AGAIN - Leaving Kiln w/Bartlett 3 Controller

[candala]

Can those that have a Bartlett 3 Controller (my new Kiln is Jen Ken 14 inch, 120 Volt, 17 Amp) answer my previously posted question: Do you leave the house/studio while the kiln is on? Has anyone ever had the Bartlett 3 key controller fail and start to ramp up without stop? Thanks.

[Tony Smith]

Candala,

I recently saw a RampMaster 1 fail in the on position. In this case it was a controller glitch. Unplugging the power cord for a few seconds restored the controller to normal operation. After checking that the relays cycled properly for a few minutes (by watching the temperature rate of climb and listening for the frequency of clicking) the controller operated normally.

It is usually not the controller that fails, but the electro-mechanical relay or the SSR (solid state relay) which turn the electricity on and off to the elements. In the cases where the relay fails on, the controller is telling the relay to shut off (by cutting off the electricity to the relay), but the relay can't shut the flow of electricity off. This happens when SSR's fail. Electro-mechanical relays usually fail in the off position, but as with many things in life, that is not always the case.

Tony

[Phil Hoppes]

Sorry, it may not have looked like I was answering your question but you need to understand that all controllers work basically the same. Your controller may have a different computer for the front end but the "business" side of your controller are the relays that turn on and off the electricity to your elements. As Tony mentions above and I did in my previous post, ALL kiln controllers are subject to possible failure. This is why I got on my soap box about having backup systems to kill the kiln if it run's away.

For me, for the moment, I do all of my run's at night so yes, I'm asleep when my kiln is running. I usually start it in the late afternoon or early evening and check it a few times before I hit the sack. I've considered myself lucky for the moment, which is why I mentioned I will be installing backup kill circuits on all of my kilns. For me, I don't think it is a question of "if" just "when". My kiln sits in a very large garage with a very high ceiling so if it ran away it would have to cook for quite a long time to do any additional damage than what it would do to itself so I'm willing to take the risk for the moment. You need to evaluate this for yourself.

Phil

[Tony Smith]

There are many measures that can be added to increase the safety of kiln controllers, unfortunately, many of them require that you rewire your controller. For example, series power relays will virtually eliminate any potential problem from relays freezing in the on position, but will not prevent a runaway controller. A Kiln-sitter requires modification of the kiln but would be a reliable method for stopping a runaway condition. A separate temperature controller and thermocouple can be wired to a shunt trip circuit breaker in your power panel and will shut down power to the kiln in the event of a runaway.

It's also easy to convince yourself that it will never happen to you. I always fire overnight or when I'm at home. I have my controller alarm set 50° above my peak firing temperature and I have a baby monitor near the kiln with the receiver on my nightstand... although lately, I admit to getting complacent and leaving the receiver turned off. I try to always turn off the power switch when I leave the house as I don't want a power spike or momentary power failure to result in the kiln turning itself on.

I spoke with someone the other day who had started a firing in her hotbox and got distracted. As she was getting ready for bed (several hours later) she remembered that the kiln was on high. She found a glowing kiln and a puddle of glass, but thankfully no damage.

The key here is to try to be diligent and consistent about the way you operate your kiln, and to make sure there are no combustible materials under or near your kiln. Most kilns will only climb to a certain temperature and then they won't get any hotter. This temperature is governed by the size and type of element wire, the resistance of the element and the voltage supplied to the kiln. While it stresses the kiln, it would be reassuring to know what that temperature is for each kiln model. Perhaps the manufacturers have this information available for the asking. It would be comforting to know that my kiln can't reach the temperature where the kiln brick starts to break down

Tony

[Amy Schleif-Mohr]

You might want to talk with Marty at CDV, a board sponsor. He knows huge amounts of stuff about kilns and controlers and is willing to help. In the past he has told me that if my kilns are plugged in and turned off they can still start without me knowing it. I believe this is on Bartletts, I have a Rampmaster II and an Orton auto fire, both are Bartlett controlers.
He said that the power goes first to the relays then to the face of the controler. So, your controler may not be on but there is power to the relays/elements. So, it's a good idea to unplug your kilns if you are going on vacation or away for a while.

Amy

[gone]

You might want to talk with Marty at CDV, a board sponsor. He knows huge amounts of stuff about kilns and controlers and is willing to help. In the past he has told me that if my kilns are plugged in and turned off they can still start without me knowing it. I believe this is on Bartletts, I have a Rampmaster II and an Orton auto fire, both are Bartlett controlers.
He said that the power goes first to the relays then to the face of the controler. So, your controler may not be on but there is power to the relays/elements. So, it's a good idea to unplug your kilns if you are going on vacation or away for a while.

Amy

Right, Amy. That happened last year with my Bartlett. It had run a short program, cooled and I had taken the work out. About an hour later I began to hear the controller clicking again and it had started itself up again. It was only up to 150 degrees when I caught it, and since it was running the program, it wasn't going to have a meltdown. It hasn't happened since, but I've been better about unplugging things when I leave.

Els

[Tony Smith]

That's the first time I've heard of a controller turning itself on while the power switch is off. Since the power switch turns off the transformer that powers both the controller and the relays, there shouldn't have been any clicking of relays. I have heard and seen the Bartlett controllers turn themselves on after a power glitch with the power switch on though. That is why I always turn mine off. The older Rampmaster 1 didn't have a power switch so you would have to unplug it to turn the controller off...

Tony

[Amy Schleif-Mohr]

Tony,

You should talk to Marty at CDV then, because he specifically told me that power goes to the relays first then to the controler. So, the kiln could be firing without the contoler being on. That's why I always unplug my kilns if I'm going away for more than a day.

