocouples are a maintenance item. They deteriorate (actual corrosion from the dissimilar metals, you can see the "green rot" happening on a large wire diameter one) with time and heat and eventually don't read correctly any more, or, as in this case, let go entirely.
I keep a roll of fairly thick gauge K type thermocouple wire around. I strip the insulation back, twist the ends together and melt the very end of the twist together with a torch and a bit of borax for flux and I have a new thermocouple.
This makes it less painful financially to change 'em out yearly. The thermocouple wire is the same metals but a lot cheaper than an actual thermocouple. Not to mention being able to make one up when the stores are all closed and you need one now.
Dani wrote:Thanks, Dave.... that's got to be the tip of the year! Still trying to figure out why thermocouples cost as much as they do.
They have them and you need one, so you get to pay.
Actually the wire is somewhat expensive because the alloy has to be certified and inspected if it's going to be used for any accurate temperature measurment. Buy one that has been calibrated and the price goes up and up.
Another trick that will work with a thermocouple is to twist the wires together and soft solder them. This only works for temperature measurements below the melting point of the solder. The introduction of a third metal (solder) does not effect the performance.
We make thermocouples at work using silver solder flux and a carbon arc to fuse the wires. The ends of the wire just melt into a little ball.
Dani wrote:Thanks, Dave.... that's got to be the tip of the year! Still trying to figure out why thermocouples cost as much as they do.
Much of the expense of a thermocouple can be the sheath that it is encased in. I have been using the same type K theromcouples for 12 years now and I have had no problems. My anneals are still right on the money. My thermocouples are encased in inconel steel. They are industrial grade and probably cost quite a bit more than the cheapies that most companies try and get away with. I am not familiar with what mine cost because I got them from my dad for the right price. They are from Barber Coleman (now Eurotherm).
