Paragon LT-3 Kiln Over Firing

[leigharttx]

Hi All!

I've recently been having issues with my kiln over firing. I contacted Paragon and they sent me the kiln sitter operating manual. One of the adjustments within the manual says to check the position of the release claw and weight trigger. I've done that and re-situated it as shown in the manual. My sensing rod is centered and there's no decay from firing that I can see. Without test firing, I realize, it will be difficult to determine if this small adjustment is all that needed to be done; however, it just doesn't make sense to me that this would be the cause. Am I missing something or could it really be THAT simple? 

 

-Whitney 

[Benzine]

Are you using cones or bars?

I've only ever used cones, but I've seen poster here say, the bars are more reliable, due to the whole thing being the same thickness.

[leigharttx]

I'm using cones, I prefer bars but until now I haven't had any issues. 

Thanks! 

[Benzine]

Does your kiln also have a back up timer?

Do you keep a log, so you have a rough idea of firing time?

In either case, you could use some self-supporting cones, in front of the peeps, but also put a  cone, in the sitter, each firing.  

Make an adjustment to the sitter, but have a timer (if applicable) and the witness cones as backups.  

It may take a couple firings, but you should be able to hone in on the correct adjustment.

 

[leigharttx]

I adjusted the sitter and the weight yesterday and fired to 016 to no avail; it still over fired. While I was making adjustments, I did see a relay wire that was corroded but I can't seem to find a replacement online. Never having encountered this issue, I'm unsure if I can replace kiln wires with "normal" high temp relay wires from Lowe's or Home Depot? Other than that wire, I'm unsure of what other adjustments would have an effect. The wire, in my mind, is the only contributor to the problem unless I'm not considering or seeing other things. (Which is highly likely.)

[Min]

I think you have 2 issues going on. Since the sitter functions  mechanically, when the cone bends it should shut off. You adjusted it with an adjustment gauge like this?  If it trips freely then it should shut the power off to the elements, have you tried tripping it manually (cold kiln and power off)  to make sure everything moves freely?  Worn parts, bad cones or not properly adjusted sitter will cause issues.

Depending on the amount of corrosion you have on the relay wires you get into a cycle of increased resistance causing more heat which increases the resistance further which eventually ends up in burned wires / arcing and a non functioning circuit. Should be able to get high temp replacement wire from your pottery supply store. I don't know what they carry at big box stores.

[leigharttx]

Yes, I used the gauge, everything moves freely, there's no hang up between the weight/trigger. I haven't changed cones, I generally fire at cone 6 and that's the temp I noticed it was over firing. 
I've emailed Paragon about the wires, I bet they come back with a response. Thanks for your response! 

[Babs]

I always use the sitter as a "final shut off..I.e. if I drop off the perch. I control the shut off by temp and cone change.  Cones placed as Benzine says in  view from peep holes.  Sitter  a safety device.... but it's good to know it trips at approx right time.

What speed are you firing At? This also can affect the temp at which the kiln sitter cone lets the bar drop.

[neilestrick]

By how much is it over firing? How do you know it's over firing- just by the bend of the cone?

[leigharttx]

On 8/15/2018 at 6:51 PM, Babs said:

I always use the sitter as a "final shut off..I.e. if I drop off the perch. I control the shut off by temp and cone change.  Cones placed as Benzine says in  view from peep holes.  Sitter  a safety device.... but it's good to know it trips at approx right time.

What speed are you firing At? This also can affect the temp at which the kiln sitter cone lets the bar drop.

I haven't changed my firing times, this just started happening recently. I keep a log of my firings and I've been through it. This is purely mechanical for once. 

[leigharttx]

On 8/15/2018 at 9:36 PM, neilestrick said:

By how much is it over firing? How do you know it's over firing- just by the bend of the cone?

Yes, the cone is bent nearly in half when it's all said and done. On top of that, my cone 6 glazes are crawling every which way but back together. I've fired these in a full kiln, in a semi-full kiln, in a not so full kiln and all come out looking gorgeous until recently. I can re-fire, of course, I don't want to, especially not until I get this all sorted out. 

Thank you everyone for your responses. I'm itching to get this figured out! 

[Babs]

New batch of glaze....thicker application. Is the sitter the only control of end of firing.

May need a sitter rod replacement but how do you know if the sitter cone is your only indicator of final temp/ beatwork done

[leigharttx]

It's not the glaze, it's not the application, it's not the rod, it's not the weight and trigger. I've checked all of these things and the only problem I've seen within all the inner workings is a corroded wire. 

