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Kiln Issue, Tripping Breaker


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Good Afternoon from the Deep Frozen Midwest,

 

I regularly check on one of my colleague's kiln, since I live very near the school she teaches at.  Normally this just involves me turning up the switches, and checking to make sure it has shut off. 

She contacted me yesterday to ask me to do so again, but also noted that it was not firing/ operating normally.  She said that on a recent, previous firing it was still running after nearly a day.  It was glowing red, but the cone didn't bend and trip the sitter.  She stopped the kiln and said everything seemed to turn out fine.  She reloaded the kiln, and it started fine, but when she went to check on it, the power light had gone off.

I went to check the kiln later, and she had turned it off, and pulled most of the work out.  The light still wasn't coming on,  with any of the switch settings, and the sitter was turned on.  I checked the breaker, and sure enough, it was tripped.

I set the sitter, turned on the kiln, and turned the bottom ring on.   No issues.  I turned the top ring on, and SPARKS.  The breaker kicked off again, and the switch panel smelled like welding.  I would imagine that the kiln didn't arc, when she started it, so it *was* running, and then kicked the breaker at some point in the firing. 

I let my colleague know about the issue, and said I'd go back and take a look this weekend.

The kiln has been working without an issue for the last several years.  I'm guessing there is an issue with the switch, or a loose wire that is arcing, but I'm far from an expert.

The kiln is a Skutt 231-18.  The elements actually look okay, which was surprising based on the firing that didn't fully finish. 

 

Thoughts/ Suggestions?

Edited by Benzine
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5 minutes ago, Mark C. said:

Turn off the power take the side box off and see what did the sparking (use the nose as well as eyes to find the issue) . Straight manuel kiln should be easy to spot the issue

Yeah, I was going to do that last night, but didn't have a screwdriver on me.  I'm guessing I will see some black marks in there somewhere. 

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Yep, look for the damage, if it arced it'll be pretty obvious.  Probably a connection that came off and touched the inside of the grounded control box somewhere.  Bring extra spade connectors, wire and a crimping tool just in case it's welded itself to something and you have to replace it.

 

Here in Seattle we are having a wind event mixed with about a foot of snow so far, and despite my kilns being 6 feet from the edge of the carport they are covered in snow.  I took the leaf blower to them but won't be running them for a while in case some of the powdered water got into them.

Edited by liambesaw
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22 minutes ago, liambesaw said:

Here in Seattle we are having a wind event mixed with about a foot of snow so far, and despite my kilns being 6 feet from the edge of the carport they are covered in snow.  I took the leaf blower to them but won't be running them for a while in case some of the powdered water got into them.

Yikes!

I have a former student, who lives out there.  She's posted some pics of the snow online. 

We have plenty of snow too, and it definitely aint going anywhere when the temps are this cold. 

Thanks for the kiln advice.  I actually have the exact same model of kiln in my basement, that was given to me forever ago.  I was always going to get it running, but came across a better one.  I was going to donate it to my District, because one of the elementary buildings is sans kiln, but they may end up getting a new one.  If they don't want it, I plan to convert it to a gas, salt or soda kiln, so it won't need the electrical components. 

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1 hour ago, liambesaw said:

Here in Seattle we are having a wind event mixed with about a foot of snow so far

Pretty sure I am not going out at 4 am to fire anything either. Got our snow already. Heat wave on the horizon though.

02A93177-B317-460D-B3C3-59919F1FA563.jpeg

Edited by Bill Kielb
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Lol yikes.  I'm generating a whole lot of nitrogen dioxide gas right now and didn't even think about how bad that might be since it's cold and snowing and my fume hood dumps right outside.  Hopefully my neighbors don't mind a little toxic orange snow.

Edited by liambesaw
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I haven't been in my studio for days,  it is just too cold to heat it up with my electric heater.   I think it is suppose to get down to negative 12 this week,  this part of Kansas isn't use to this severe of cold.   I have enough heat from the house to keep the pipes from freezing  in my studio.  The weather lady said we haven't had this kind of weather for thirty years.  I am trying to figure out which faucet to leave dripping all night.   Denice

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1 hour ago, neilestrick said:

-5F this morning, but it's supposed to get up to +5, so no worries!

