New Kiln Advice

[Skip]

I bought a used L&L e23-t kiln that has caused headaches from Day 1. I have replaced thermocouples, relays, and lots of elements. There have been a variety of issues but the most recent one is the kiln is taking about an hour extra  (firing slightly slower each time) each time to fire to cone 6 while slow glazing. I have verified that all the elements are heating. Instead of pouring more money into this kiln I am thinking about buying a new kiln. I was thinking about moving up to the e28t-3 but read an article about a known issue with firing this kiln to cone 6 on a 240v single phase set up. (I think II would need to add a sub panel if I move up to three phase which I would rather not do.) The issue was element life being greatly diminished even with quad elements.  I am convinced 3 inch walls are the way to go even if it means buying new kiln furniture if I go with another e23. Any thoughts would be greatly appreciated. If I buy a new kiln there is a friend of a friend with a high schooler looking to get into pottery. I would donate this kiln with fair warning to that family. Maybe they could buy all new electronics? I thought of doing this myself but would rather just start fresh.

[Bill Kielb]

I would definitely check all the basics with this kiln you already have, which means voltage drop during firing etc.....  the e23 t depending upon voltage and phase is an assortment of kw or available firing power. In the US (assuming you are here) you are most likely limited to 3 phase 208 service so your available power based on 3ph 208  will likely be 11000 w.  The 240 volt single phase version is 11500 w.  Definitely more power in the single phase model. Having additional phases is not magical, watts end up to be watts or to convert to btu multiply by 3.41. Anyway, the 240 volt model comes with more power so you will get more firings out of the single phase version.

Unfortunately wire size will be larger and I believe they call for a 60 amp breaker. I am confused about why your existing does not work well, it is a decent kiln and has a good power to internal square inch value. I can’t  help thinking that this kiln should work fine. If you could post as much information as practical I think you might get some good feedback. Just some things that strike me.

• How  many firings do your elements last?
• What resistance are they now?
• What is the operating voltage loaded?
• How long is too long for a firing?
• Any Pictures?

@neilestrick     distributes and services, I am sure he will weigh in here.

Thermal loss chart here: good for comparing available power and losses: https://hotkiln.com/sites/default/files/pdf/BTUS-Easy-Fire.pdf

 

[Skip]

Thanks for the input Bill. One element failed after 5 firings and another after 10. The other 4 elements are on firing 20 and are intact, but there is lots of element sag between the element holders where there is a gap either due to 16 years of shrinkage or more likely how the kiln was built. The elements fail where the sag occurs. In the two newer elements I stretched them as little as possible before installation. That seems to have helped with the sag, but only more firings will tell that for real. I am not handy enough to measure the resistance without electrocuting myself. I will add a photo of the serial plate since it may give some info. The cone 6 slow glaze time should be 7.53 hours, but I am running an hour longer. I do not mind the wait but slow times indicate a problem somewhere. 

[Bill Kielb]

Not many kilns I have come across can stay on the 7 hour schedule especially fully loaded unless they have very new elements. In addition do you preheat at all to dry things out. If so that time needs to be added. Pictures of the elements sagging would be great actually as well as the element holders usually make replacement easier and retain the elements pretty well. Did you replace all the elements and  the new ones failed within five firings and one failed within ten firings? If so I would definitely be curious to see a picture of these as well as the holders.

[neilestrick]

1 hour ago, Bill Kielb said:

Not many kilns I have come across can stay on the 7 hour schedule especially fully loaded unless they have very new elements.

This is most likely the issue with the firing time. The schedule the controller follows is not set in stone. There are many factors that affect firing time, and the controller allows for variation from the schedule to compensate for those factors. Dense loads, uneven loads, kiln setup, etc, can slow things down. 'Slow Glaze' in my big kiln is more like 10 hours. Here are some other things you can check:

1. Make sure your thermocouples are touching the ends of the protection tubes. If they're not all set the same, then the firing will slow down trying to even things out.

2. What is the thermocouple offset in the controller? It should be set at 18 degrees for all 3 thermocouples.

3. Have you gone through the controller to verify that the settings are correct? You never know what the previous owner did to it. It might be worth doing a factory reset as well. HERE is a link to the manual, look at page 33.