[Pres]

When manipulating the cone bar from the inside of the kiln, will the outer bar drop without any problems? Reason I ask is that once I had a kiln that the setter was not entirely lined up, it was leaning in at the top. This caused the outer bar to rest against the kiln when the cone went down. . . . . just a thought.

 

best,

Pres

[leigharttx]

2 minutes ago, Pres said:

When manipulating the cone bar from the inside of the kiln, will the outer bar drop without any problems? Reason I ask is that once I had a kiln that the setter was not entirely lined up, it was leaning in at the top. This caused the outer bar to rest against the kiln when the cone went down. . . . . just a thought.

 

best,

Pres

Thanks for your response, Pres. No, there's never been a hang up there causing a longer firing time. The weight and trigger and rod all work properly. 

[WoodlandPotter]

Hi.

Are the cone supports straight? It's possible if they are a little warped inward, that might cause the problem.

 

[leigharttx]

29 minutes ago, WoodlandPotter said:

Hi.

Are the cone supports straight? It's possible if they are a little warped inward, that might cause the problem.

 

Yes, everything is normal. Thanks!

[Babs]

A ell sounds like if you replace that wire you're sorted.

The sitter rod diminishes in diameter over time...May be visually ok but can affect  the drop...just saying

The other thing I had to do to get the drop aligned to the cone I was aiming for was to adjust where the little latch sits so the "drop bar" was sitting a little off vertical.

Can' see how a corroded relay would be the culprit  but hopefully you'll let us know.

[neilestrick]

On 8/17/2018 at 6:42 PM, leigharttx said:

Yes, the cone is bent nearly in half when it's all said and done. On top of that, my cone 6 glazes are crawling every which way but back together. I've fired these in a full kiln, in a semi-full kiln, in a not so full kiln and all come out looking gorgeous until recently. I can re-fire, of course, I don't want to, especially not until I get this all sorted out. 

Thank you everyone for your responses. I'm itching to get this figured out! 

The cone/bar in the sitter should be bent at 90 degrees. If it's more than that, then the sitter needs to be adjusted. Where the claw holds the weight, there it a plate that can be adjusted up or down. If it's over firing, then the plate needs to be moved down so the sitter releases it sooner. It doesn't take much. Also make sure the claw is in the correct spot on the rod. With the weight up all the way and the claw down, it should be about 1/16" from the plate on the weight.

[Babs]

Kiln wash on cone supprting surfaces of sitter parts..

[leigharttx]

Yeah, I adjusted all of the sitter parts first and test fired and the cone was bent in half and nearly touching end to end. The weight had fallen or was adjusted too low from the trigger, but I couldn't fathom how that would have caused an over fire. I've never noticed it being too close (hanging) on the trigger or not holding during firing either. I went ahead and adjusted it to the recommended 1/16" the adjustment guide said to. I'm in contact with Paragon and I'm going to order new relay wires. I'm almost positive that that's the culprit. 

 

Thank you all for your recommendations and suggestions on this! I'm ready to have my kiln back to normal. 

[neilestrick]

@leigharttxIf the cone is bent more than 90 degrees, then the sitter adjustment is the problem. It means the cone has to bend too far before the weight will drop and shut off the kiln. To fix that, lower the plate on the front of the weight where the claw contacts it. Relay wires have nothing to do with how hot the kiln gets other than sending electricity to the relays. If the wires were a problem, then the relay wouldn't work and the kiln wouldn't get hot enough, not over fire.

[leigharttx]

Hi Neil,

Thank you for your response. I adjusted the weight to the recommended 1/16'' because the weight was already set (too) low or so I thought. I'll try adjusting it lower, I'm just afraid of setting it too low that it won't reach the trigger and hold. 

On the other hand, if that wire is corroded, shouldn't it be replaced? It looks like a fire waiting to happen. 

Thanks, 

[neilestrick]

49 minutes ago, leigharttx said:

Hi Neil,

Thank you for your response. I adjusted the weight to the recommended 1/16'' because the weight was already set (too) low or so I thought. I'll try adjusting it lower, I'm just afraid of setting it too low that it won't reach the trigger and hold. 

On the other hand, if that wire is corroded, shouldn't it be replaced? It looks like a fire waiting to happen. 

Thanks, 

Yes, you should definitely replace the corroded wires, but they won't affect the over firing.  Only the sitter controls the final temp. If you can't adjust it lower and get the claw to hold, then you may have a bent sitter rod, or the claw is too far forward on the end of the rod.