Get out the "Spring" jacket!

We are supposed to get back up into the 20s, maybe even 30s a week from now.  That's going to feel like 50 compared to what we've had the past week.

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Rain here in the 40s-My assistant and i are unloading bisque kln and waxing pots today after lunch-most work is under a roof outside-should warm to 50 today

With one hand it will be a slow process-I really need to finished pots by next weekend .

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Well...  Found the problem.  No black marks, but two connections between the feeder wires and the elements were melted through.  One of the feeder wires was touching the red case, hence the sparks I saw, when I tried to turn the switch on.

So of the four connections in the top ring, it was the top most and bottom most that had melted through.

The feeder wires looked OK.

Would just the elements need replaced, or is this indicitive of another potential problem?

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I'm a bit surprised that they both melted through. It's not uncommon to have one connection fail, but two at the same time is odd. It could be that one of the connections had corroded and sent a shock through the whole circuit when it arced. I'd go ahead and replace all the feeder wires along with the elements since two of them took a hit. Also check the switch and make sure it didn't fry, too. And as long as you've got it apart, inspect the inter-box plugs, as those are a common weak link in the system. If they're not looking good, hard wire them rather than replace them.

I really dislike that type of ceramic insulators on the elements, since they can get pushed in and allow the wires to contact the metal body band. Was that the problem? Every time you change the elements they get pushed back in a little further into the brick. The T shaped insulators Skutt uses are much better, but it looks like the holes in the metal would be too big for those.  McMaster-Carr (and others) carry ceramic washers that you could put behind those insulators to push them out a bit further so they actually do the job.

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Looks like the crimped connector or whatever style it is corroded in half. Connectors are pretty much deigned to carry more current than the wire but if this had a crack or  some have a sight port the user can observe the embed depth of the wire.  Less metal means less area to carry current means less cooling meaning more warming. More warming leads to higher random electron movement means more resistance at the warm junction means further heating ............... thermal runaway. 

Wires will physically try to move when a large load is applied due to the field. The larger inrush, the bigger the movement. I can take folks to elevator banks without soft start equipment and they can literally here the wires jump and slap the pipe during high current startup. I can then show sections that have been replaced where the wire finally wore through a spot after slapping against the inside of the pipe for thirty years and fused to the pipe.

Small loads, small forces but likely enough along with gravity to help separate your corroded connector when weakened enough by corrosion.

I would guess wear and tear and replace with something better from today’s available connections. Leaving a bit longer pigtail will get this further away from kiln heat, more in cooler surrounding air and can improve longevity significantly if it can be done in a safe way that will not arc or short against something.. I would  cut the wire back a bit especially if it has signs of heat damage to get to clean new wire. Skutt used to send crimps that were big enough for two wires. When using for single wire connection they would specify to strip extra and fold over for an adequate connection before crimping really tight.

I am with Neil check all that you can. Thermal scanning connections  has helped detect many of these before failure,  That would include switches, plugs, all junctions, even cord ends. Where there is heat there is voltage drop, wasted wattage and of course more buildup of more heat as the junction resistance slowly rise.

Edited by Bill Kielb
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Thats the same style of innards that i had rebuilt last year-same older style skutt stuff

Buy your elements from Skutt and the newer style ceramic insulators come with them and they fit fine.Crimps come with the elemnets as well .I'm going to use the brass screw type  wire connecters  that Min posted` a photo of from Euclids next time (actually  later this spring as I'm working on something for skutt and they wanted some old parts of mine)

Those plugs are no longer available so I cleaned mine and used copper/shield on the slots to keep them running cooler.Hard wiring is fine but I seem to be always wanting it apart in sections to access it in it 3 sided box it lives in.

I agree new feeder wires and new elements-mine melted off like your one year ago on top element as well.When it all apart clean all conections so  thaqt are brassy clean.

