Old kiln stopped cycling - Failed infinity switch/relay

[Chalkie76]

After receiving some excellent help during the summer regarding my elements I’m back again with a new problem…..

It appears that now the kiln fails to cycle at some point and gets stuck on full power, it stops clicking and the temperature rises at a rate of 250 degrees per hour even when the dial is set to “2.5” which I think should be roughly 60%.  

Everything I read online says I need new relays but I’m wondering if my kiln even uses relays or if it’s an infinite switch or possibly something else?  
 
The kiln is a Cromarty CTL-17 and it’s over 40 years old but is structurally sound with new elements so I’d really like to bring it back to use.  
 

how can I tell if my kiln uses relays or an infinite switch?  The only thing connecting the elements to the “power dial” is in the picture attached, anyone any idea what it is? 
 

Thanks in advance 

 

[neilestrick]

Is that red box the backside of the dial?

[Chalkie76]

Yes it is and the only other connections in the kiln from there is to the elements and lid safety switch and obviously the power coming in. 
 

thanks for replying 

[PeterH]

The red box seems to have 20ER2 on it

This infinite switch advert says Will also replace a 20ER1 and 20ER2.
https://tdspares.co.uk/product/original-diamond-h-energy-regulator-simmerstat-burco-swan-water-boiler-thermostat-cooker

Edited November 21, 2023 by PeterH

[Chalkie76]

Aha!  An energy regulator- seems obvious now, so basically the control knob regulates the current being supplied to the elements by switching the power on and off for longer/shorter intervals much like a relay?  

[PeterH]

How an Infinite Switch Works
https://techcircuit.org/how-an-infinite-switch-works/

Surprisingly minimal inside the box.
how stove infinite switch works. Internals/inside of it

 

[Chalkie76]

Thanks Peter all makes sense and it’s done well to last as long as it has considering it’s just a piece of metal bending!  I think maybe me increasing the spec of my elements has bitten me here as previously the regulator would have been turned to max much earlier in the firing but now I have to hold at 60% for several hours to keep the temperature from sky rocketing - that’s a lot more clicks than its used to! 
 

I had previously considered buying a “plug and play” pid controller but got put off by not understanding how it all works, now I’m thinking my regulator on full and allowing a plug and play box SSR to regulate might be a good option now. 
 

or a new kiln……

[Bill Kielb]

38 minutes ago, Chalkie76 said:

now I have to hold at 60% for several hours to keep the temperature from sky rocketing

These switches traditionally last a long time,  but making sure they are not overloaded is important to their  longevity. Hopefully you are not at maximum amperage. If so, one solution - this can drive a more robust relay which then power your elements.

[Chalkie76]

Iooking at the replacements they are rated at 13amp and I’m drawing <10amps on 2.2kw elements so should be plenty of play.    What was the solution you were thinking of that would drive a more robust relay? 
 

I actually love how simple this kiln is and replacement parts seem to be quite cheap and readily available (if you know where to look)! Hopefully once I replace the regulator and count the cycle clicks on each setting I’ll be able to come up with a firing schedule that doesn’t nuke my mugs anymore!!

I’m Still tempted by the PID controller - in your opinion are they as straightforwards as they are marketed?). 
 

thanks again 
 

 

[Bill Kielb]

3 hours ago, Chalkie76 said:

I’m Still tempted by the PID controller - in your opinion are they as straightforwards as they are marketed?). 

PID programming (proportional, integral, differential) can be extremely challenging. Now days most are auto tune so that can help. Segment programming is a bit of a haseł as well for each firing but doable for many. SSR’s not exactly the miracle devices either but generally reliable. There are nuances though, for instance generally a definite purpose contactor needs to be installed ahead of the SSR’s to ensure potential leakage does not cause electric shock while loading the kiln. To that, there needs to be some safety circuit that drives that contactor such as a lid switch …….

If you are electrically savvy, then maybe a nice project with a temperature controller. For simplicity I usually suggest getting a bare - bones Bartlett controller and building upon it. It allows one touch cone fire programming so the simplicity is great and all that underlying setup and tuning is virtually done for you already.

I would suggest download any temperature controller install and configuration guide and see if it appeals to you or it reads like another language.

Edited November 22, 2023 by Bill Kielb