HELPLESS WITH THE KILN COTROLLER

[Havi]

Hi everybody,
Just to indicate how stressed I am, I would say that it is after midnight here, and I am completely lost with my kiln[?] OR controller [?] or both.
Jen Ken 24" squarish, Orton controller. Set the kiln for a firing which was supposed to go as high as full fuse 815 centigrade, yours 1499
Went away for couple of hours to find the kiln with the anouncement
HtdE - which means High temprature deviation Alarm.

I saw that the temp was still below maximum, so decided to wait and see what is happenning later. Tried to abort -the kiln said "idle" but kept raising the temp. So I turned it off - even though I have something there that needs real annealing..........
Went to check on it 10 minutes later -
Surprisingly, it kept raising the temp. even though it was turned off!!!

So I decided to unplug it out of fear that God knows what will happen. At that point the temp. was 840 C, yours 1544

I am still worried about the annealing, perhaps I could save it, it I let the temp. go down on its own and then re-plug and get to annealing temp.?

I am going to bed now, setting the alarm clock to wake me in 2 hours time. And see again what is happening.

If anybody can come up with an advice meanwhile, what should I do - I shall be more than grateful

It is quite warm here now, but still this piece should be 2 hours in annealing zone........ this will not happen without controller.

Many thanks,
Havi

[Bert Weiss]

Havi

You have a relay that is stuck in the on position. Unplugging was the right thing to do. Your glass will cool at whatever rate the kiln allows. Tomorrow you can work on getting a replacement relay. They are probably available locally or not far away, if you know what you need. Look in the kiln manual to see if they give you a specification. It would be a good idea to buy an extra relay if you can.

After you get the relay replaced, you should slowly ramp up to 530ºC and then you have the choice to go back up to 815 or just anneal as you would have.

[Havi]

Thanks, Bert

Going back to bed.

Many many thanks,
Havi

[Havi]

On a second thought
This slab is being prepared for kilnforming over a thin fiber mold.
Why then refire it to anneal?
Can I simpley do the kilnforming - very carefully and then anneal properly?


Thanks, in advance Bert , or anybody else


Havi

[Brad Walker]

Havi,

Is the kiln working properly now? If the relay has failed, you can't refire the kiln until you replace the relay. Otherwise, it will most likely just continue firing as high as it can. (By the way, turning off the off switch on many kilns just turns off the controller box; if the relay has failed in the on position, it will continue to heat as long as it is plugged in.)

If the kiln is working properly now, I would be wary about refiring it until I know why it failed and then started working again. If I did fire the kiln again, I would watch it very carefully the next few firings.

Regarding the piece you fired, if it cooled slowly overnight it has probably annealed well enough for you to just proceed with the next planned firing. But make sure the kiln is working properly first!

[Bert Weiss]

Regarding the piece you fired, if it cooled slowly overnight it has probably annealed well enough for you to just proceed with the next planned firing. But make sure the kiln is working properly first!

I agree with this, but I would be conservative with the heatup schedule. There is probably a bit more internal stress than in a properly annealed piece, but not so much that you can't fix it and move on. The only anneal state that effects the piece is the last one that took place, at any given time. Once you heat above the strain point, it is a whole new situation.

[Havi]

Thanks, Brad

I am waiting for the piece to get REALLY cold now. Probabley tonight.

I will not use the kiln untill a real professional dealt with it.
Meanwhile, called an electrician and asked him if he knew something about relays - but in fact, when he came here - he could not help - said that does not know these relays - and left [without charging me]

I later called a specialist who is one of the best kiln technicians in Israel. Only he is too busy. He remembered me from years ago, and said he would come throught the week.

So I am hoping for the best.
I really need to trust my kiln now, I have a long , challenging project ahead of me - so it seems right to invest in waiting for things to be done the rioght way.

thanks, for the advices.

You know, I could not reach the point where I could unplug the kiln - because the hot kiln was on my way. 1:00 am , would not wake anybody up at that time. So eventually I realised I could stop the safety 'something' and this is what I did. The kiln seemd boiling

Hope for better news soon.