Here is what I did in early 2020 on my old skutt

https://community.ceramicartsdaily.org/topic/21326-skutt-1227-rebuild/?tab=comments#comment-171678

 

Edited by Mark C.
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Easiest way I am aware of is thermally in operation. Old standby again in operation is measure the voltage drop across the connected switch. If it’s supposed to act like a continuous piece of wire then no voltage drop. As the connection degrades, oxidizes etc. there will be voltage drop. Measuring the voltage drop across these contacts while fully loaded will, tell you their condition.  Acceptable voltage drop would be zero to probably no more than a few tenths of a volt. Typical maximum allowable voltage drop across relays and switches has traditionally been 300 mv. Or 0.3 volts.

Here is an early vid, shows some uses of thermometer. https://youtu.be/c7HZlAn4nZw

 

Edited by Bill Kielb
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Would it be better to go directly through Skutt, rather than a general ceramic supply company?

The supplier I use for most of my clay classroom materials doesn't even list elements for this type of kiln, but they say they can get them for nearly any model.  Buuut since I also need a couple bricks and feeder wires, I probably won't use them.

I only ask, because I will likely have to add/ have approved either Skutt or another supplier to our purchase order system.

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14 hours ago, Mark C. said:

Thats the same style of innards that i had rebuilt last year-same older style skutt stuff

Buy your elements from Skutt and the newer style ceramic insulators come with them and they fit fine.Crimps come with the elemnets as well .I'm going to use the brass screw type  wire connecters  that Min posted` a photo of from Euclids next time (actually  later this spring as I'm working on something for skutt and they wanted some old parts of mine)

Those plugs are no longer available so I cleaned mine and used copper/shield on the slots to keep them running cooler.Hard wiring is fine but I seem to be always wanting it apart in sections to access it in it 3 sided box it lives in.

I agree new feeder wires and new elements-mine melted off like your one year ago on top element as well.When it all apart clean all conections so  thaqt are brassy clean.

Here is what I did in early 2020 on my old skutt

https://community.ceramicartsdaily.org/topic/21326-skutt-1227-rebuild/?tab=comments#comment-171678

 

Ooooh, those brass connectors are pretty slick!  Are those meant to be reusable?  I only ask, because the L&L I have in my classroom included all new bolts and washers, with the new elements, despite the fact the old ones looked fine.

What is that Kopr-Shield stuff exactly?

That kiln restore looks terrific.  Too bad their aren't "Car Show" like events for kilns.  "Hey man, you see that restoration Mark C. did?  That thing looks cherry!"

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32 minutes ago, Benzine said:

Ooooh, those brass connectors are pretty slick!  Are those meant to be reusable? 

Don't know if they are meant to be reusable but that's what I've been doing. The weak link is where the connection is made, if for any reason there is a malfunction and the element is still good you can often move the connection further up the lead and make a new connection. Far easier than if crimp on connectors were used.

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8 minutes ago, Min said:

Don't know if they are meant to be reusable but that's what I've been doing. The weak link is where the connection is made, if for any reason there is a malfunction and the element is still good you can often move the connection further up the lead and make a new connection. Far easier than if crimp on connectors were used.

I never understood the crimp connectors.  You have to shorten the feeder wires each time.  I'm guessing the assumption is, that by the time that the feeder wires were too short, it would be time to replace them anyway,  simply due to age.

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11 minutes ago, Benzine said:

I'm guessing the assumption is, that by the time that the feeder wires were too short, it would be time to replace them anyway,  simply due to age.

Exactly. They are problematic for other reasons, though. Like in the case of the kiln you're working on, there's a chance that a non-crimp connector would have allowed you to make a new connection to the elements, rather than having to replace the element. I've worked on a lot of old kilns that just used stainless nuts/bolts/washers as connectors. Make a loop in the element end, put the bolt through it with a washer on each side, and connect the feeder wire with a high temp ring terminal. Basically the L&L method but without the ceramic block holding everything together. Pretty easy to do, and inexpensive. One thing I like about the L&L setup is that if the element fries at the bolt connection, you've still got enough element end to make a new connection.

The brass connectors can be reused as long as you clean them up, as they do tend to corrode over time. A little WD-40 and a wire brush will get them looking new again. Make sure to clean out the inside of the tube.

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