Kiln Overfiring

[Bill Kielb]

1 hour ago, ShanRums said:

Do you think this could be the culprit? I couldn't find any other loose wires. Am excited to do another test tonight and see if it works! I only have 2 cones left though and they're sold out everywhere, so I hope this works :') 

If it was 100% unattached there would no reading, so maybe, definitely tighten and make good. Thermocouples increase in output as temperature goes up so a bad connection could give you a low reading but that would really speed up the firing because the controller would think it’s lower and fire harder. At 9.9 ohms (10%) your elements would be considered fully worn, so depending on the accuracy of your meter they don’t seem fully worn although 9.4 is halfway there.  Can you safely measure the voltage: Kiln off and kiln fully on just to see if we are losing a percentage energy there. It doesn’t take much so worth measuring I think. We also need to know the rated voltage and wattage on the nameplate to compare with the measurement.

Good find on the tcouple, but doesn’t seem likely that that would logically account for the symptoms. All else fire a test load, maybe some test bowls, add some mass as in shelves just to get closer to a normal load. It’s troubling because you have not fired a full load yet and your symptoms are, it is slowing above 1170. The good thing is you can monitor the speed and see if it slows down near the end. If so, we will need to find where the power loss is. Voltage measurement  (kiln operating- all elements) for sure if you can safely do it.  If the voltage is low that will be significant.

[neilestrick]

7 minutes ago, Bill Kielb said:

Good find on the tcouple, but doesn’t seem likely that that would logically account for the symptoms.

The thermocouple could definitely be the cause. It could be a bad connection somewhere along the TC system,  or a split in the weld that's opening up as the kiln gets hotter, or just a bad thermocouple (it happens).

@ShanRums Have you done a factory reset on the controller? Is there a thermocouple offset in the controller? Is there a protection tube on the thermocouple?

[ShanRums]

Ah.... so I was just rereading the controller manual, when I realised that I never set the type of thermocouple I have with the controller. It's set to an r type, when I have a s type. I'm guessing this is going to have a big impact on what temp the controller displays... I'm so sorry for wasting all of your times :') I feel so silly aha. 

Will update tomorrow once it's finished firing!  

[Babs]

1 hour ago, ShanRums said:

Ah.... so I was just rereading the controller manual, when I realised that I never set the type of thermocouple I have with the controller. It's set to an r type, when I have a s type. I'm guessing this is going to have a big impact on what temp the controller displays... I'm so sorry for wasting all of your times :') I feel so silly aha. 

Will update tomorrow once it's finished firing!  

And buy yourself some cones and drill a spyhole.  Not near thermocouples or elements.

Banks of cones one below target  one the target and one over target on different shelves in your kiln. You will fond out heaps and explain some differences you will experience.

Get behind the wheel of a car, set it on cruise and go to sleep!!!"No!!!!!!"!

I hear you cry. Same with firing a kiln.  Stay vigilante esp. towards end of firing.

Keep a log book so you can note any changes in time taken,  state of glazes etc at end of firing. to name but a couple of points.

[Bill Kielb]

2 hours ago, ShanRums said:

It's set to an r type, when I have a s type. I'm guessing this is going to have a big impact on what temp the controller displays... I'm so sorry for wasting all of your times :') I feel so silly aha. 

OMG! The one thing guaranteed to overfire your stuff! I assumed it came programmed with the kiln. Setting an R type thermocouple and using another type in its place is one sure way to over fire. Really good catch, a well known issue that happens on occasion and most manuals even warn of it. It’s rare to happen and really hard to figure out unless it’s obvious someone was in there changing it. Nice! And you got a lot of experience too.

Just be sure to confirm what type you have.

Edited October 5, 2022 by Bill Kielb

[Min]

6 hours ago, ShanRums said:

I'm so sorry for wasting all of your times :') I feel so silly aha. 

Not at all!!! It was an interesting thread on a few levels. 

[ShanRums]

7 hours ago, Bill Kielb said:

OMG! The one thing guaranteed to overfire your stuff! I assumed it came programmed with the kiln. Setting an R type thermocouple and using another type in its place is one sure way to over fire. Really good catch, a well known issue that happens on occasion and most manuals even warn of it. It’s rare to happen and really hard to figure out unless it’s obvious someone was in there changing it. Nice! And you got a lot of experience too.

Just be sure to confirm what type you have.

It's because the kiln didn't come with a controller, and so my friend let me have their old one! I remember reading it in the manual before I got the kiln but then completely forgot! 

Loads of experience, thank you all so much! 

Just watched the footage back and the kiln followed the ramps pretty much spot on, can't wait to open it up. 

[Babs]

Fantastic. Good luck.

Another investment which I think every kiln should come with is an independant timer which one sets about 15 or thirty minutes longer than estimated firing time. This timer is a kill switch for the kiln incase  the controller stops functioning properly and does not switch off. 

Glad you've got it sorted.