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the hard way!

Lesson #1: When two of the relays in your kiln fail, replace them all. Why: I recently replaced two of the four relays in my Paragon GL24AD kiln. A couple of firings later, yup, another one failed. Two more are now on order.

Lesson #2: When you're having relay problems, DON'T USE THE KILN! I carefully watched a slump firing of 8 pieces until the slump was done, skipped to the next ramp, left the studio. Big mistake. I didn't realize it at the time, but the relay that controls 2/3 of my top elements was stuck in the ON position. Everything very well done. Fortunately nothing spilled out of the molds, which are cooling AFAP now, with the kiln unplugged.

The strange thing is that at first this relay was not allowing any power to these elements, so I only had 1/3 of the roof elements firing, but failed in the closed position this last time. I'm out of business until the new relays arrive in a few days. Guess I'll be burning (!) the midnight oil for the next few weeks, getting ready for the big Oregon Glass show (Glass Gallery) coming up April 23-25. Ya'll come, ya hear?

Paul

Paul Bush wrote:the hard way!

Lesson #1: When two of the relays in your kiln fail, replace them all. Why: I recently replaced two of the four relays in my Paragon GL24AD kiln. A couple of firings later, yup, another one failed. Two more are now on order.

Lesson #2: When you're having relay problems, DON'T USE THE KILN! I carefully watched a slump firing of 8 pieces until the slump was done, skipped to the next ramp, left the studio. Big mistake. I didn't realize it at the time, but the relay that controls 2/3 of my top elements was stuck in the ON position. Everything very well done. Fortunately nothing spilled out of the molds, which are cooling AFAP now, with the kiln unplugged.

The strange thing is that at first this relay was not allowing any power to these elements, so I only had 1/3 of the roof elements firing, but failed in the closed position this last time. I'm out of business until the new relays arrive in a few days. Guess I'll be burning (!) the midnight oil for the next few weeks, getting ready for the big Oregon Glass show (Glass Gallery) coming up April 23-25. Ya'll come, ya hear?

Paul

Have ur relays on a slowest cycle possible

It is posible with these new computor controlers 2 have relays cycle in seconds which is not good 4 some types

My view is if they fail U got some problem either duff units or elsewhere

Brian

Having had a kiln control fail and do major damage to a brand new kiln...over-heated and burned out a couple elements, large amount of glass ran off the shelf and ate deeply into the kilnwashed bottom of the kiln and up the bottom layer of side fire brick....I installed a kiln sitter and use it as a back up shut off. I use a cone in it that is high enough that it won't shut the kiln off during a normal firing so that it doesn't keep me from annealing, but would shut it off if things went out of control again. It probably wouldn't save the glass but it would save the kiln. Lesson learned.

Judith

Judith Andre wrote:Having had a kiln control fail and do major damage to a brand new kiln...over-heated and burned out a couple elements, large amount of glass ran off the shelf and ate deeply into the kilnwashed bottom of the kiln and up the bottom layer of side fire brick....I installed a kiln sitter and use it as a back up shut off. I use a cone in it that is high enough that it won't shut the kiln off during a normal firing so that it doesn't keep me from annealing, but would shut it off if things went out of control again. It probably wouldn't save the glass but it would save the kiln. Lesson learned.

Judith

A good idea Judith, but I don't think it's possible to install a kiln sitter in my kiln, which is a Paragon GL24AD, a front-loading steel-encased box. Am I wrong? I'd love to have a back up system. The good news about this is that my kiln overfired during a slump fire, and the molds kept the glass from flowing off the shelf. Got some amazing bubbles, but no brick damage.

Paul

Paul Bush wrote:

Judith Andre wrote:Having had a kiln control fail and do major damage to a brand new kiln...over-heated and burned out a couple elements, large amount of glass ran off the shelf and ate deeply into the kilnwashed bottom of the kiln and up the bottom layer of side fire brick....I installed a kiln sitter and use it as a back up shut off. I use a cone in it that is high enough that it won't shut the kiln off during a normal firing so that it doesn't keep me from annealing, but would shut it off if things went out of control again. It probably wouldn't save the glass but it would save the kiln. Lesson learned.

