Cress kiln Wont Start

[JTMD]

Ive got an older Cress Kiln - EF-23    has the infinite switch and timer along with the sitter.  

When I press start the relay engages but when I release the start button it disengages and nothing further happens.  If I hold the button it appears to run normally (elements heat and such)

any idea what is failing?

[neilestrick]

Make sure the Kiln Sitter timer is not at zero.

[JTMD]

5 hours ago, neilestrick said:

Make sure the Kiln Sitter timer is not at zero.

thanks!   the timer has the button I pushed.   i've tried it at a variety of time settings  with no change.  maybe the timer is bad?  is there anything else it could be?

[neilestrick]

Sometimes the Sitter mechanism gets gummed up or corroded. Unplug the kiln, access the back side of the Sitter, and look for the flat parts that are mounted to the back side of the Sitter plate. There's a wire spring an another part that moves when the button goes in and out. Spray a little WD-40 on those parts and push the button in and out a bunch of times and see if it'll catch.

[JTMD]

29 minutes ago, neilestrick said:

Sometimes the Sitter mechanism gets gummed up or corroded. Unplug the kiln, access the back side of the Sitter, and look for the flat parts that are mounted to the back side of the Sitter plate. There's a wire spring an another part that moves when the button goes in and out. Spray a little WD-40 on those parts and push the button in and out a bunch of times and see if it'll catch.

ok, it sounds like *maybe* you might be thinking of another Cress model.   My sitter just has a switch, that appears to be working OK and uses a seperate timer/switch. Here's a link to a video that shows my problem: https://youtu.be/uv5Iz08LWzk
 

[neilestrick]

I'm not familiar with that system. Cress has a few oddballs out there. I can't find a wiring diagram for it, either. This is different than the issue with the Sitter in the other thread you're following, as that kiln does not have that timer. Does turning the timer knob have any affect on it? All I can say is that you could wire directly from the Sitter to the infinite switch and not use the timer, but without a wiring diagram I can't be certain about that. Are there any relays or anything else in the box?

[JTMD]

20 minutes ago, neilestrick said:

 Are there any relays or anything else in the box?

Just the main relay.   I have a wiring diagram Cress sent me:

 

EF23.pdf

[neilestrick]

Ahh, so it has the thumb wheel and all that. Cress is going to be the best help here. If you ned to replace things in there and they're pricey (which they can be), you could wire each element to its own infinite switch and forget the thumb wheel, relay, and timer. You would just have to manually turn it up then.

[JTMD]

Actually when I originally purchased it, I intended to gut the controls and put in my own (I design automated machines for a living).  I was going to use it to heat-treat aluminum castings.  I ended up getting a much larger oven designed for heat treating and never touched this kiln - which I got from an ebay ad 15 years ago.
I live in Joshua Tree, California - an art-centric community and a young promising ceramics artist is having problems getting kiln time for her work.  I pulled this kiln out intended to give it to her but discovered this problem.   I've sourced all components (except for the motor that drives the thumbwheel) and have no problem replacing parts, I just need to know which one  
Im not an artist and don't know how to use a kiln (although I've learned a bit from this ordeal).  I'd put new controls on it but that would end up costing more than a new/decent used one- and it's operation would be foreign to those who are kiln-familiar .  I'd hate to just abandon this one.

 

[neilestrick]

Talk to Cress, it may just need an simple inexpensive part. Trimming it down to two infinite switches would be cheap, though, about $30 per switch.

[Bill Kielb]

3 hours ago, JTMD said:

My sitter just has a switch, that appears to be working OK and uses a seperate timer/switch

I see the timer push button switch in your video, likely the timer says turn past …… to actuate so you may want to turn it up to some minimum period and see if the push button will stay engaged. The interaction between the timer and sitter are traditionally mechanical to ensure positive shutoff and appears to be the case here looking at your kiln diagram. Your sitter is able to stay engaged on its own though so maybe an update to the drawing is in order and your comment that the relay engages when you press the start switch indicates the drawing might need an update. Pictures of the inside of this thing would reveal more.

42 minutes ago, JTMD said:

(I design automated machines for a living)

I am with Neil though, two infinite switches and a functional sitter ( with a functional safety timer) make this kiln easier to operate and learn how to fire with. I designed DDC systems for buildings for years, the good thing, this should be in your wheelhouse. Infinite switches have been used for resistive loads for years and are economical and dependable. IMO restoring the old firing control scheme is likely not worth it.

Edited November 1, 2023 by Bill Kielb

[JTMD]

14 hours ago, neilestrick said:

Talk to Cress, it may just need an simple inexpensive part. Trimming it down to two infinite switches would be cheap, though, about $30 per switch.

I'll give them a call today, hopefully they wont dismiss it as being too old.  It's really in remarkable condition internally, probably was never used much.
I'm not excited about making changes using this tech, if I'm going to change it I'll gut everything except the sitter and use modern interfaces and software - either Labview or C.  I like Labview for this sort of thing since it comes with a built-in GUI but on the other hand, required a windows platform.  a USB DIO and some solid-state relays and it should be good to go.

