How Long Do Your Elements Last?

[neilestrick]

But why do they burn out so fast?? And sadly, I never fire a full load, as I don't make enough at one time. That is going to change, pronto!!!!

 

Thanks, Neil,

Nanc

 

Think of it this way- elements are metal, and most metals just don't hold up well at high temperatures. Many metals will melt at the temperatures we fire to, so the fact that they hold up at all is kind of amazing. Remember that all the colorants in our glazes are metals.....

[Guest JBaymore]

Mark, why is a Cone 6 electric firing a time issue? How do you fire? The people who I see firing in those brick ovens (salt firing?) take forever to fill them and then they take days to fire up and cool down? What is faster than electric, except raku? 

 

Large kilns technically are far more energy efficient than smaller kilns.  Every time you fire a periodic kiln (kilns that are heated up and then cooled off each cycle) you are heating the kiln refractories as well as the wares.  A huge portion of the energy used goes to this task.  A large kiln (on 100 CF one for example) encloses more volume with less wall area than the equivalent multiples of smaller ones (ten 10 cubic foot ones).

 

It is "nothing" to load and fire my gas kiln for bisques.  Far easier to load than a top loading electric.  Much bigger, and far better insulated.  Firing it is pretty much down to a science after all this time... so it is not really all that much more trouble than setting a controller if I am going to be around the studio anyway.  And I would never let the controller fire an electric kiln in my studio with out being around to make sure "all is well" anyway  (great way to lose a studio!).

 

FYI...... typically it takes me a solid week of labor to load my woodfired noborigama kiln.  2 days of firing.  3 days of cooling.  (I sleep 1 full day in there . )  BUT,....... there are a huge number of pieces in the kiln, and the average price point of the wares it contains is quite high.  Otherwise it would not really make sense.

 

best,

 

..................john

[Mark C.]

So is gas firing with propane?? And is it really a car kiln??? That is seriously creative!! Love it!!  I have to see pictures!!

Nanc

Nancy

My kilns are natural gas fired-you can see them in my Gallery-just click on my photo on this post.

Mark

[nancylee]

Mark,

After seeing your colors, I may be a convert!!! Oh, my, they are gorgeous!! I am a color nut, and they are indescribable.

 

I didn't see any car kilns in the pictures - do you really use a car???

[Chilly]

The "car" is a stack of kiln shelves that roll into the kiln, so you can load from all sides, one of the photo's shows it loaded ready to roll into the kiln. 

[bny]

My small test kiln has gotten only 6-8 firings to 2350F from each of two sets of elements. They don't burn out, but no longer develop sufficient heat to go beyond even 2200F. It is possible that I poisoned this kiln with zinc or with something in the element grooves.

 

I now have a second identical kiln that I am not taking above 2225F except for a couple initial tests at 2350F, and am not using with questionable materials. I have modified my body composition with enough 3124 frit to work well enough at 2225F.

[Chilly]

The rest of the class will be cross that we couldn't fire the kiln this week as we were waiting for the Kiln service/repair man, who hadn't arrived by the time we left at midday.  And, apparently there is nothing wrong with the elements in this kiln.

 

Doesn't explain why it can fire to cone 04 but not 6.  I'm waiting for them to get back to me on that one.

[Norm Stuart]

If the heating elements are fine, then one or more of the relays needs to be replaced.

apparently there is nothing wrong with the elements in this kiln.

 

Doesn't explain why it can fire to cone 04 but not 6.  I'm waiting for them to get back to me on that one.

[neilestrick]

The rest of the class will be cross that we couldn't fire the kiln this week as we were waiting for the Kiln service/repair man, who hadn't arrived by the time we left at midday.  And, apparently there is nothing wrong with the elements in this kiln.

 

Doesn't explain why it can fire to cone 04 but not 6.  I'm waiting for them to get back to me on that one.

 

Those elements look shot to me. See how they're all bunched up? They may not be broken, but they look worn enough that they won't produce enough heat to get to cone 6. Why are they so stretched out at the ends?

[Mark C.]

(Why are they so stretched out at the ends)

They used to be slinkys??and where pulled to much on the ends by kids.

Mark

[kdavitt]

I get maybe 200 or more firings out of my elements. When they sag, I pin them. My thermocouples go before my elements and in 6 years I've only replaced 2 relays on 3 kilns. I have heavy duty elements on my L&L E 28T 3 240 with over 300 firings - once or twice a week for the past 4 years. When a relay goes, I replace only that one but I make sure I have others on hand.