Judith

A good idea Judith, but I don't think it's possible to install a kiln sitter in my kiln, which is a Paragon GL24AD, a front-loading steel-encased box. Am I wrong? I'd love to have a back up system. The good news about this is that my kiln overfired during a slump fire, and the molds kept the glass from flowing off the shelf. Got some amazing bubbles, but no brick damage.

Paul

I think you can Paul, but it's beyond my electrical expertise. You'll need to drill one hole through the side of your kiln so the trippng apparatus can enter the chamber, screw the box to your kiln, and run the electricals through the kiln sitter. So, doable, but I'm sure the manufacturers would look at your warranty askance if you did it. Brock

Well, my kiln's long out of warranty - naturally - so that's not an issue. But doing the necessary wiring definitely is. Any volunteers?

Paul

Kiln sitter seems like a reliable safety device.

My kiln has two set of relays serially. This is an European requirement.
One set is operated
by the controller, the other set is triggered by
- door switch, cutting off if the kiln is opened
-if the thermocouple detects a temperature 20 deg C over the highest set value.

The risk remaining is a thermocouple failure.
I know there is something called heat fuses. A bit of
low melt wire. If it melts, the circuit breaks.

Does anyone have experience of those?

-lauri

You can add kilnsetter to your kiln. Basically you want the timer part added, where if you go over your estimated time for a firing it will shut it off.

You will be basically be adding it on to one of your wires.

but do you really think it is necesary.. If one of your relays breaks in the closed position then that element or set of elements will stay on. You probally have 4 relays in your kiln. The other 3 will turn off so your kiln will go down and get no more than 1000 °. There is no concern that your kiln will do any damage to anything out side of the kiln if your kiln is away from the walls. The damage to the piece will happen either way.. get to hot or not anneal correctly. I assume that you do not fire your kiln if you are gone more than the work day or so.

But if you want to do it then drop me an e-mail and I will look up your wiring diagram and tell you exactly what wire to put this one, and I cna even help you get a kiln setter.

Stuart kilnrepair@yahoo.com

Stuart Clayman wrote:You can add kilnsetter to your kiln. Basically you want the timer part added, where if you go over your estimated time for a firing it will shut it off.

You will be basically be adding it on to one of your wires.

but do you really think it is necesary.. If one of your relays breaks in the closed position then that element or set of elements will stay on. You probally have 4 relays in your kiln. The other 3 will turn off so your kiln will go down and get no more than 1000 °. There is no concern that your kiln will do any damage to anything out side of the kiln if your kiln is away from the walls. The damage to the piece will happen either way.. get to hot or not anneal correctly. I assume that you do not fire your kiln if you are gone more than the work day or so.

But if you want to do it then drop me an e-mail and I will look up your wiring diagram and tell you exactly what wire to put this one, and I cna even help you get a kiln setter.

Stuart kilnrepair@yahoo.com

I was referring to a mechanical kiln sitter, a Duncan, using cones. Brock

Brock,
I would think that the concern would be time. But if the concern is that a slump firing or tack firing gets to hot then each time there is a different type of firing the cone would be changed. Also, the installation would be harder since besides hooking up the electrical part a hole would be added thru the brick to put in the cone holding part.. but this installation is also doable.

Stuart,

I would think the problem is top temperature. That is where the cones are made to work. Enough heat work, and they trip. No over firings. Brock

that is true.. but the top temp for a full fusing and top temp for a slump would be different, and the problem with this was that the slump went too hot.

Stuart Clayman wrote:that is true.. but the top temp for a full fusing and top temp for a slump would be different, and the problem with this was that the slump went too hot.

