Jump to content
Sign in to follow this  
Sputty

Is This Normal? Kiln Suddenly Firing V-E-R-Y Sloo-O-O-Wly.

Recommended Posts

 I've always assumed that elements gradually lose their mojo, slowly building up resistance. But this increase in firing time seems rather sudden to me - over the space of only 3 firings.

 

Only guessing here, (I've not yet worn out any elements) but as you have less element material than in a larger kiln wouldn't the effect of deteriorating elements tend to show up much quicker?

Share this post


Link to post
Share on other sites

In my experience, the drawing out of the firing time is more gradual as the elements age gracefully. The sudden decline is worrisome, but I don't what else to test other than ohms of resistance. The conventional wisdom of resistance testing is that a measured resistance of more than 10% over specification indicates worn elements. However, you don't have a factory specification (yet) so no reference point to determine failure. When the new elements are installed, take a resistance measurement and write that down in your kiln manual so you have it for future reference.

Share this post


Link to post
Share on other sites
Guest

I'm not the resident expert on this but is it possible that the elements need to be replaced?

Share this post


Link to post
Share on other sites

How many elements are in this kiln? When my elements are getting old, the firing time gets longer slowly. When one of my elements has failed (element breaks and melts into a little puddle at the break) the firing time gets dramatically longer all of a sudden. If there is more than one element, losing one will cause this behavior.

Share this post


Link to post
Share on other sites

 

How many elements are in this kiln? When my elements are getting old, the firing time gets longer slowly. When one of my elements has failed (element breaks and melts into a little puddle at the break) the firing time gets dramatically longer all of a sudden. If there is more than one element, losing one will cause this behavior.

 

 

There are 3 elements, although each one sort of doubles back on itself, so a quick glance into the kiln looks like there are 6.

They are wired in series, so if one fails completely, there's no circuit at all.

However, during the last (half a) firing, I tested the voltages across each segment, and they were even across the 3 elements. If one element had gone 'a bit' bad (but not catastrophically), there would be a clue in an uneven voltage drop across one segment. No such luck.

It's the suddenness of the lengthening of firing time that puzzles me. To go from 8 hours to 12 hours in the course of 3 firings seems odd.

I had been hoping that it was a line voltage problem - I live rurally in France, where we are prone to... erm... variation. But it's fine - I checked all the way through the last firing.

I even racked my brains to try to remember if I'd included anything unusual in the kiln, which might have fumed and done mysterious instantaneous damage to the elements, but I really haven't.

When the new ones arrive, I'll check the resistance of one, and put that against the resistance of one coming out of the kiln. That should tell something, at least.

Gotcha. Yup you're right that's a different configuration from my elements. I have six elements, they are wired together in pairs, so three different circuits. Curious to hear the resistance comparison between new elements. Let us know!

Share this post


Link to post
Share on other sites

 

How many elements are in this kiln? When my elements are getting old, the firing time gets longer slowly. When one of my elements has failed (element breaks and melts into a little puddle at the break) the firing time gets dramatically longer all of a sudden. If there is more than one element, losing one will cause this behavior.

 

 

However, during the last (half a) firing, I tested the voltages across each segment, and they were even across the 3 elements. If one element had gone 'a bit' bad (but not catastrophically), there would be a clue in an uneven voltage drop across one segment. No such luck.

 

A change in element resistance won't affect the voltage. It'll still measure the same voltage regardless of the resistance change. The difference will be in how hot the element gets. You need to measure the element resistance.

 

If the relay stays on for most of the firing, that tells me that this kiln may under-powered for the temp you're firing to, and so a little change in element resistance will have a big effect on its ability to get to temperature.

 

Have you changed the thermocouple?

Share this post


Link to post
Share on other sites

No need to take elements out to measure resistance. I did hear you can take off the neutral connection if you are getting strange readings but I just put the probes where they entered/exited the kiln to measure when they are installed.

 

Have you opened the controller to see if any components are looking suspect?

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  

×

Important Information

By using this site, you agree to our Terms of Use.