Jump to content
Sign in to follow this  
kennyd67

Electric Kiln Controller Issue

Recommended Posts

I have an electric kiln with a hobbyceram HC8 controller. We have programmed the HC8 for a slow profile to cone 04 but the kiln fired at full. It rose to 1060 degrees C in only 5 hours, or about 176 degrees C per hour. I had programmed the system for only 70 degrees C per hour. does anyone know what caused this and what we can do to fix this from occurring in the future? I am not sure if anything survived this firing, hoping for the best but this was a very fast firing. 

Share this post


Link to post
Share on other sites

not that you WONT get a response here, but given that it is a european kiln, you might have better luck contacting the manufacturer directly...  Additionally, if you want any chance of having your question answered, you might want to elaborate on what a "slow profile" is--is that a custom program of ramps and holds that you input yourself, or is it a preset that comes loaded on the controller from the factory?  

Share this post


Link to post
Share on other sites

the slow profile would be a custom set of ramps, was looking for a maximum ramp of only 70 degrees C or about 158 degrees F per hour. Instead of this the kiln fired at a rate of about 350 degrees F per hour. Waiting for it to cool down to see if anything survived.

Share this post


Link to post
Share on other sites

Most kiln controllers have the option of reviewing what program you actually programmed, as sometimes opposed to the program you thought you put in.  On our kiln controller it is labelled as "Preview".  I always push this button 30 seconds or so after I push "Start".  Every once in a while I see I've made a mistake - it seems inconceivable, but there it is - a raucous fact.

 

You can usually bring this information up after the firing is complete.  Perhaps there is some other problem, but dealing with computers this is not likely.  Computers normally stupidly do exactly what you told them to do.

Share this post


Link to post
Share on other sites

Yeah, I hate to say it but it was probably user error. As Norm said, if there's a review button, always hit it after you start the kiln to make sure you did what you think you did. After 20+ years of firing kilns, I still us the Review button every time I fire. You can also use it after you fire to see what you did.

 

It's also possible there was a controller or thermocouple issue, but that is rare. However make sure your controller is set for the type of thermocouple you are using.

clay lover likes this

Share this post


Link to post
Share on other sites

we did review the program and everything appeared correct. The manufacturers website is not very helpful, I may have to call them directly to see what went wrong. This is actually the second time it happened to us, the first was with some glass bottles we were slumping so it did not really cause any issues. Crossing my fingers that my pots and bowls are still intact. The kiln and the computer are a matched set so I have to believe that the computer is designed for the type of thermocouple in the kiln. Right now I have to put any further ceramic firings on hold until I figure this out. I still have several pieces ready to go, guess they sit on the shelf for awhile. 
 

Share this post


Link to post
Share on other sites

we did review the program and everything appeared correct. The manufacturers website is not very helpful, I may have to call them directly to see what went wrong. This is actually the second time it happened to us, the first was with some glass bottles we were slumping so it did not really cause any issues. Crossing my fingers that my pots and bowls are still intact. The kiln and the computer are a matched set so I have to believe that the computer is designed for the type of thermocouple in the kiln. Right now I have to put any further ceramic firings on hold until I figure this out. I still have several pieces ready to go, guess they sit on the shelf for awhile. 

 

 

Second time? Now that changes things! It may well be a computer issue, or you did the same thing twice. Most of these controllers can use different types of thermocouples- type K or type S, for example. So that is definitely still a possibility.

Share this post


Link to post
Share on other sites

We did not use witness cones, probably would have been a good idea. We do know that the kiln reached temp yesterday because the glass bottles slumped just like normal. Also the computer beeped when it achieved my target temp, however it appeared to completely ignore the programmed profile to get there and also continued to rise in temp until I shut it off. It really just looks like it ran at full power all the way up. I do not know what the pieces look like yet, the kiln is still cooling and I wont be able to open it until the morning. 

Share this post


Link to post
Share on other sites

Well, everything survived! :) now just hoping I will not have any issues with the glaze pitting, bubbling or cratering. The pieces are definitely bisque now, just not sure if enough gas escaped during that fast of a firing. Only 5 and half hours, if that worked and I don't have problems with the glaze then maybe that HC8 is smarter then I thought.