[glazenerd]

I fire to cone 6 oxidation: on rare occasions to cone 10. I am a big fan of APM elements: have them in all four of my kilns. I average around 350 firings on a set, and have gotten close to 400. Two of my four kilns were built with 25% more power than what is actually required, which puts less strain on the elements. My primary bisque kiln is a 16CF front loader: and I do not push it when firing. I do run cone 6 glaze cycles in it and push it on the front end until 1800F or so, then slow it back down to 180F to 2100F, and then down to 120F till 2190F with a hold. I am sure many would disagree with the cost of APM elements verses the benefit: but for me the proof is in my experiences. I replace elements once, for every four times you replace standard elements. The math is easy enough. I change my own elements and do my own kiln maintenance, including brick repair or wiring. Kilns are not that tough to work on; pretty basic machines for the most part.

Ne/rd

[Mark C.]

Nerd in your case with crystal firing amp elements and s thermocouples and zone control all make sense to me.

Since I only bisque in an electric and less than 10 times a year it makes no sense for me to have that set up.

If I worked with an electric as my main production tool I would do the same as you.

My elements tend to last over 15 years at cone 08 with light use

[neilestrick]

I fire to cone 6 oxidation: on rare occasions to cone 10. I am a big fan of APM elements: have them in all four of my kilns. I average around 350 firings on a set, and have gotten close to 400. Two of my four kilns were built with 25% more power than what is actually required, which puts less strain on the elements. My primary bisque kiln is a 16CF front loader: and I do not push it when firing. I do run cone 6 glaze cycles in it and push it on the front end until 1800F or so, then slow it back down to 180F to 2100F, and then down to 120F till 2190F with a hold. I am sure many would disagree with the cost of APM elements verses the benefit: but for me the proof is in my experiences. I replace elements once, for every four times you replace standard elements. The math is easy enough. I change my own elements and do my own kiln maintenance, including brick repair or wiring. Kilns are not that tough to work on; pretty basic machines for the most part.

Ne/rd

 

Nerd, you are exactly the type of person who needs APM elements. With the very specialized firing cycles and holds and such for the crystalline glazes, it makes sense. But for the typical kiln user they just aren't necessary. The other issue for most users is that APM elements aren't as durable when you get crud on them. A glaze glob can fry one out, and the savings is gone.

[glazenerd]

Neil:

I tend to get zoned in on my own experiences. I need reminded once in a while that what I do only makes up 0.05% of pottery. So I would have to agree with your balance to this topic. However, if I were a serious production potter relying on electric: they would still be on my list. Which brings me to question I have not seen addressed in here: do you think the element coatings are beneficial? I know a guy out in CA who swears they greatly increase his element life.

Nerd

 

Side note: I think Mark has it right by firing gas- if you are producing production pieces day in and day out.

[Min]

Another option that is rarely talked about is using a lower gauge wire. (we use 13 gauge), like Nerd said about APM elements this probably isn't for everyone but if your kiln has channels big enough to hold larger diameter elements and you don't mind winding them they do last a heck of a lot longer than the regular ones. 

[neilestrick]

Neil:

I tend to get zoned in on my own experiences. I need reminded once in a while that what I do only makes up 0.05% of pottery. So I would have to agree with your balance to this topic. However, if I were a serious production potter relying on electric: they would still be on my list. Which brings me to question I have not seen addressed in here: do you think the element coatings are beneficial? I know a guy out in CA who swears they greatly increase his element life.

Nerd

 

Side note: I think Mark has it right by firing gas- if you are producing production pieces day in and day out.

 

I think Min's suggestion of heavier gauge wire is probably the smartest way to go. We had a big discussion here a year or two ago about ITC and other coatings, and I have yet to see any definitive studies on element life that would justify the cost and added labor to apply it. Others also make claims about reduced firing costs, but I haven't seen any actual science on that. It's mostly like you said- 'I know a guy who swears by it'.   I can't recommend it to anyone until I see actual numbers, including labor costs. And if you put it on a new kiln you'll void your warranty unless it's applied by the factory. I think Axner used to offer ITC on their kilns, but I don't see that they do that any more. For me it falls into the category of top loading electric kilns with added fiber insulation -there's no actual evidence that it reduces firing costs or extends element life. It sounds like it would work, but I haven't seen any numbers from real world tests, just projected savings. Where I think ITC does work is as a brick coating that can harden soft brick and protect it from corrosive fumes.