Yeah? Different cones! Same as setting different times, except for a slight expense in cones. And a fail safe that time does not necessarily deliver, precisely because it is an estimate. Brock

Ok, I need to explain something.. Brock understand but I got a few e-mails from others about what I wrote.

What Brock was suggesting was to use the controller normally. In case there was a problem use a cone that would bend and trip the setter only if the temp got hotter and for a longer time. Hopefully if the correct cone was used and the kiln worked well, then the cone would not bend and stop the kiln. But if you got a run away and the kiln got hotter than what you set the controller to and the controller did not cut the system off (which it should), then the cone would melt and the kiln sitter would shut everything off. It would be used only as a backup failsafe system.

That was exactly what I was suggesting. The rest of this sad story of my runaway kiln (when I was sleeping, most of my firings take too long to be there all the time) was that there was some kind of weird incompatability between my new Euclid kiln and my old Kilntrol controller that I had been using with my Skutt kiln. I had bought the Kilntrol primarily because it had the capability to store a lot more programs than most. It was advertised consistantly in national glass magazines. How was I to know that Larry, the owner, designer of the equipment really didn't know what he was doing? I even checked with him before I ordered my new kiln to make sure things would be OK. After my melt down disaster I had some modification made to my kiln to supposedly prevent this from happening again. Paid Larry another 300.00 to fix the controller, even though I felt the whole mess was his fault. At this time, I also had the kiln sitter (setter?) put on. Within about 4 firings it failed again. This time I was there to see it and didn't ruin anything, not even my glass. Larry would not return my calls when I tried to contact him. I now have a very expensive paper weight in my kiln room sitting next to my Barlett controller. Have had no trouble with either the kiln or my new controller. A very expensive lesson learned.

Judith

I've kept out of this discussion for a while but here it my 4 cents.

Mechanical relays are a lousy choice of relay. Companies use them for a few reasons though. For one thing they are acceptable when mounted on the kiln as they are less heat sensitive than a solid state relay.

Mercury relays can be good unless you happen to break one open and then you have more trouble than you would want. Few companies will open themselves to that sort of liability.

My industry experts, who likely have more experience working with temperature control than anybody reading this board, heartily suggest using solid state relays. The inexpensive version is an SSR. The more expensive version is an SCR. Solid state relays are good for millions of contacts, whereas mechanical relays are not even close. The cost of an SSR and a mechanical relay are pretty close. I have been running SCR's since the early 80's and have had one runaway since then.

So why don't the kiln manufacturers use them on their kilns. Basically because SSR's fail if they get too hot. They create some heat themselves so mounting them in a hot place is not a good design. The solution is simply to mount your controller and relays on a board on the wall away from your kiln. You will need long thermocouple wire to do this as well. Since this does not make a neat, simple package the manufacturers have not gone this route.

Safety systems are required by code for industrial kiln installations. Not just any system will meet the specifications. You need a particular type of hitemp limiting controller. This unit has it's own thermocouple, and is wired in to a system so that it has to be on for the whole system to work. You choose the hi temp limit and if it's themrocouple reaches that temp, it trips the power to your elements, shutting them off. Duralite sells these units made by Watlow. There are a myriad of reasons why other systems, while they might work OK, don't do all the things that the acceptable units do. A cone sitter can easily fail and is not a code worthy solution.

This is a typical situation where the best solutions are more complicated than the companies making kilns for hobbyists and professionals are willing to set up.

This is one of many reasons I think building your own kiln can get you a much superior unit to a store bought kiln.

Stuart Clayman wrote:You can add kilnsetter to your kiln. Basically you want the timer part added, where if you go over your estimated time for a firing it will shut it off.