Thanks again,
Havi

[Havi]

Regarding the piece you fired, if it cooled slowly overnight it has probably annealed well enough for you to just proceed with the next planned firing. But make sure the kiln is working properly first!

I agree with this, but I would be conservative with the heatup schedule. There is probably a bit more internal stress than in a properly annealed piece, but not so much that you can't fix it and move on. The only anneal state that effects the piece is the last one that took place, at any given time. Once you heat above the strain point, it is a whole new situation.

thanks Bert.
I shall be very conservative on the next firing. Only first, I got to make sure that the kiln is really OK and trustworthy
That was a nightmare

Havi

[Bert Weiss]

Regarding the piece you fired, if it cooled slowly overnight it has probably annealed well enough for you to just proceed with the next planned firing. But make sure the kiln is working properly first!

I agree with this, but I would be conservative with the heatup schedule. There is probably a bit more internal stress than in a properly annealed piece, but not so much that you can't fix it and move on. The only anneal state that effects the piece is the last one that took place, at any given time. Once you heat above the strain point, it is a whole new situation.

thanks Bert.
I shall be very conservative on the next firing. Only first, I got to make sure that the kiln is really OK and trustworthy
That was a nightmare

Havi

The average mechanical relay is good for 100,000 clicks. Average means some last longer and others fail sooner. They can fail so that they won't close or so that they don't open. Not opening can be disastrous, and of course, this is the most common failure. The terminals fuse together.

[Havi]

Thanks, Bert
Even though what you say is Chinese to me.

I have been getting alarm messages for a while now - however those messages came on the opposite direction - when the temprature was going down. Usually I aborted the programme, made quickly a new one [suitable for the exact situation] and finished the firing.
This was the first time that the alarm came when the temp. was going up and beyond any control - just running quickly up , and I could not stop it with the on/off switch.

I am glad I have a whole elecrtic system for the studio, which is separate from the home electric system, and that I have this extra safety /security thing, which I shut down.

Havi
ps my friends here talk about 'quick silver' relays, do you recomend those?

[Bert Weiss]

Thanks, Bert
Even though what you say is Chinese to me.

I have been getting alarm messages for a while now - however those messages came on the opposite direction - when the temprature was going down. Usually I aborted the programme, made quickly a new one [suitable for the exact situation] and finished the firing.
This was the first time that the alarm came when the temp. was going up and beyond any control - just running quickly up , and I could not stop it with the on/off switch.

I am glad I have a whole elecrtic system for the studio, which is separate from the home electric system, and that I have this extra safety /security thing, which I shut down.

Havi
ps my friends here talk about 'quick silver' relays, do you recomend those?

Havi, if you thought the last post was hard to understand, this one is worse. I think what you are calling quicksilver is mercury. Mercury relays do last longer than mechanical relays. In industry in the USA, where OSHA (occupational safety and health administration) is monitoring, nobody uses mercury relays. The reason is, if one should break, OSHA will require that you remove your floor (even if the floor is concrete) Nobody wants to risk this. That said, I have never heard of one breaking open. Mercury relays are larger than mechanical relays, so I don't know if your box has room for this. I use solid state relays. These are good for many millions of on/off cycles. The problem is that they are heat sensitive, so they will not work mounted on the side of a hot kiln. When I use a solid state relay it is mounted on a board or in a box that is set on the wall 18" away from the kiln. For this reason, most kiln designers in the consumer market don't use them. The mechanical relays will work in a hot place. However they don't have a particularly long life. Every week on this BB, somebody reports their experience with this very problem.

The relay controls the heat in your kiln by turning the power on and off. The controller sends a signal to the relay to turn it on or off. The relay itself is simply a switch. Mechanical relays have contactors that close to turn on, and open to turn off. When these contactors fuse together they can not turn off and the heat will rise as fast as the elements can make it go up.

