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Kiln Circuit Design.

kiln electronic design wire fire

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#1 High Bridge Pottery

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Posted 04 February 2014 - 08:52 AM

Hello, I am still having big problems with the kiln I own. Long story short, it has been broken now for about 2-3 months. First off one of the relays fried itself. So I replace that. Then it fired twice, one bisque and a cone 9-10 glaze.

After that it broke again with the controller spitting out an Error F1. No manuals or manufacturers known for either the kiln or programer. Looked again at the wiring and the wire attached to the top relay has fried, half of the coating had burnt off and it was getting very hot. This is probably what broke the relay in the first place but I didn't notice. It is on the wire where the electricity exits the elements. The top circuit has 6 elements wired in parallel pairs.

 

Replaced the wire and it was still getting very hot. This time where the elements come out the kiln it was starting to glow and spark which I had never noticed before. So it is not the relay or the wire that is causing the problem it must be the elements right? 

 

The problem is I know little about electronics and the guy who I share the studio with knows even less.

 

He had an electrician come over to look at the kiln. Problem was I wasn't there and he doesn't really know what the electrician has done. I am sure he is good at his job but I have no idea what he has done with the wiring. I mean it looks like he has changed the bottom into a series circuit and the top, well I have no idea how it is meant to work.

 

Here is my attempt at working out how he has wired the top elements, to me this makes no sense but please correct me if I am wrong. They are two drawing of the same circuit.

 

Attached File  FxCam_1391519887782.jpg   43.24KB   1 downloads

 

I spent most of yesterday trying to work out and design a circuit that will work. The elements look ok to me but maybe they are causing the problem. I just don't know. I know one guy who fixes kilns and replaces elements but he is very slow at getting round to doing anything :(

 

I took some amp and resistance readings from the kiln to try and work out what the overall resistance is. The kiln consists of two relays, the bottom one has four elements wired in parallel pairs and the top 6. 10 elements in total. Is this the right way to have it wired up? The power comes in bottom left and right and out the middle pins.

 

Attached File  FxCam_1391519270446.jpg   40.06KB   1 downloads

 

So I started with what the ideal circuit should be. I have 240v supply at 32amp, which means my overall resistance should be 7.5ohm.

 

Overall the top elements have resistance of 11.6 and the bottom elements a resistance of 10 (one top element has 17ohm and one bottom elements has 10ohm). This makes the overall resistance of the circuit 5.4ohm as the elements are wired up in parallel. 

 

Ok so that is the resistance for the circuit but just taking in elements resistance values so probably not that correct. If I use the amp reading that I am getting going to and from the relays I end up with a value of 7.07ohm for the overall resistance which is a lot closer to my ideal value.

 

After all of that I am not really any closer. The top relay has an amp reading of 18.5 and the bottom relay 15.5. I think I worked out that if my ideal resistance was 7.5 then I should have an amp reading of 18.75 for the top and 12.5 for the bottom. I am a bit confused on reading back my working out now haha.

 

I have just noticed that 18.5+15.5 = 34 but I am sure we have a 32amp breaker which doesn't make any sense either.

 

So none of the values seem that wrong although I may have completely done the maths wrong, I mean the bottom seems to have too many amps but it is not the bottom that is broken. Those elements seem to be working fine. The top where the electricity exits the elements to go to the relay is where the problem is happening.

 

Anyway if you have read this far, thank you :D I don't know if anybody can help but could you at least tell me if the parallel pairs is the correct way for elements to be wired up? Can anybody spot where the fault may lie? I don't want to replace the elements if that is not going to help either! I have just been slowly replacing and breaking more things.



#2 neilestrick

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Posted 04 February 2014 - 09:22 AM

Some kilns have elements wired in parallel, others have elements wired in series. Some put one element on a relay, some put 2 or 3 or 4 on a relay. Some do a combination. You need to get a wiring diagram from the manufacturer.


Neil Estrick
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Owner, Neil Estrick Gallery, LLC
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#3 Arnold Howard

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Posted 04 February 2014 - 10:12 AM

A loose wire connected to a relay will overheat and burn out, causing the relay to fail. When that happens, replace not only the relay but the wires that are connected to it, or at least the wire terminals. This is because once a push-on terminal becomes too hot, the terminal will lose its spring tension, resulting in a loose connection. That, in turn, will cause the new relay to fail prematurely, too.

 

From your description, an element connector is loose. That will cause the element connector to glow pink. I would replace the element connector. Make sure the new connector is tight.

 

I would not redesign the wiring in the switch box. It would be far easier to obtain the original wiring diagram and to use that as a guide. You might be able to identify the kiln from the electrical data plate or by posting a picture of your kiln.

 

Sincerely,

 

Arnold Howard

Paragon Industries, L.P., Mesquite, Texas USA

ahoward@paragonweb.com / www.paragonweb.com

 



#4 High Bridge Pottery

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Posted 06 February 2014 - 01:10 PM

The big problem is that there is no manual or anything like that with the kiln. It was made by a man who I don't know. Had a good kiln technical man come over and he said all the wiring is fine so I think it is just a connector/element problem.

 

Long story short, I think I might have found the problem area. Two elements were coming out and connecting to one connector. This seems to be what was making it really hot as once I changed it to one elements on each connector the wires did not heat up nearly as much. Bit of a patch job so need to buy all new connectors and do it properly this weekend.

 

The bottom elements do have a similar two elements > one connector but it doesn't seem to have the same problems. There are less amps going through the bottom circuit so I guess it just doesn't have enough power to cause the problems.

 

Hopefully it will be finally fixed by next weekend. At least now I know what I am doing with kiln electronics :unsure: , it has been an interesting few months starting from nothing but I enjoyed it :D (slightly)

 

Thank you for the help.



#5 Chilly

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Posted 06 February 2014 - 01:33 PM

Hooray, nice to hear you've solved it.


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#6 High Bridge Pottery

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Posted 06 February 2014 - 01:42 PM

Thanks Chilly, all it took was me buying a lot of clay to get the guy into my studio! He was a nice guy and gave me an hour of his time for free.

 

Turns out I was right in my thinking, just nice to have it confirmed by somebody who knows more  :D made me feel a bit more confident in my own problem solving skills.

 

After the big one is fixed I have a broken kiln that I picked up for £60 to work on. I couldn't help myself as for the bricks and structure alone it seemed to be a bargain. Going to be my little test kiln once it is up and running.







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