You will be basically be adding it on to one of your wires.

but do you really think it is necesary.. If one of your relays breaks in the closed position then that element or set of elements will stay on. You probally have 4 relays in your kiln. The other 3 will turn off so your kiln will go down and get no more than 1000 °. There is no concern that your kiln will do any damage to anything out side of the kiln if your kiln is away from the walls. The damage to the piece will happen either way.. get to hot or not anneal correctly. I assume that you do not fire your kiln if you are gone more than the work day or so.

But if you want to do it then drop me an e-mail and I will look up your wiring diagram and tell you exactly what wire to put this one, and I cna even help you get a kiln setter.

Stuart kilnrepair@yahoo.com

The interesting thing about what happened Stuart, is that the only elements that were firing were the ones controlled by the stuck-closed relay, which just happens to control approx. 2/3 of the roof elements. Plenty hot enough to boil glass - I have the pieces to prove it!. I don't know what the top tempurature was, but it was enough to cause the glass to get soft enough to close the vent holes in the molds, and form large, silver-dollar-sized bubbles that stick up about 3/4" to 1" high. It didn't get hot enough that the glass pooled in the low center of the molds (these were Bullseye's 8" and 4" square sushi molds). It pretty much stayed in it's original fused shape (2-layers of 3mm glass), except for some rounding over on one corner of each piece, and LOTS of needling.

Paul

Paul,
It is interesting.. Since I started repairing the kilns I was told that most of the times the relays break in the open position and they will not work. But I have replaced more of them with the relays that are stuck closed and keep firing even when the controller is not telling it to fire. Even with a run away the kiln will controll everything, so that the worse that can happen is that you will damage the piece. I have never had to replace any elements when a relay was damaged. I would think that the kiln sitter with the cones are a little over kill but it can keep the kiln from getting hotter than you expect. The timer might be a better solution since the elements will not always be the ones that generate the most heat. But either or both can be done. Or else you can do as everyone will tell you to do.. Be at the studio when the kiln is on... Someone e-mailed me recently and asked if what everyone was telling her was correct.. Everyone was telling her to stay home when the kiln is running. that is the correct answer. I told her to e-mail them back with the correct question.. ask if they stay near the kiln when it is running. We know that most of the time you will not get the same answer.

I agree with Bert about SSR's although I've heard differing opinions. Some people swear by mechanical relays while others prefer SSR's. With the help of TOB (the other Brad), I installed a shunt trip circuit breaker on my controller. I can program it to shut the kiln down if it goes over the high temperature of any particular firing. I also have a fan installed inside the controller box which vents heat out of the box through holes in the top. The controller is mounted on the wall not on the kiln. Before these modifications, I had two melt downs due to the failure of my SSR because of heat build up in the controller box. Knock on wood...I've had no further problems! I often wonder why kiln manufacturers continue to mount controllers on the sides of kilns where they are exposed to high heat instead of a wall mounted unit, similar to the Skutt Clamshell controller.

Avery

Avery Anderson wrote:I agree with Bert about SSR's although I've heard differing opinions. Some people swear by mechanical relays while others prefer SSR's. With the help of TOB (the other Brad), I installed a shunt trip circuit breaker on my controller. I can program it to shut the kiln down if it goes over the high temperature of any particular firing. I also have a fan installed inside the controller box which vents heat out of the box through holes in the top. The controller is mounted on the wall not on the kiln. Before these modifications, I had two melt downs due to the failure of my SSR because of heat build up in the controller box. Knock on wood...I've had no further problems! I often wonder why kiln manufacturers continue to mount controllers on the sides of kilns where they are exposed to high heat instead of a wall mounted unit, similar to the Skutt Clamshell controller.

Avery

Avery

So the Skutt Clamshell is a fiber insulation kiln with a wall mounted controller? If so, that is really one of the only commercial kilns that is actually designed for the glass fuser, not the kiln maker. Marty Daly's Genisis kilns (see Center de Verre) are also in this league.

I still think that the clamshell is not as good a design as a bell with stationary floor, but it is a far sight better than a top or front loading brick kiln. The clamshell design does have the smallest footprint possible though.