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I have the very nice programmable controller on my 1027 Skutt.  It has only ever been fired to 06.  After 20 years and 400+ firings it still seems pretty consistent.  Will I see an increase in firing time as an indication of coil wear?  I did recently replace the thermocouple.

After it finishes my bisque ramp program, it flashes CMPT and a number.  The load that just finished is 9.5  Is this nine hours and 50 minutes or 9 hours thirty minutes?

Looking back over time, the firings have varied as much as 30 minutes.  What factors can cause variation in the same firing program? 

I load the kiln as tightly as possible every time.  I will stop and make a few pots if I need something to fill space.

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Density of load??

Proximity of density to 

Ambient temp?

Throwing in a Mark here...how the fish are biting...

What ramp is it losing time on?..or is each ramp just a bit out?

What type of controller?

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3 minutes ago, Babs said:

Density of load??

Proximity of density to 

Ambient temp?

Throwing in a Mark here...how the fish are biting...

What type of controller?

earth spin in regards to rotational axis-it can mess with you

Pressure drop

Brown outs

electron traction-often overlooked and misunderstood

 

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1 hour ago, CactusPots said:

I have the very nice programmable controller on my 1027 

After it finishes my bisque ramp program, it flashes CMPT and a number.  The load that just finished is 9.5  Is this nine hours and 50 minutes or 9 hours thirty minutes?

 

Weeeelllllllll.

For folk who oscillate between lbs, oz , miles,yds , feet and then  $ cents. Decimal pts can be very tricky.

Then the dot on line as opposed to mid line can be very tricky....

So depends whethet you come from counting your money or baking bread.

Go midway to 9hrs and 40 minutes:-))

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2 hours ago, CactusPots said:

I have the very nice programmable controller on my 1027 Skutt.  It has only ever been fired to 06.  After 20 years and 400+ firings it still seems pretty consistent.  Will I see an increase in firing time as an indication of coil wear?  I did recently replace the thermocouple.

After it finishes my bisque ramp program, it flashes CMPT and a number.  The load that just finished is 9.5  Is this nine hours and 50 minutes or 9 hours thirty minutes?

Looking back over time, the firings have varied as much as 30 minutes.  What factors can cause variation in the same firing program? 

I load the kiln as tightly as possible every time.  I will stop and make a few pots if I need something to fill space.

To answer your questions

Firing time and wear.
Yes firing time will increase as elements wear. At cone 06, they will last many many firings. You may actually get to a point where you want to change them just because they have enlarged so much and embrittlement  so much it becomes difficult to remove them. a 10% change in element resistance from new is often enough to cause issues with glaze firings to cone 6. Since you fire to 06, they may be fine until  the element value changes by 15-20%. Again getting them out of the grooves at this point may be difficult.

Time display
9.50 on a typical controller stands for 9 hours 50 minutes.

Firing time loading

Firing time varies by load. The greater the density, the higher the time. If you ever load a kiln full of flat plates, the shelving and amount of plates basically by weight will have a big influence on the firing time. Of course normal element wear will slowly make your firing times gradually increase On average  as the elements lose power.
 

 

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Come on Bill -This theory was my thesis back in the day                             ---------------------------------------------------  in Art School

(Electron traction-often overlooked and misunderstood)

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6 hours ago, Mark C. said:

Come on Bill -This theory was my thesis back in the day                             ---------------------------------------------------  in Art School

(Electron traction-often overlooked and misunderstood)

Engineering had a similar  bout with cold fusion, an impending ice age and my favorite, the  original food pyramid! It was a quarky  time I might add.

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In a digital kiln, firing time will not increase until the elements have worn enough that they're no longer able to keep up with the firing schedule. Up to that point, the kiln just keeps them on longer as it cycles the relays to get the heat it needs. Checking the element resistance with a meter is the most accurate way to tell if the elements need replacing. When the resistance is 10% off, replace them.

 

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1 hour ago, neilestrick said:

In a digital kiln, firing time will not increase until the elements have worn enough that they're no longer able to keep up with the firing schedule. Up to that point, the kiln just keeps them on longer as it cycles the relays to get the heat it needs. Checking the element resistance with a meter is the most accurate way to tell if the elements need replacing. When the resistance is 10% off, replace them.

 

10% off new, I expect.  Get that info from handbook or website?

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          http://hotkiln.com/sites/default/files/pdf/troubleshoot-element_0.pdf

"If the readings on your elements are more than 10% over the factory resistance values the kiln will climb in temperature very slowly and may not reach maximum temperature . "

          https://hotkilns.com/checking-elements

"A very general rule of thumb is that most people will typically begin to notice some slowdown once you've lost more than 10% of your power."

 

Tip o' th' iceberg, just!

 

Keep detailed notes - loading, times, temps, meter readings, etc.

Happy Mother's Day!

 

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Since I'm not going above 06 and firing on a programmed schedule, the kiln won't take longer or be unable to reach temperature, but should be using more power than new at some point.  Right?

Anyone have an expectation for the life span under these conditions?  

