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mgtmeehan

Cracked floor on Duncan Pro 1029-2

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I just acquired an old Duncan Pro 1029-2.  The kiln works fine, but when we moved it to my place, I noticed the metal straps on the bottom were corroded... after putting it down in its new home, I removed the shelf that had been on the floor and discovered that the floor had big cracks.  it is pretty obvious that the corroded metal base strips were not able to support the floor. The kiln had been in the seller’s garage, on a tower of large cinder blocks.  I am thinking that her garage may have flooded, and that she put the kiln up higher to prevent future disasters. I really don’t want to have to turn the kiln over to deal with the floor.  Can I repair the firebricks in place? Or is that just postponing another disaster?   Any help offered would be greatly appreciated. Thanks!

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Edited by mgtmeehan
typo

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The cracks don't really have much to do with the metal straps. If the floor wasn't sitting evenly on its stand, then the weight of the walls and the pots caused it to bend and flex and eventually crack. Trying to mortar those old bricks back together will be a waste of time. Your best bet is to tighten up the strap, put a piece of sheet steel under the floor to support it, and make sure it is evenly supported.

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Ok, thanks so much for your prompt reply.   I was thinking of getting a large  stand like the Paragon 12” high one, so I could put a vent system under the bottom of the kiln.   Do you think the upper metal shelf of that kind of stand could support the cracked floor? Is trying to vent through this cracked bottom a dumb idea? The kiln is in my garage, and I have an old Paragon high fire 88 as well.  I have opened the garage door whenever I fired the smaller kiln, but was thinking of venting through the wall now that I have the larger kiln as well.   Right now I have the Duncan on  4 sets of 12x12 concrete slabs, 2 deep (4” off the floor).  I placed the slabs so that there is a space between them.  

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Just a note, these manifolds or pickups can be installed at the bottom of the kiln along the side (see pic below) and in the picture of your kiln there are no elements in the bottom so if you can tighten the band and if it is fully supported underneath then you certainly can surface route all these cracks and Neatly kiln patch them just to keep this thing semi hermetic for lots of firings.

I would not remove the bottom or lift  the kiln or patch  a whole bunch until after the band was tightened and I could get something fully under the bottom though.393F0295-31CE-4597-8C0B-51565BD8E2D8.jpeg.3446cab37cb824064f9b7cf0cea981b7.jpeg

just a thought

Edited by Bill Kielb

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Thank you!  I had not known about a side vent possibility.  I will go about the floor stabilizing process very slowly and carefully.  I cannot upload any more photos, to show more detail,  due to the limits on this blog... maybe I need to reduce the photo resolution to a lower level? 

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Do you have a metal salvage yard in your area,  you might be able to find a piece of metal just the right size.  It could even have a hole cut in the center already.    I live in Wichita, KS  where the aircraft is the main industry  so we are spoiled  when it comes to having places like this to shop at.    My husband just had a show car reupholstered,  we shopped at four salvage places for the leather.  They have piles of leather that are overages from the aircraft companies,  we couldn't find the right color.  So we spent $400 a hide and it was only $50 a hide at the salvage.  We didn't get to save any money this time but there is always the next project.  Denice

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I prefer the side venting with the Orton and Skutt vents because the connection is screwed to the kiln and can't be moved. Mounting underneath uses a spring-loaded rod to push the cup against the floor, which can easily be moved out of position if you bump the duct. Skutt, Orton, and L&L Vents can all be side mounted.

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12 hours ago, mgtmeehan said:

Ok, thanks so much for your prompt reply.   I was thinking of getting a large  stand like the Paragon 12” high one, so I could put a vent system under the bottom of the kiln.   Do you think the upper metal shelf of that kind of stand could support the cracked floor? Is trying to vent through this cracked bottom a dumb idea? The kiln is in my garage, and I have an old Paragon high fire 88 as well.  I have opened the garage door whenever I fired the smaller kiln, but was thinking of venting through the wall now that I have the larger kiln as well.   Right now I have the Duncan on  4 sets of 12x12 concrete slabs, 2 deep (4” off the floor).  I placed the slabs so that there is a space between them.  

The taller the stand, the more difficult it is to load the bottom of the kiln.

A kiln stand will not support that cracked floor unless the top of the stand is full sheet metal, not just a frame. As far as I know, L&L is the only one who makes a stand like that in a regular stand. However I believe most of the rolling stands on the market do have a full top.

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This has to be the best help blog ever!  Thank you all for your information and suggestions.  All are greatly appreciated. 