4. Like Bill said, measuring the voltage of the kiln under load would be good, to make sure you're not experiencing a voltage drop. How far from the breaker panel is the kiln?

5. Next time you fire, check the power cord and plug. Are they getting hot?

4 hours ago, Skip said:

there is lots of element sag between the element holders where there is a gap either due to 16 years of shrinkage or more likely how the kiln was built.

These kilns were all built the same way, and this is not a common problem. It's possible they shrunk, or it's also possible that someone replaced some holders with the wrong size. Please post some pictures of the areas with sag. Even some sag shouldn't account for elements failing. Is the sag right at the terminal brick, where the elements go through the wall? If needed, you can get new element holders. The current versions are a little bit different, but they will still fit in your bricks.

4 hours ago, Skip said:

I am not handy enough to measure the resistance without electrocuting myself.

Element resistance can be measured with the kiln unplugged. See HERE.

7 hours ago, Skip said:

 I was thinking about moving up to the e28t-3 but read an article about a known issue with firing this kiln to cone 6 on a 240v single phase set up. (I think II would need to add a sub panel if I move up to three phase which I would rather not do.)

Element life on the e28T-3 is about 85-100 firings instead of 135-150. With quad elements it should get it up to the 120+ range. The better option is to go with a more powerful kiln if you want a 10 cubic foot kiln. I assume this kiln is at your house? Chances are you won't be able to get 3 phase power at your house. But what you can do is move up to a larger breaker size and get a kiln that pulls more power on single phase service. If you go with the eQ2827-3 you'll have a cone 10 kiln with amazing element life, but you'll need an 80 amp breaker. That means pulling new wires as well as a new breaker.

I don't think replacing the old kiln will be necessary, though. It's a good kiln, we just need to figure out what's going on with the elements breaking.

[GEP]

For an L+L kiln that was born in January 2004, the correct TC Offset might be 50 instead of 18. L+L switched to a thinner TC protection tube around that time, so yours might be the older, thicker ones. Anyhow, I agree with @neilestrick that you should reset the kiln to the factory settings, in case the previous owner changed something that maybe worked for them but doesn’t work for you.

As for elements failing very young, I’m wondering how you are stacking the kiln? There was a time when I managed to kill two new-ish elements in a row. I had recently purchased cordierite plate setters, and was stacking them very close to the kiln wall. (I thought I was being space efficient, haha). After the second time it happened, I couldn’t deny that all that extra mass was somehow causing lots of stress on the elements in that one spot. By moving the stack about one inch closer to the center of the kiln, I never had that issue again. 

I agree with everyone above that an 8 or 9 hour firing with a full load is totally normal. 

[Skip]

Los of good advice, things to check, and things to work on. Thank you all so much. I will work on the things suggested and write again when I know more and have some pictures to share. The one thing I need to google or look in the links set is how to check the thermocouple offset. Again, thanks for all the helpful replies. I guess I am still committed to figuring this kiln out.

[Skip]

Hi GEP, your post popped up after I posted my most recent one. The elements have failed very close to my place setter posts!! This could be the problem with the failing elements. In loading my kiln the posts are very close to the side wall because of two plate stacks on the same shelf. So much to learn....

[Bill Kielb]

17 minutes ago, Skip said:

The elements have failed very close to my place setter posts!!

Always remember an inch or two away if possible. ANYTHING reflecting  all that heat right back at the elements especially in one small location is an element killer. This rule applies to all electric kilns.

[Skip]

This reply is long overdue, but I wanted to report back. Thanks to all of your great advice and a lot of help from Neil Estrick, my kiln is dialed in and firing perfectly. I really appreciate this community.

[Bill Kielb]

12 minutes ago, Skip said:

This reply is long overdue, but I wanted to report back. Thanks to all of your great advice and a lot of help from Neil Estrick, my kiln is dialed in and firing perfectly. I really appreciate this community.

Fantastic! Was  there one thing wrong, or a number of things? Might be good to know for anyone with the same issue in the future.

[Skip]

I fixed two potential issues. When I replaced an old element I twisted the wire counter- clockwise around the terminal instead of clockwise. I also had overstretched two elements such that there was sagging between some of my element holders, so I replaced those elements. Since I made those two changes the kiln has been performing perfectly.

[Mark C.]

Its always in the details