Trouble shooting Cress kilns

[STONEWARECAFE]

Wondered if anyone has had trouble with cress kilns not powering the coils and what the most likely cause would be. I bought a Cress FTX 23 UP and I have trouble believing both relays are dead since I can't get any coils to heat up. (Can't even find the "UP" designation in the schematics they heve) How likely is it going to be the firemate A-D switch? Or is it possible the thumbwheel advancement which increases power  has failed? have never found a schematic on either one of these to see how they function which is why I don't mess around with these kilns too often but here I am. Any thoughts?  Thanks Stonewarecafe. Sorry don't remember how to downsize jpeg files

[neilestrick]

Wiring diagrams can be found HERE. If yours isn't on there then call Cress and they can get you one. I don't know what the UP designation means, but it's very possible that the wiring is the same as the other FTX23 models.

You're probably going to have to track the flow of power with a meter and figure out where it stops. I've seen two relays die at the same time, but I've also seen all the other parts die, too.

[STONEWARECAFE]

No worries, already planned on metering all connections. And have already gone through Cress diagrams, turns out it was a badly stamped plate .It is actually a Cress FTX 28 UP and they sent me a couple of diagrams on it.   Hoped someone had run into special circumstances especially with the thumb-wheel drive. It's one of the reasons I don't use Cress kilns because there is no diagram or exploded view of how this system energizes the relays and coils and there has never been an explanation that really tells anything about how this system interacts with all the various parts. but maybe I will see about opening the thumbwheel to see how it works and post pictures of the internal parts and possibly explain how this mechanism works.

[PeterH]

8 hours ago, STONEWARECAFE said:

but maybe I will see about opening the thumbwheel to see how it works and post pictures of the internal parts and possibly explain how this mechanism works.

The "magic" lies in the infinite switch below the thumbwheel
from INSTRUCTIONS FOR CHANGING THUMBWHEEL SWITCH OR MOTOR https://tinyurl.com/yc2bxy22

The shaft on the switch is turned
- by the thumbwheel for manual control
- by the motor for automatic control

When the shaft is turned to full on the mains passes through the switch unimpeded ...

At lower settings the mains passes through in bursts ...

Effectively allowing a continuous range of duty-cycles (the fraction of time the mains gets through).

Normally the duty cycle steadily increases as the firing proceeds.

For most purposes this "black box" description is all you need. If you want an explanation of how the switch does this then the best description I've seen is in How an Infinite Switch Works https://tinyurl.com/4ut2zk8z

PS Infinite switches are pretty minimal internally https://youtu.be/hyGna58BB3k?t=74

[STONEWARECAFE]

Wow! Thanks so much for this schematic! Just knowing an infinite switch is on the bottom clears up many questions I had since I have never pulled one these off a cress. I thought the upper A<B<C<D control was the only infinite switch. Thanks again.

[neilestrick]

It's the world's most complicated infinite switch.  These types of mechanically automatic kilns are a stepping stone between turning switches by hand and digital controllers. They work great and do exactly what they were designed to do, but they can be difficult to troubleshoot because there are a lot more parts than a typical kiln.

[STONEWARECAFE]

Funny you mention it that way. Way back in the day we had a mechanical clock connected with a gear to our Partlow gas controller to turn down the amount of gas in the annealer slowly in order to anneal our glass. Cress made a fancier solution for electric kilns.