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GoodKarma

Kiln never got to cone 6, should I wait longer?

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Hello, I just fired my first load in my new kiln! Very exciting and nerve wrecking!! I have a  Skutt Model LT-3K (manual).  I had it on LOW for 3 hours, MED for 3 hours, then I switched it to HIGH... and it ran for 5 hours... it was 2:00 in the morning at this point, and I couldn't see the darn cone, so I worried the kiln sitter was messed up, and it was taking too long and over firing. I turned it off, and 12 hours later opened the kiln to see that both the cone AND the kiln sitter bar hadn't moved AT ALL.  Should it take that long, or was I just being paranoid?  It's such a small kiln, I wouldn't think it would take over 11 hours to reach cone 6.  I had one shelf on the bottom of the kiln, and one half shelf, 10 pots total. Shelves are 13".   I had the lid closed & the top plug out.

The manual says put it on LOW for 2-3 hours, MED for 2-3 hours, then HIGH for 2-3 hours until it reaches temp... but 5+ hours on HIGH seemed too much?

Most of the pots were crazed... guess I'll have to re-glaze and re-fire no matter what, but I need to find out how long it should take, rather than running the kiln for unknown hours.

Thanks for any help/ideas!

KILN.JPG

Edited by GoodKarma

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Is this the load you had? If this is the load, you really did not fire too long, as such a loosely packed kilns does not conduct enough heat to reach temperature. At the same time, I do not fire long at all on either low or medium, usually firing right after glazing with lid open part way and bottom two switches on low for an hour, then I close up the lid leaving the peeps out, turning switches to medium for an hour, close her up and switch to high on all switches. Usually fires 6-7 hrs to reach ^6. However, I always pack a full load as radiant heat transfer is the most efficient way of evenly heating an electric kiln, pots on the outside heat up the pots on the inside, when the kiln is half empty not radiant heat.  Electric kilns do not have air currents to carry heat to all parts of the kiln.

 

best,

Pres

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Lt-3k is the model of the kiln sitter, not of the kiln itself.

Is it supposed to reach cone 6? You said it's new, does that mean new to you? Could the elements be in used condition?  Generally problems reaching temperature are due to worn elements

My kiln is 18x23 inches inside and fires to cone 6 in 5 hours on the fast glaze setting (slow for the first and last bits, "high" for the middle part).

Edited by liambesaw

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Yes, this was the load.... Brand new from the factory. It's rated to cone 8, but my clay & glaze is rated for cone 6.... kiln sitter bar & witness cone are both 6.  It came with one full shelf & one half shelf... and I read that it was best to NOT load on the kiln floor, so the full shelf is at the bottom (on 1" stilts).

Edited by GoodKarma

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So this is a 120v kiln I take it. I don't know if those take longer to heat up than a 240 of the same size.  Is the circuit using a 25 amp breaker and 10 gauge wire?  That's what Skutt recommends for it.  

 

And yeah just let it run til it drops, until you know how long it will take you'll just have to keep an eye on it.

Edited by liambesaw

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All electric should be fine, I had to have an electrician put in a 50 amp breaker because it kept tripping the breaker on the 30 amp it was on. (The kiln says 20 amp, but the label on the kiln sitter says 50 amp)

Edited by GoodKarma

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15 minutes ago, GoodKarma said:

All electric should be fine, I had to have an electrician put in a 50 amp breaker because it kept tripping the breaker on the 30 amp it was on. (The kiln says 20 amp, but the label on the kiln sitter says 50 amp)

Yikes, the 50 amp label on the kilnsitter just means it can be used on kilns up to 50amps, it's not how much it pulls.  It needs to go onto a 25 or 30 amp circuit with appropriately sized wire.  Putting a 20 amp appliance on a 50 amp breaker is a recipe for a house fire, especially if that 20 amp appliance has been tripping a 30 amp breaker!

I'd maybe find a different electrician if that was his solution, always follow the manufacturers specifications!