 

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I used my skutt 1227 for over 20 years firing to 08 only without new elements-Maybe 8-16 fires per year -as its not my main bisque kiln. Then one element burned out and I replaced them all. Before that its was taking longer to get to temp (costing more) Now its  firing quicker again. I would have to look at my log to get that number of firings-my guess is over 250-300 at least

It all depends on how many firings you have on it-do you log them so you know that number?

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1 hour ago, CactusPots said:

Since I'm not going above 06 and firing on a programmed schedule, the kiln won't take longer or be unable to reach temperature, but should be using more power than new at some point.  Right?

Anyone have an expectation for the life span under these conditions?  

 

You will only use more energy as your elements degrade to a point where your kiln has insufficient power to maintain the firing rate within reason. At that point your firing times will extend and your excess energy will be the additional losses through the shell for the additional time it fires to make temperature. When the time to reach temp becomes excessive the kiln begins to overfire as heatwork starts to Influence the firing.

For folks who fire very low all the time their cone 10 rated kiln often has enough excess power to continue firing and making temperature within a reasonable time until their elements degrade by 15% or more.  How many firings is speculation. One thing I do know, for these situations the elements begin to get very hard to remove from the grooves. They enlarge and come out in bits and pieces even though they still have enough power to make it to  a low cone temp in reasonable time.

The 10% rule exists because most of today’s cone 10 kilns rarely fire on schedule even brand new at cone 6.  They are marginally powered to start, for a real reason though. Most brand new cone 10 kilns fired to cone 6  do not have enough power to execute a fast four to five hour glaze schedule with a tightly loaded kiln. It’s just a function of power designed into the kiln as a result of electric commonly available and shell insulation of the kiln versus construction methods and cost.

Put more wattage in, more firings per element change but Bigger electric service to the kiln is needed and it’s a higher cost to construct. Insulate better then less wattage needed or more firings on a set of elements to reach a given temperature and yes more money to produce.

So how many Firings  for a lowfire kiln. My suggestion when the elements are too brittle to remove without cussing up a storm because they are so brittle only 2” come out at a time or, when your firing times for a typical load start extending so far that you begin firing an additional cone or two. Probably a few hundred firings.

At cone 6 Brand new kiln firing times will often vary by 15 minutes or more, especially larger kilns depending upon the amount of wares being fired which only adds to the confusion of course. If you graph a brand new kiln, surprisingly you will most often find that it has trouble keeping up with a very fast schedule especially tightly loaded.

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2 hours ago, CactusPots said:

Since I'm not going above 06 and firing on a programmed schedule, the kiln won't take longer or be unable to reach temperature, but should be using more power than new at some point.  Right?

Anyone have an expectation for the life span under these conditions?  

 

Firing at cone 06 you probably won't see any slowdown of the firing as the elements age, until they're really really bad. And like Bill said, it gets to be more difficult to get them out, and you're more likely to damage the bricks because the elements distort and often the coils expand as they age. After the 10% change you'll be using a lot more energy. I recently did a test in my smaller kiln, and fired the elements until they would no longer reach cone 6. At that point I was using twice the energy as new elements.

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2 hours ago, Mark C. said:

I used my skutt 1227 for over 20 years firing to 08 only without new elements-Maybe 8-16 fires per year -as its not my main bisque kiln. Then one element burned out and I replaced them all. Before that its was taking longer to get to temp (costing more) Now its  firing quicker again. I would have to look at my log to get that number of firings-my guess is over 250-300 at least

It all depends on how many firings you have on it-do you log them so you know that number?

Don't have them all logged, but I have fired pretty regularly 3 loads per year in my gas kiln.  The average number of electric bisque per gas load is about 7. 

3 x 7 = 21 x (20 years)= around 400

1227 is larger than my 1027 by about 30%, I think.  If it's the same amperage (60), then it's working harder, right?

I just don't know if this is something to pursue or not.  It seems to be working fine, but I am a believer in regular maintenance where necessary.  If I could find a test procedure, I'd probably do it.

My electric kiln is better insulated than standard, as I run a 4" fiber blanket on the top.  Cool to 200 before removing.

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1 hour ago, CactusPots said:

Don't have them all logged, but I have fired pretty regularly 3 loads per year in my gas kiln.  The average number of electric bisque per gas load is about 7. 

3 x 7 = 21 x (20 years)= around 400

1227 is larger than my 1027 by about 30%, I think.  If it's the same amperage (60), then it's working harder, right?

I just don't know if this is something to pursue or not.  It seems to be working fine, but I am a believer in regular maintenance where necessary.  If I could find a test procedure, I'd probably do it.

My electric kiln is better insulated than standard, as I run a 4" fiber blanket on the top.  Cool to 200 before removing.

10% is probably a smart point for you as well so it’s pretty simple.  If your element new is 10 ohms then once it reaches 10% more or 1.10 X 10 = 11 ohms it’s time to consider replacement. Since you are always firing low, degrading by 10% will still take a few hundred firings. Certainly more firings than the typical cone 6, 100-150 firings. Min posted the chart, so easy to verify from time to time.
 