Share this post


Link to post
Share on other sites

I have seen a few kilns ramp up too quickly with a relay problem.  The relay may be sticking in the on (closed position).  This causes the element to heat continuously in spite of what the controller is attempting to do.  You can usually test if the relay is fused closed but if it sticks intermittently it will be difficult to test the relay. 

Share this post


Link to post
Share on other sites

There's the info we needed! If it continues to rise after reaching target temp, then you likely have a sticky relay as smallshop said, or there's something really wrong with the controller. If it's stuck badly, it will come on as soon as there's power to the kiln. If it's intermittent, then you have to start up the kiln on a ramp at full speed, wait for the relays to switch on, check them with a meter to see if they all come on, then hit stop and test with a meter to see if the relays all shut down. You may have to repeat this 10 times or more to get a sticky one to stick. And even then it may not do it because sometimes they only stick when they get hot, like at the latter part of a firing. be careful, as you'll be working around live electricity to do the testing. A sticky relay should be replaced. If all the relays are older, then replace them all.

 

Your controller probably should have give you an error code for going too fast, but maybe it was still within its acceptable speed range for that profile.

Share this post


Link to post
Share on other sites

Neilestrick did a good job of explaining it.  To answer your specific question of how to test a relay you will need a multimeter and some understanding of the relay diagram.  Basically you're making sure the open contacts are open when the relay coil isn't powered.  A relay stuck closed (permanently) will have closed contacts that should be open.  As Neilestrick mentioned though, an intermittent problem is very hard to test. 

 

I do know on the few kilns I work around, when In doubt on relays we just replace them all at once.  This is for a business that earns money for each firing though so it may differ for a hobby kiln.

Share this post


Link to post
Share on other sites

Well, we did another firing and have the following observations. First we verified the the programming before and after starting the kiln, everything was programmed correct. Next I had programmed in a 10min soak at 121 c and the kiln reacted properly when reaching this temperature. During the 10 minutes we could hear the kiln start and stop several times as it reacted to keep the temperature near the soak level. From there the kiln ramped up at a very consistent but fast rate to my target temperature of 1060 c and beeped to let us know it was ready. Noticeably it did not shut off yet, because it ramped up as quick as it did I decided again to let it run to 1076 c to make sure the work was done. Reading information from the manufactures catalog makes it seem like this kiln and computer are just designed to speed up the process and so far it seems to know what it is doing. If I do not have any problems with my glazes and I can can get consistent results with a 5 and 1/2 hour firing then my electric bill says thank you. Pictures may be uploaded of some of the pieces after my glaze firing.

Share this post


Link to post
Share on other sites

Most computer controlled kilns have a number of firing speeds to choose from, in addition to preset cone-fire programs.

 

I have decided to use a custom program to bisque very thick pieces of clay, and I'll post the results.  Most computer controlled kilns let you program your own firings in addition to using the pre-programmed cone-fires.

 

http://community.ceramicartsdaily.org/topic/5527-firing-very-thick-pieces/

 

It is very energy efficient to fire quickly if your ware is happy with it.  In smaller kilns the thermal lag will be less of a problem so much of the firing can go very quickly, and they usually have a high amount of wattage per cubic foot so the can fire as quick as you like.

 

Well, we did another firing and have the following observations. First we verified the the programming before and after starting the kiln, everything was programmed correct. Next I had programmed in a 10min soak at 121 c and the kiln reacted properly when reaching this temperature. During the 10 minutes we could hear the kiln start and stop several times as it reacted to keep the temperature near the soak level. From there the kiln ramped up at a very consistent but fast rate to my target temperature of 1060 c and beeped to let us know it was ready. Noticeably it did not shut off yet, because it ramped up as quick as it did I decided again to let it run to 1076 c to make sure the work was done. Reading information from the manufactures catalog makes it seem like this kiln and computer are just designed to speed up the process and so far it seems to know what it is doing. If I do not have any problems with my glazes and I can can get consistent results with a 5 and 1/2 hour firing then my electric bill says thank you. Pictures may be uploaded of some of the pieces after my glaze firing.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×