SNF 82-3 with kiln sitter cutting off after 4 hours for cone 04

[P Maxwell]

I have an older paragon SNF82-3 that I just had new elements installed. This kiln has a kiln sitter. I fired for first time empty to a cone 04. The kiln was empty except for shelves and witness cone. It is 2 phase. I set based on instructions to 4 on top dial and 2 hr on bottom for timer to initiate phase 2. I was shocked when it cut off in 4 hours. This is a smaller kiln but that seems too fast. Can anyone tell me if this is normal and if not suggestions on next steps.

Edited October 9 by P Maxwell
Wrong model

[neilestrick]

@P Maxwell Welcome to the forum!

Those small kilns often have more power per volume than the larger kilns. Can you post a picture of the controls? 

[P Maxwell]

[neilestrick]

This kiln is one of those oddball kilns that was one of the early versions of an 'automatic' kiln before digital controllers came out. It looks like the only way to slow down a firing would be to set the #2 timer to a higher number so it takes longer before the second stage kicks in, and setting the #1 top switch at a lower number and then possibly turning it up later as needed. The problem is that once the timer hits zero, the second set of elements goes on full power, which means it'll rocket up at that point. Is it wired so elements 1 & 3 are on one switch, and 2 & 4 are on the other? If you don't know, set the #1 switch to 1 and the #2 timer to On, let it run a few minutes, then carefully crack the lid and see which elements glow. 

HERE is a manual if you don't have one.

[PeterH]

That manual states (for the two-stage kilns)
switch #1 - elements 2, 4, 6 & 8
switch #2 - elements 1, 3 , 5 & 7

Which seems consistent with the wiring diagram.
https://corp.paragonweb.com/wp-content/uploads/8341151F.pdf

[P Maxwell]

[P Maxwell]

Yes every other element comes on in phase one as you describe. Then all come on in phase 2. Here is a pic of the cones.  So at this point I will set the ramp up slower (using timer switch) and then set the top switch to lower than it suggest for given cone. What I am not sure now is how long should I try to  target the length of firing? 6 to 8 hours for cone 04??

[Dick White]

In the newer digitally-controlled kilns, the computer controls the speed at which the kiln heats and thus the length of time a firing will take. Firing to a particular cone will always take the same length of time (until the elements begin to wear out and just can't keep up the speed). In a manual kiln, the elements are just on all the time (though the switching mechanism will change how many are on at a time and the state of their connection, i.e., parallel or series to adjust the amount of total heat being produced) and thus the length of the firing is a function of how much thermal mass (i.e., ware) must be heated by the electrical heating power available from the elements. More stuff in the kiln will take longer to heat, less stuff will heat to the target cone is a shorter time. You fired it empty except for the shelves and posts. Plain air is easy to heat, gonna hit cone 04 fast. Now that you have seasoned the new elements with an empty firing, try again with a full load and the time will be closer to your expectations.

[P Maxwell]

Thank you for the help!

[neilestrick]

I would shoot for 8 hours if possible, especially if you're using brown or red clay bodies. With white bodies you can get away with going a bit faster if needed.

If you need to slow it down at the beginning of the firing,  set the #2 timer to 6 hours, and just use the #1 switch to gradually turn up the heat, like go Min, 2, 4, Max at 1 1/2 hour increments, or set the time to 8 hours and do 2 hour increments. It's not so automatic that way, but it slows it down.