 

besides, I dont have a clue how the "infinite Switch" works, putting two in there would boggle me 

[PeterH]

42 minutes ago, JTMD said:

besides, I dont have a clue how the "infinite Switch" works, putting two in there would boggle me 

It produces a pulse-width modulated power supply.
https://techcircuit.org/how-an-infinite-switch-works/

Edited November 1, 2023 by PeterH

[neilestrick]

58 minutes ago, JTMD said:

besides, I dont have a clue how the "infinite Switch" works, putting two in there would boggle me 

HERE. They're actually made for electric ovens and whatnot. A dial that goes from 1 to 6, usually. Easy to install, easy to wire up- two hots in from the Sitter, two hots out to the elements. The switch cycles power on and off to control how quickly the elements heat up. They can only handle 15 amps, so they are generally used on smaller kilns where a pair of elements draw less than 15 amps. On larger kilns with element pairs that draw more than 15 amps you can use a 4 position switch like Skutt kilns use, which can handle 20 amps. 

I would not try to put any electronics directly into the kiln control box. It does not have adequate heat protection for that. You'd want to wire the Sitter directly to the elements and plug the kiln into an external box that houses all the electronics and relay(s). A controller built for kilns like the Bartlett Genesis is the simplest way to go. Easy to install and set up, and it has cone firing modes so it's easy to use for clay work.

[JTMD]

48 minutes ago, PeterH said:

It produces a pulse-width modulated power supply.
https://techcircuit.org/how-an-infinite-switch-works/
 

OK, I know what a infinite switch does, it's how it's used in this kiln that's confusing.   It has a motor attached to the switch that appears to be controlled with yet another switch.  My assumption is that the infinite switch is "throttling" the current so the elements are not at full heat - then the motor moves the infinite switch over time to raise the current to increase the heat of the elements (and thus the kiln)
Adding a second switch?   <mind blown>

[JTMD]

25 minutes ago, neilestrick said:

I would not try to put any electronics directly into the kiln control box.

oh no, I wouldnt do that.. exactly.   The DIO interface is hardened so it's a great industrial part.  I'd put it in an enclosure attached to the existing electrical box to avoid heat conduction.   the solid-state relays would be ok in the existing box.  and I'd keep the sitter as-is.
Heck, with using Labview I could use the same kiln for ceramics and heat-treating, possibly put a crucible in it to melt aluminum..  it would just take a different profile in the program.. easy

But for now, I'm going to pull and test the timer.  I gotta hunch it's internally stuck on zero 

I've got another kiln, larger and propane fueled.  maybe I'll offer her that one.  It's been idle for at least 16 years - my sister-in-law bought it new and only used it a few times before she passed.  I have some really amazing stuff that she did with it.

[PeterH]

Certainly ingenious, and devised years before digital controllers were a possibility.

 

[neilestrick]

4 minutes ago, JTMD said:

the solid-state relays would be ok in the existing box.

Not without an insulated baffle and/or a cooling fan.

[JTMD]

Well it just got decided...  I'm gutting the system.

I've been unable to find a replacement for the original timer.  Cress published a replacement start/timer some time ago (an ITC product) and I've only been able to source that one from the manufacturer - $260 +tax and shipping and 2 week lead time.

[Bill Kielb]

1 hour ago, JTMD said:

OK, I know what an infinite switch does, it's how it's used in this kiln that's confusing. 

Just a thought or two,
This is one of the only kilns that operate in this way in an attempt to semi automate the process. 99% of manual kilns are fired by simply folks learning to turn them up periodically to achieve their desired firing rate for that kiln. It actually is beneficial to learn the particular kiln and the why and when part of turning it up to achieve a desired rate. A pyrometer can be added as well which should allow most any type of firing.  If you install infinite switches you simply install one per element set, no motors, timers, relays etc… the switch just cycles on and off on a duty cycle established by the setting on the knob. They work really well, have worked forever and lots of manual fired equipment out there still in service, meaning not a bad thing for a new potter to learn.

Labview to me is overkill, most any any pid heating control will work and are thermocouple capable. SSR’s are great but ought to contain a mechanical safety to preserve safety in operation. As a gift do you want this to be a unique kiln to program or something conventional? SSR’s require decent cooling and thermal design, especially for passive cooling, not many folks I have found do this well up front.

Electrical safety is a thing, kilns are super simple devices but nuanced in the electrical safety aspect. My thought is making it unique and one off in programming without a solid knowledge in electrical safety and safe operation of a kiln has risks associated with it. I am still predisposed to a fully functional sitter and two infinite switches. If the sitter timer is mechanically interlocked to the sitter then a conventional timer without a start switch is  probably available, economical and very popular. We never found out what that switch controls - might be worth opening the box and checking. Even if automated you will need something to ensure shutdown so repairing this one is likely necessary. ………. Just thinking …….

Edited November 1, 2023 by Bill Kielb