Denice, thank you for the heads up re: salvage yards.  I am sure to find one around here... the Naval Flight Base is around the corner. :-). And your find on the leather was awesome,  off topic, but I also make handbags, and have shied away from leather due to the investment, even though my old beast of a sewing machine can handle it.  

Neil, I think the sheet metal, if I can find some, should work.  The kiln stand I was looking at is on rollers, and has a full metal shelf top,  It is pricey, though, understandably.   However, I would need a step stool to reach i side the kiln... at 5’4” I barely reach the boom now, and I don’t want to lean on the top edges of the walls to get inside. 

Bill, thank you for the side vented photo, also.

One more issue... the kiln was hardwired to the wall at its last home.  I have a completed wiring receptacle, emergency shutoff, and extra circuit breakers already.  Is it acceptable to have an electrician fit the cord with a plug that matches the receptacle, or do I need to hardwire the kiln?  The receptacle is a NEMA 14-50.  The old Paragon kiln I have was fitted withe the same plug, so my electrician put up the two setups the same way, when it was first done. 

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You can install a plug as long as it is rated equal or greater than the load. Your electrician will need to match the breaker of the circuit to the kiln requirement and check that the wiring from the breaker is proper size or over sized for the new load. Hard wired kiln connections are better than plugs.

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Hard wired connections tend to not corrode as fast as plugs, however I've seen a lot of melted fuses on hard wired kilns, too.

If you hard wire it, make sure the cord is long enough to be able to work in the control box. I run into a lot of kilns where I can barely open the box because the cord is short. And since it can't be unplugged, it's a real hassle. It's also nice if it's wired into a fused disconnect.

If you do a plug, don't worry, just inspect it regularly for corrosion.

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Thanks very much, Bill and Neil.  

Each kiln already has its own 14-50 receptacle, already installed on the wall behind, above, and to the right of each kiln.  Each receptacle is wired into its own fuse disconnect box, which is located behind, above and to the left of each kiln.   In turn, each fuse box is wired into a circuit panel, to a circuit breaker that is a double  50 amp  breaker (100 amps).  Each kiln has its own doubled 50 amp breaker (100 amps per kiln).  We have two separate circuit panels, and one kiln is wired into each one of the panel boxes.  

The cord on the Duncan is not very long, so I think we will do the 14-50 plug.  I have that setup on the Paragon high-fire 88, and the electrician who installed the whole thing wanted to be sure that all the connections could handle more amps than what any attached kiln data panel designated. 

 The Paragon draws 38 amps.  The Duncan is listed at 45 amps.  I do not intend to ever fire them simultaneously. 

I really appreciate all your advice and suggestions.  I have learned a lot, here... ready to learn more. :-). Thanks!

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Hmm, work looks all good from what can be seen, hopefully they are not both on the same breaker though, just mentioning. Lots of greenfield, not sure why, maybe it was the old direct connection whip. Generally flexible connections are limited to 6 feet or less.

I see tandem breakers in your panel so older service, sorry I feel your pain.

epoxy floor - nice touch! Textured wall, southern climate.

might need some ventilation, don’t see any.

Edited by Bill Kielb

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I know nothing about electricity...lol... so was unaware of the outdatedness of the service... the breakers for the kilns were just done about 2 months ago... but the kilns are not on the same breaker, at least.  Each kiln has its own, and each breaker is on a separate panel.  The house is 20 years old.  Have no idea what greenfield is, but I am guessing you are referring to lengths of cable?  The cord and plug on the Paragon are 6 feet.  The cord with exposed end, on the Duncan, is barely 6 feet.  I need to rotate the Duncan kiln more to the left, to get the cord to reach the receptacle.  That will be tricky...lol...

 Yes, ventilation is being considered.  There is a big window on the side, and the garage door... but I am looking at venting systems.  They look pretty pricey... but I will do my homework.  I have fired the Paragon a few times, to Cone 6, with the garage door open. 

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1 hour ago, mgtmeehan said:

I know nothing about electricity...lol... so was unaware of the outdatedness of the service... the breakers for the kilns were just done about 2 months ago... but the kilns are not on the same breaker, at least.  Each kiln has its own, and each breaker is on a separate panel.  The house is 20 years old.  Have no idea what greenfield is, but I am guessing you are referring to lengths of cable?  The cord and plug on the Paragon are 6 feet.  The cord with exposed end, on the Duncan, is barely 6 feet.  I need to rotate the Duncan kiln more to the left, to get the cord to reach the receptacle.  That will be tricky...lol...