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Yikes indeed! Well... he installed a new line solely for the kiln, straight from the breaker (30 amp) and when I put it on high, it tripped the breaker.   He found no issues, so he said it must be the kiln... he took another look at the kiln, and he saw the kiln sitter label, (which said 50 amp). So he changed the breaker & wire to 50 amp.   It worked, so I thought that solved the problem, but I guess finding another electrician and getting a second opinion is in order. Too bad I already paid this guy and ended up with a hazard. :(

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This is a kiln that requires a neutral wire and a ground. It is 3600 watts and should easily work on a 30 amp 2 pole 240 volt breaker. I would make sure this is wired correctly as it is a bit unusual and wired incorrectly will have unexpected results. Changing a 30 amp breaker to a 50 amp while leaving 30 amp wiring in place is a fundamental flawed idea in my opinion.  I would have this double checked before operating this kiln again.

A36AB801-29E5-40DB-B053-22AB6DDFA605.png.aff5098c89a72941583f847b84ba247c.png

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Hi Good!

If/when you look at getting more shelving, may I recommend half shelves - more flexibility? Staggering (different heights) the upper levels gives me more even heating; my top level was running too cool with the shelves levelled up.

Other suggestion I'd like to offer: monitor firing temperature, which you can do if your cone packs are visible through the peep holes (wear appropriate eye protection!!). I also use a pyrometer, which is very handy for slowing down through critical temperature ranges, note taking, etc.

For glaze firing, I bump up to about 200F the night before, turn all off, then go straight to High the next morning - everything is still warm, and also bone dry; no Low or Medium until the brief hold after reaching peak temp. Bisque fire requires much more attention...

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UPDATE!  I called  Skutt, they said it has to be the wiring.  I called my electrician... the wiring was correct.  I took the bottom shelf out of the kiln to inspect it.... guess what I found!?  A HOLE in the wall where the element comes into the kiln (behind the kiln sitter box).  I called Skutt again, I sent them pictures and all my contact info... hopefully they can help me out with this... he said the elements must have been touching something metal somewhere.  I live in the middle of nowhere New Mexico (between Albuquerque N.M & El Paso T.X.) so I'm not sure if they can get a kiln tech out here or not...

kiln element 2.JPG

KILN HOLE 2.JPG

KILN HOLE 3.JPG

KILN HOLE.JPG

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Looks like you found the issue, now why would a new element melt in the middle of its span. I would still be concerned how it is wired. Especially since the 30 amp breaker was changed to a fifty. Do you have any pictures of the breaker and where the wires connect inside the kiln?

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Sometimes elements just decide to melt out. Could be something was on it like a piece of glaze or such, but sometimes they just seem to go. It's also possible that a pin right there was touching a screw coming in from the outside, which would explain the breaker flipping and the element frying. It failed hard, and took a little bit of the brick with it. When you replace the element, you can probably just dig out any melted stuff, and make sure you pin it right there. You probably won't need to replace the brick unless you have to dig out a really big chunk.

As for the wiring: The kiln pulls 20 amps, correct? Code requires that it be on a breaker that is rated 25% higher but no more that 50% higher, so it should be on a 25 or 30 amp breaker. The wires feeding the outlet should be rated for at least 30 amps, which means at least 10 gauge wire. To use the 50 amp breaker, the wires would need to be at least 6 gauge, which is much larger than the 10 gauge. If the electrician used 10 gauge wire and a 50 amp breaker, he doesn't know what he's doing, and has put you in a dangerous situation because the 10 gauge wires can overheat and melt and cause a fire if 50 amps go through them. Plus a 50 amp breaker on a 20 amp kiln  is not up to code, and again the electrician doesn't know what he's doing. The solution to a tripping breaker is not a higher breaker. There's something causing it to trip that must be fixed. You found the problem which is good, but you should either have another electrician in to make everything correct withe wiring and breaker, or have the original electrician in to fix everything and get it up to code at no cost to you.

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This is exactly mid span of the bottom element and in the loaded picture above there is clearly nothing touching or near this. So now I am wondering if the 120v element was installed by mistake at the factory because the circuit diagram indicates it should be at the top. This appears to have melted midspan from overload so that is a possibility.

Very odd that this could melt; however the tripped 30 amp breaker likely was telling us to stop and figure out why. Running it with a 50 amp without troubleshooting could negate the warranty.

However this turns out, I would be disappointed in the change from 30 amps to 50 amps. It will likely cause issues with the warranty.

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25 minutes ago, liambesaw said:

The technical term is Sizzle Sauce.  It's only happy juice if you're speaking from an appliances perspective.  Angry pixies if you're Canadian

Sizzle Sauce sounds like the name for any drool that escapes, after you received a zap.

Do Canadians blame pixies for their woes?

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