Your fiber does help! Think of it this way, if your kiln new  Is 10,000 watts, that is the amount of heat available to you (basically 34100 btuh) when these elements wear 10% they increase in resistance by 10% which actually means 10% less watts or now 9900 watts available. It now takes longer to heat your kiln and the longer it takes the more the kiln also loses heat through the shell. Sometimes these are referred to as standby losses. As Neil said, at the top  Kiln temperatures or end of firing, the rate of heat loss is large so this can amount to a significant increase in electricity use.

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1 hour ago, CactusPots said:

Don't have them all logged, but I have fired pretty regularly 3 loads per year in my gas kiln.  The average number of electric bisque per gas load is about 7. 

Why not just bisque in the gas kiln?

Only running to low fire temps, elements can definitely last 400 firings. Best to start putting a meter on them every 25-50 firings starting at 250 though to verify the resistance.

1027 is 7 cubic feet, 1227 is 10 cubic feet, so about 40% bigger. Yes, a 1227 that pulls the same wattage as a 1027 will work harder to heat it up. With bisque, though, the firing cost per pot will likely still be lower in the bigger kiln.

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I bisque in my gas kiln at least 98% of all work. Cheaper to fire -more efficient to load .I only use the electric for extra bisque to make one car kiln glaze fire into two with a single gas bisque and one electric. I can also bisque wet pots if needed fast as the control (heat rise) is greater in the electric.

I have found a few gas potters use an eelctric thinking its easier-One of our local guys did this for years until I point out the cost-he gave up the electric bisquing  when He found out how much its was costing him over the gas kiln bisquing

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The "issue" with the wattage being the same in both the 7 cu.ft. 1027 and the 10 cu.ft. 1227 is that the electric code allows plugs only up to 60 amp circuits. With the 125% rule, the most amperage a kiln can pull on the 60A circuit is 48A. So, to keep the 1227 as a plug-in kiln, it can only pull 48A, or the same wattage as the smaller 1027, which then limits the top temperature to cone 8 (optimal, expect cone 6 is regular use). If you want enough wattage/amps in the larger kiln to go to cone 10, then you need to either hard wire it to an 80+ amp circuit or go to a commercial location where you can get 3-phase service.

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1 hour ago, Dick White said:

The "issue" with the wattage being the same in both the 7 cu.ft. 1027 and the 10 cu.ft. 1227 is that the electric code allows plugs only up to 60 amp circuits. With the 125% rule, the most amperage a kiln can pull on the 60A circuit is 48A. So, to keep the 1227 as a plug-in kiln, it can only pull 48A, or the same wattage as the smaller 1027, which then limits the top temperature to cone 8 (optimal, expect cone 6 is regular use). If you want enough wattage/amps in the larger kiln to go to cone 10, then you need to either hard wire it to an 80+ amp circuit or go to a commercial location where you can get 3-phase service.

I hard wired my 1227-better connections and less oxidation/corrosion issues as Dick pointed 

I like hard wiring over plugs on any high amp device

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5 hours ago, neilestrick said:

Why not just bisque in the gas kiln?

Only running to low fire temps, elements can definitely last 400 firings. Best to start putting a meter on them every 25-50 firings starting at 250 though to verify the resistance.

1027 is 7 cubic feet, 1227 is 10 cubic feet, so about 40% bigger. Yes, a 1227 that pulls the same wattage as a 1027 will work harder to heat it up. With bisque, though, the firing cost per pot will likely still be lower in the bigger kiln.

I don't bisque in the gas kiln because I  haven't been able to fire gas  as evenly as the electric at low temps. Also the  convenience of a  of a schedule over night.    I figured the load of regular bisque firings into the configuration of the solar panels on the house.  I get a LOT of sun where I live.  My best guess of cost for 1 load in the electric kiln was about $15.  So 7 x 15 = 105  Propane kiln is about 35 gallons at $4 = 140 to cone 10

But like I said, it's already paid for.

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Since I'm working on a 9,600 watt solar array  right now myself so I get why you like that electric and that low cost in power. Be there soon myself. I have natural gas which is way cheaper that propane. Also for me pushing 35 cubic feet of  bisque ware thru an electric kiln (even at 10 cubic feet-1227)  each cycle is to labor intensive.

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13 hours ago, CactusPots said:

I don't bisque in the gas kiln because I  haven't been able to fire gas  as evenly as the electric at low temps. Also the  convenience of a  of a schedule over night.    I figured the load of regular bisque firings into the configuration of the solar panels on the house.  I get a LOT of sun where I live.  My best guess of cost for 1 load in the electric kiln was about $15.  So 7 x 15 = 105  Propane kiln is about 35 gallons at $4 = 140 to cone 10

But like I said, it's already paid for.

A bisque firing in a gas kiln will cost less than half the cost of firing to cone 10. Most estimates I've seen say that firing to cone 6 uses about the same amount of gas as firing from cone 6 to cone 10. You an probably bisque for 1/4 the cost of a cone 10 firing or less.

I'd love to have solar panels on my shop.

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