 Yes, ventilation is being considered.  There is a big window on the side, and the garage door... but I am looking at venting systems.  They look pretty pricey... but I will do my homework.  I have fired the Paragon a few times, to Cone 6, with the garage door open. 

Yes vents expensive and in Pensacola (love Florida weather) you could use all you could get. Downdrafts will not remove any real heat to speak of. Most hoods will help but still fall short at 80 degree make up air.  Looks like you will have some firing firing fun in your future!

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Thank you, liambesaw and Bill.  Hmmmmm... the electrician who did the work admitted he had never hooked up a kiln before, and he didn’t know anyone around here who had.  I gave him all the literature I had on setting up a kiln, before he started, then he said he knew what to do, and would make sure it was all  safe.  

Maybe, because my info was specific to the old Paragon, he followed the instructions to a T, but if the instructions were old, then his work might reflect that.  At least I know that the amperage is adequate, and the kilns each  have emergency shut-off boxes.  

I am still researching venting. 

Hmmmmm.... if I ever have a code inspection, this will be interesting. Thanks for the info, and encouragement. :-)

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Technically, the Duncan should be on a 60 amp breaker, not a 50. Code calls for kilns to be on a breaker that is 25% greater than the draw of the kiln. At 45 amps, that comes out to 56, so you go to a 60. I wouldn't go changing anything at this point, though, unless the 50 flips while firing.

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Ok, thank you, Neil.  So the breaker I have, which is 2 fifties together, is not sufficient?   Are you saying I would need a single breaker with a minimum of 60, instead, and preferably even larger?.   Is the tandem breaker that I have really just one "fifty"with a backup next to it?  

Bill, is that what you meant when you said "I feel your pain?"' I didn't have any pain until now...lol...     I also looked up etm conduits vs. "greenfield", not sure why the electrician chose the  flexible vs  the rigid.

Thank you both for your help.

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What Liam said is correct. It is a 2-pole-50-amp breaker. Two 120 volt legs to make the 240 volts needed for the kiln, but it's only 50 amps, not 100. Code says 25% greater than the draw but not more than 50% greater. Both kilns would fit that if you end up needing to change it to a 60. Leave it for now, though.

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Wow.  THANK YOU.  I just learned a lot.  Sometimes it's hard to know what questions to ask, when you don't know very much.  I really appreciate your answers!   I will get 60  amp breakers for each setup,.   And I thought the power was more than enough.  Education certainly helps, and you are both great educators. :-)

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As a former electrician Your  50 amp breakers are likely just fine and protect your 50 amp rated receptacle nicely.  If you are worried, check the breakers periodically during a firing and make sure to the touch they are not heating up excessively as in hot to the touch, I doubt they will.  The tandem breakers are the ones that are actually two breakers in one space. Pretty popular at one time allowing one to put more circuits in a panel that has run out of available spaces. The picture shows the 15 amp bedrooms on this style breaker which fits two breakers in one slot. It tells me your panel is maxed out for positions and someone installed the tandems to make room for ...........the kilns, maybe. Quite common for older panels hence the I feel your pain joke.  I Have run out of available positions many times over the years.

everything is reasonably neat and yes the  flexible conduit could be EMT but basically looks decent. Even the tandem breakers, just a way to get some room in the panel.

For various safety reasons I prefer the breaker match or be less than the wire and receptacle rating so those items are protected. The wire on the other hand usually should be rated higher than the maximum load usually for voltage drop reasons,  As a result the breaker will protect everything nicely.

There is a 25% rule that allows increasing the breaker size which in Kiln land puts everything at 60 amps yet 50 amp receptacles are super common and most recommended and 60 amp receptacles cost more and 60 amp plugs a bit of an issue as well. So it is common to see 50 amp receptacles suggested even though the machine was tested and certified to 60 amps catastrophic short.  Additionally newer  breakers  today are moving toward continuous rated,  so upsizing things is becoming a thing of the past.

lets put it this way, the breaker should be the first thing to trip rather than the wire melting or receptacle melting. Your electrician likely did fine.

Edited by Bill Kielb

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Thank you so much for the detailed reply.  I was getting nervous about even attempting a glaze fire at Cone 6 in the bigger Duncan.  I don’t have a load yet anyway, and my smaller Paragon has done those successfully, so I should be ok.  I will do a test fire first, anyway... after I stabilize the floor.  Thanks again  for taking the time to write such an informative response, it is very much appreciated.  I won’t scold my electrician...lol... he did what he could with what was available, I am sure.  Thanks! 

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