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Scott G

Kiln help -Seal or Insulate kiln pro/con? Bought and installing a dowdraft vent

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Hello community, first post, looking for help.  Got an old Skutt kilnsetter model 231 (electric) kiln donated to me.  Specs for the kiln are single phase 240volt pulling 47AMP.  The electricians who ran the line apparently only installed 40amp breakers which I am working to fix, the kiln constantly trips the breaker when going to high on all 3 knobs.  

I just bought the envirovent downdraft vent kit for the kiln, but since this thing is older than I am, I am worried it will be pulling air in from all the gaps in each section - (base to section 1 aka low section, section 1-2, 2-3, and 3-lid).

I blame this intelligent community for my paranoia because until recently I had been keeping only 1 peep hole open on firings but a recent glazed bisque firing yielded a bunch of what looked like burnt pieces and it was devastating.  There was post about oxidation kilns and how I should be firing greenware with all peep holes open and the lid propped by ceramic fiber blanket until I reach 1700F.  This took a lot longer, especially with me running down to breaker to reset (wrong amperage breaker, will fix) but in order to increase efficiency I want to seal each gap with blanket on the outside, was thinking of buying more fiber blanket, cutting strips 3-4 inches wide, and wrapping around the kiln so the downdraft vent can successfully pull air in through the top. Or wrapping around most of outside except manual dial area.  I don't have actual peep hole plugs so I made some out of clay, which I would keep in place and figure out some way to insulate those with blanket too.

Is this necessary?  I read some forum where there was a comment made about the blanket causing issues for the steel wrapping around the firebrick which I would be covering and I dont want to cause more issues.  I also have some kiln cement I could mix in and attempt to spackle in each gap but I already know this wont stay, seal, or work well.  chemical hazard with the kiln cement as well, not ideal.

The kiln and its firebrick is in ok condition, I think the kiln is 30 years old, but the small gaps will very likely reduce effectiveness of the drilled holes.  I'm worried I'll do all this work installing the vent, and when I hold a flame to the lid holes I drilled, it won't suck it in much.  Also, being an engineer I like the idea of insulating the outside of the kiln if there aren't many risks associated with this.  

 

THANK YOU IN ADVANCE FOR YOUR THOUGHTS AND COMMENTS!

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I would just buy so spy plug peeps they do not cost much-even on e-bay or at the very least make your own front soft brick with saw and sure form file-they actually work better than the slip cast ones.

the fiber will make jacket rust faster than usual -I think you are overthinking this.Unless the gaps are large. If its just a glow at ring connection let it be.

As to the 47 amps that kiln needs a # 6 wire to it and a 50 or 60 amp breaker. If your wire is a #8 then 40 amp breaker is what that wire size needs its the size of the wire determining breaker size. DO not put a 50 amp or 60 amp breaker on a #8 wire only a #6 wire

So find out what size wire you have going to kiln outlet or hardwiring.

do not spackle the bricks with cement as it will just flake off and break out more brick as it does not expand and contract like soft bricks in kiln

Show us a photo pf bricks if you think they are large gaps so we can see what you talking about

My old  231 is much older than yours and would work fine if I used it(I have 1227 now that I use) Old means nothing its condition not age

The big deal is the bricks are only 2.5 inch vs 3 inch thick and thats the difference. If you do not care about longevity than go ahead and wrap the kiln but just be aware that the jacket will fail way before its time-maybe you do not care as it was free. Do not wrap the controls boxes (red) as that will overheat them and destroy the guts (not good)

Just make sure you next kiln is a 3 inch brick one for cone 5 work

One last note close up the kiln when firing bisque after  your vent is installed-I bisques without a vent with the peeps always in and the lid cracked open a few inches until about 800 degrees then close it up. I use porcelain clay and do not suffer from carbon issues.

 

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Thank you Mark. Great info thanks for sharing.  I had an electrician run the wiring and I told and showed them the Kiln with the specs on it so they knew they're supposed to put in at least 50 amp breakers for it.  

Since you were so helpful, how much difference can I really expect with purchased peephole plugs versus ones that I have custom fit and subsequently semi fired from previous uses? See pic. 

 

Thanks 

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I wouldn't wrap kiln in ceramic blanket.

It can make stuff ,not meant to, overheat. I melted a peep cover doing that. Another potter melted pyrometer/thermocouple connection.

Car.fibre gets flaky and brittle and v. Dangerous if inhaled.

"Glazed bisque"???

Just my thoughts

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No need to do anything to the kiln to further insulate or reduce gaps.  All that will cause more problems. Just leave it alone. As for your vent, I would first try it without any holes in the lid. There are generally enough gaps that the holes in the lids are unnecessary, especially with old kiln. If you find the vent isn't doing its job effectively, then add the holes in the lid. Keep all the peep holes plugged, They need to fit well, probably better than your homemade plugs. 6 peeps with lots of leaks will mess with the vent performance.

Your kiln needs to be on a 60 amp breaker, with #6 wire. NOT a 50 amp breaker. That's to meet code, which requires a breaker that is 25% greater than the draw of the kiln.

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The main difference is that you can pull out a soft brick spy plug with an ungloved hand vs a hot clay or slip cast plug with a glove .

Yours looks a bit sloppy (not a perfect circle)to me and a soft brick cone would be tighter and run cooler while taking it in or out.

If you make one or three out of a single k23 soft brick saw the rough shape and finish with rough sandpaper. like 80 grit or rougher.

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9 minutes ago, Mark C. said:

The main difference is that you can pull out a soft brick spy plug with an ungloved hand vs a hot clay or slip cast plug with a glove .

Yours looks a bit sloppy (not a perfect circle)to me and a soft brick cone would be tighter and run cooler while taking it in or out.

If you make one or three out of a single k23 soft brick saw the rough shape and finish with rough sandpaper. like 80 grit or rougher.

Soft brick cheaper than your standard peephole bung as well.  I use a 3 incher for my peephole and it's really nice to be able to pull it out to check my cones and not have to go grab some gloves.

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