[glazenerd]

I can attest to the brick coating: my 1.75CF test/small work kiln was ordered with coating on the lid and top rim. I can see noticeable differences, no signs of wear or the lid cracking. My 6.5CF top loader was ordered with 3" brick and 2" fiber" it is my primary crystalline kiln. I use to fire to a soft cone 10 before changing my glaze formula. I fired to 2295 with 20m hold, and then a total of 4 hours of ramp holds around 2000-2025F. The total firing costs were $5.45. So yes, I think the extra fiber does save money. However, it is not necessary unless you are firing these types of cycles.

Nerd

[Tim T]

A few things here.

 

I don't think the discussion so far has highlighted sufficiently the effect of firing temperatures on element life If you just bisque fire or do earthenware, you are working well below the melting point of the elements, and replacing kiln elements is a very rare occurence. Mine lasted a couple of years without needing replacing, and then I decided to play with oil spot glazes, so firing to 1290C and soaking for 2 or 3 hours, and now for this work I have to treat the elements as something needing replacing regularly (I haven't been organised enough to count the number of firings), as the temperature is much closer to the melting point of the wire.

 

I think you can look at firing times when deciding if elements need replacing, if you just look at the time when the firing cycle is on full power, and how long it takes to reach the top temperature.This is definitely better than visual inspection, and in my opinion better than measuring resistance, as the firing cycle is what affects the end result, not the resistance of the elements per se.

 

When I found that elements could wear out, I looked into it some more, and although my kiln could reach the 1300C claimed by the manufacturer (with newish elements), the element wire was quite thin, reducing cost but also reducing element life. Luckily the element slots are quite large, so I'm replacing the elements with a thicker wire that is longer (and so a larger diameter coil) to obtain the same resistance. This loads the wire a lot less, so I should get much longer element life, and hopefully also a reduced cost per firing - though even if it is about the same overall cost, it'll be worth it to save the hassle of replacing elements so often.

 

Another factor is that my kiln uses standard electro mechanical relays, which click in and out every 30 seconds or so. This means that the elements are always cooling down and heating up which stresses them more and shortens their life (Kanthal say as much as 20%). Replacing these relays with a solid state relay is my next upgrade job as, apart from being more reliable they can also cycle much more quickly, so the element temperature isn't jumping up and down so much, and the maximum element temperature is reduced. Again, if you are just firing at low temperatures, it probably isn't worth doing this, especially as it isn't just a simple plug-in replacement and some circuit changes are needed.

[neilestrick]

I think you can look at firing times when deciding if elements need replacing, if you just look at the time when the firing cycle is on full power, and how long it takes to reach the top temperature.This is definitely better than visual inspection, and in my opinion better than measuring resistance, as the firing cycle is what affects the end result, not the resistance of the elements per se.

 

How are you going to monitor how long the firing cycle is on full power, without constantly checking it? To me that defeats the purpose of having an automatic controller. And in a kiln with zone control, they are cycling even at high temperatures as they work to even out temperatures, so it's nearly impossible to tell when they're 'full on'. It's also possible that the total firing time won't increase much at all even though the elements are showing wear, as the controller will simply keep them on longer to maintain the schedule. It's often not until they elements get really bad that you start to see total firing times increase, and prior to that you've been wasting electricity with bad elements. Measuring element resistance is the best way to see the condition of wire.

[LHPottery]

I don’t have a comment but need some help on element replacement. My husband started replacing the elements in my Skutt kiln and didn’t realize that there were ones for too/bottom and center. So now that they are out of the bag is there any way to tell the difference?  I would hate to buy a new set. 

[Min]

28 minutes ago, LHPottery said:

I don’t have a comment but need some help on element replacement. My husband started replacing the elements in my Skutt kiln and didn’t realize that there were ones for too/bottom and center. So now that they are out of the bag is there any way to tell the difference?  I would hate to buy a new set. 

Use an Ohmmeter to measure the resistance of the elements.  Skutt chart showing element resistance for their kilns here and placement of which goes where here. At least one end of the element has to be disconnected from the rest of the kiln wiring.  Connect the meter to both ends of the element.

[LHPottery]

Thank you so much. You saved me some money!