Controller or thermocouple?

[torchbynight]

One more question for y'alls.... My kiln has been having issues. When I 'boot it up' to get to my 950 holding temp, as it ramps up, it ramps up normally til it gets to say.. about 800. Then it goes weird. It'll ramp up fast to 950, pass it up to almost 980 (this varies- a LOT) and then drop back down to 880 or so, jumping back and forth. If I shut it down and restart it a few times, it'll settle down and work right, ramping up slowly to 950 (about 1 degree per second, not jumping up 5 at a time), and holding at 950). My question is- is this my thermocouple- I think that's what it's called, the thing that measures the temp inside the kiln- or is it a problem with the controller? It's on a dedicated circuit, all that good stuff, ad it just started happenig about a week ago. Anyone else ever had this problem or know what it is?

[Dale M.]

My "guess" is it may be the thermocouple.... You might want to do a little maintenance on kiln... UNPLUG IT and pull access panel off and check to see if all wiring and screw connections are tight... You problem could be as simple as a loose connection between thermocouple wires to controller....

Other thing may be that thermal couple is going bad at end where it is in kiln chamber, the connection between the two wires may be deteriorating and heading for total failure.... Least expensive part to replace would be thermocouple...

Dale

[torchbynight]

Thanks, Dale- I have an inkling it is the thermocouple, just wanted some input to see if anyone else had seen this :) I'll do as you said and check- does anyone know what type of thermocouple AIM uses in their kilns? I keep thinking it's a "K", I'll have to do some research.

[Dale M.]

Best thing may be to contact AIM directly and ask their tech people for an opinion and go from there...

Dale

[charrydolls]

I use a hot head torch that freezes up, if I buy a kiln with a bead door can I place the bead still on the mandrel in the kiln until I change my tank. Then can I retrieve the bead that is in the kiln and continue to work the bead?

[torchbynight]

You should be able to, just like healing a crack on an annealed bead. However, it's tricky- you have to SLOWLY introduce it back into the flame to make sure you don't thermal shock it. Holding it at 950 or so and then putting it in a 1200+ degree (I have no idea how hot that torch is...lol) flame is a shocker! Waft it through the flame like you're heating up a particularly shocky rod of glass :D

[smutboy420]

Its just sounds like your dead band range is set wrong. and its just takes awhile for your kiln to find equallibrum.
Most controllers have a setting to tell the controller how many degrees you want the temp to swing between. Say you have a dead band range of 10 degrees and have you temp set to lets say 950F the controller will stop power to the kiln when the temp hits 940 then it will heat up to 950 then shut off power to the kiln. But you will get some heat lag and the temp will still keep going up some as heat from the elements heats the kiln. Then it will not turn it back on till it drops back to 940 again.

Also if you controller has an autotune fuction on it DO try running the auto tune. Autotuning will heat your kiln up and let it cool a few times. While its doing that it will try to figure out how your kiln responds. Then the auto tuneing will set the controller to know how your kiln reacts and then it will know if it needs to start/stop heating at what ever temp it needs to get it to hold at the set temp.

Try the autotune if it has an autotune function. Then check the dead band range. It may also be called "range hi" and "range low" depending on the controller. You will probely need the book for your controller to find the settings you need. Or aim can adivise you I'm sure.

Then if either of them don't fix it Then start looking for some thing wrong with the kiln or controller. like the thermcople or relay.

[torchbynight]

I might have thought I had a setting wrong, but... I've been running this controller on the kiln for 3 years now, and it's just started having a problem in the last two weeks :)