There are a few ways that you can protect your kiln from a stuck closed relay. They all cost money. The best is a high temperature limit controller. This requires a controller, a thermocouple, and a relay. The controller is set to a high temperature. If the thermocouple reports this temperature, the relay is opened and all power is shut down. Many controllers have the capability of adding extra thermocouples. You can set them up, with an extra relay to shut down the power if the temperature gets too hot. You can also simply add an extra relay to your circuit. The theory being that only one will fail at a time. The problem here is that there is no way, other than to look, to know if this has happened.

[Havi]

Thanks, Bert,
I hope that tomorrow, finally the kiln technician will come, and I shall discuss with him all these possibilities. I think that he is the best trained in Israel, and most knowledgable.

I want to do some pot melts and staff that needs 900 C degrees, and a bit more. So I do not know if I can install this extra thermocuple you mentioned, [or limit it to more temp. as high as 930C]

Also, I am afraid that the temp. I saw on the kiln controller, [840 C] was not the real temp. it seemed higher temp. At the moment I can't find the right word to define the look of the heat. the lower elements burning, looked really scary.

Havi

[Bert Weiss]

Havi

I'll guess that your guy knows his stuff. I'm sure he has made plenty of these repairs.

A high temp limit controller can be set to any temperature you like, and changed if you want also. So, you might keep it set to 870ºC, but if you want to fire to 930, you can set it at 950 or wherever you like. I'm not sure you need this, but it will prevent a disaster made by the kiln not shutting off while you are not watching it. This controller relies on a double pole relay, but it only turns on and off once in a while, so should work reliably. When I make a hitemp limit circuit, I put in a light switch that can turn off the power to the controller. This will automatically make the hitemp relay open up and it removes all power to the elements. If you want to do combing with a metal poker, this will make it much safer to do.

The regular relays used to control the elements are called single pole relays. These will turn the elements on and off, but if you should connect the element to ground there is a 120v potential that is the same as is in a regular house element (in the USA) I realize this is confusing, but your tech guy should understand it all.

[Havi]

Thanks, Bert

By now, finally the guy came, Changed ALL the 3 relays that were there [why should I call him again in 3 months?]
We discussed installing the safety thermocouple. He suggested at the beginnig something quite expensive. Then, I called a friend of mine who has understadning in electricty. This friend asked the electrician, not to cause me waste too much money.

So, when the electrician left he said he could install another thermocouple and connect it to a controller - in a cheaper way. I have an unused Bentrup controller [German, very good, but with very few segments] so we could do this combination, I believe.

I want very much to do the firing I planned to do. I know I should run a trial firing first.... I must decide what to do - and go on with this.
Thanks for the encouragement, it was the right thing at the right time!!!

Havi

[Bert Weiss]

Thanks, Bert

By now, finally the guy came, Changed ALL the 3 relays that were there [why should I call him again in 3 months?]
We discussed installing the safety thermocouple. He suggested at the beginnig something quite expensive. Then, I called a friend of mine who has understadning in electricty. This friend asked the electrician, not to cause me waste too much money.

So, when the electrician left he said he could install another thermocouple and connect it to a controller - in a cheaper way. I have an unused Bentrup controller [German, very good, but with very few segments] so we could do this combination, I believe.

I want very much to do the firing I planned to do. I know I should run a trial firing first.... I must decide what to do - and go on with this.
Thanks for the encouragement, it was the right thing at the right time!!!

Havi

Yes, replacing the relays now is cheaper than 2 more service calls. Yes a hitemp limit circuit can be expensive. If your friend can rig something using the Bentrup, I approve. I have to admit that I don't have a hitemp limit on my kilns, but I put one on every kiln I build for others. What this system does is give you assurance that an unmonitored kiln will not result in a disaster. I have nichrome elements which will self destruct before total disaster. Most kilns out there use Kanthal A-1 elements. These will take a much higher heat before destructing, so are far more dangerous.

[Havi]

I think I should copy all the info from here and save it, in addition to bookmarking it.

Another lesson I learnt from here!!!


So many thanks,

Havi