Amy

[Tony Smith]

Amy,

While I understand what he's talking about, I can't imagine it happening. People don't unplug their electric heat or electric stoves because they're leaving the house, but there is always power going directly to those contacts too. I will talk to Marty about it to see what his experience was.

Over time, plugging and unplugging your power cord may loosen the spring terminals that make contact with your plug. You might consider flipping off the circuit breaker instead.

Tony

[Amy Schleif-Mohr]

Tony,

I'm not that worried about my plug. I don't leave my house for more than a day very often and if it goes bad I'll just replace it.

Earlier I was just relaying what Marty said to me and he has much more experience with kilns than I do.

Amy

[gone]

That's the first time I've heard of a controller turning itself on while the power switch is off. Since the power switch turns off the transformer that powers both the controller and the relays, there shouldn't have been any clicking of relays. I have heard and seen the Bartlett controllers turn themselves on after a power glitch with the power switch on though. That is why I always turn mine off. The older Rampmaster 1 didn't have a power switch so you would have to unplug it to turn the controller off...

Tony

Tony, my controller doesn't have a power switch (I had to go check to be sure). It idles if you push the "stop" button, although I often leave it alone after it finishes the program and turns the kiln off, which is what I had done on the day it started itself. The power had gone out very briefly earlier in the day, so maybe there was another little power outage, although I do remember thinking about that and knowing that there were no blinking 12:00s on any of the appliances.
I really still don't know how it happened.

Els

[Tony Smith]

Sorry Amy. I didn't mean to sound contrary. I will talk to Marty tomorrow, to find out what his experience was.

Tony

[Tony Smith]

Tony, my controller doesn't have a power switch (I had to go check to be sure). It idles if you push the "stop" button, although I often leave it alone after it finishes the program and turns the kiln off, which is what I had done on the day it started itself. The power had gone out very briefly earlier in the day, so maybe there was another little power outage, although I do remember thinking about that and knowing that there were no blinking 12:00s on any of the appliances.
I really still don't know how it happened.
Els

Els,

Your experience agrees with mine. I've seen the Rampmaster 1 turn itself on, but only when there was power to the controller.

Tony

[Valerie]

My husband Jeff wired my kiln into a disconnect box with a 30amp breaker.
I turn my kiln on & off with the big switch on the box, along with dialogue
from "Young Frankenstein" It never has power unless it is firing a project.

[Ron Coleman]

Here's a link to the Bartlett Controller site.

http://www.bartinst.com/kiln.html

Select any controller and look at the topic "Complete Control Box Wiring". In my estimation this is not a good way to wire any electronic control device. There is no kill switch to stop the controller from starting the kiln if something should fail.

There needs to be a switch in the line with the fuse that powers the controller and for safety I'd add another on the controller output to the DC relay.

A "Power Disconnect Switch" to kill the mains is REQUIRED in industrial environments to totally disable any piece of electrical equipment that could injure anyone while servicing.

Ron

[Tony Smith]

Ron,

The Rampmaster II has a power switch that kills the power to the transformer thereby killing both the controller and the relays, but it doesn't interrupt the mains. I've added relay interrupt switches on my own kiln for my own safety while working in the hot kiln.

I'm not sure I agree about the industrial installation of equipment. From what I've seen, it's quite common to have power contactors or relays directly connected to the power feed with either a wall mounted knife switch, disconnect or in many cases, just a circuit breaker panel to act as your disconnect switch.

I'll take a look at a copy of the National Electric Code later today.

Tony

[Ron Coleman]

Ron,

The Rampmaster II has a power switch that kills the power to the transformer thereby killing both the controller and the relays, but it doesn't interrupt the mains. I've added relay interrupt switches on my own kiln for my own safety while working in the hot kiln.

I'm not sure I agree about the industrial installation of equipment. From what I've seen, it's quite common to have power contactors or relays directly connected to the power feed with either a wall mounted knife switch, disconnect or in many cases, just a circuit breaker panel to act as your disconnect switch.

I'll take a look at a copy of the National Electric Code later today.

Tony

A circuit breaker or knife switch is an acceptable means of disconnecting the equipment as long as it's within sight of the equipment. Around the corner and down the hall is not acceptable.

Ron

[Tony Smith]

Agreed.

[Phil Hoppes]

I've been looking quite a bit into controller design as I'm now building a kiln. Every one that I have seen so far has such an arrangement as shown on the design. I'm not arguing that an interruptor of some type should not be present, just that all of the designs I've seen have the mains come right into the hot side of the element relay's.

I would agree with the comments that they SHOULD have a breaker on the kiln and I would also add that I still think it is irresponsible that they do not have a redundant overtemp kill circuit. I just priced what I need to do from available off the shelf parts and it will cost just north of $300 to put a reliable overtemp circuit on my 24" Paragon. This is about a $2400 kiln so doing a way over kill job I can do it for about 10% of the cost. I know for a fact you could accomplish this with about $20 to $30 in real manufacturing cost so if you figure things tend to retail for about 4x the bill of material it could be offered to people for around $100. For the price of a commercial kiln this is cheap insurance and I think that a lot of customers would pay this if it were available to them.

BTW, my controller design will have main breakers with 10' of the kiln and on the control panel itself each element will have a separate breaker to allow me to individually turn on and off elements, in addition to a totally separate and redundant overtemp kill circuit.

Phil

[Bert Weiss]

I would never reccomend that any switches or relays be placed on a kiln. Place them on the wall near the kiln. Heat is the killer factor that makes things fail. Your kiln is much hotter than the wall is.