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#21 Sojourner

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Posted 30 December 2011 - 03:48 AM

Well on looking into it some more, I found that there are actually several smaller kilns (but larger than the teensy tabletop models) that can be plugged into either a dryer or range outlet. The only other one that I've identified so far that's in the 2.5 cu ft and up range, though, is a Paragon, which is apparently sold only by The Big Ceramics Store online. The Paragon Biggest Little Kiln is rated at 28A, fires to cone 8, and has a capacity of 2.9 cu ft. It comes with a NEMA 6-30 plug. I've seen this alternately described as a dryer plug, and also as a range plug. The Big Ceramics Store describes this as a dryer plug. They state this should be hooked up to a 30A breaker, but personally I'm not comfortable with that - YMMV. A breaker should exceed its load by at least 10%, which means you wouldn't normally put over 27A on a 30 A breaker. This may not sound like much, and 9 times out of 10 you'd probably be right, but keep in mind that some building codes limit total circuit load to 80% or even 75% of rated amperage on a breaker. Remember that the further you push into the upper performance range, the more stress you put on the system. Ultimately, you CAN do this; but I wouldn't.

In contrast, the L&L Liberty Belle operates at 24A, which is well within the safe operating range of a 30 A fuse. It also fires to cone 10, though if you run it up there very often you will significantly shorten the life of the elements. It comes with a NEMA 14-30 plug, which definitely is a dryer plug. It replaces the older 10-30 which was in common use prior to 2000.

And there is the problem with these kilns. Older houses will most likely be wired with 3-wire 10-30 outlets instead of the newer 4 wire 14-30 outlets, but these kilns will be wired for the newer outlets. You can't just switch outlets, either, because there's a physical (and electrical) difference in the wire used. Also, if your outlet is more than 40' or 50' from the breaker box, you will need to go up a level for the wire, eg this kiln requires a minimum of 10 g wire but if the run from the breaker box is longer than that, you will need to run the larger diameter 8g wire. Another thing you can do to reduce stress on the system and reduce overheating in the wiring is to run the wire across the surface in metal conduit instead of pulling it through the walls. Not a big deal if you are installing this at or near the breaker box, but it makes a difference if there's a long run. The wire will run cooler in surface mount metal conduit, and cooler wire also means less expense since you're not paying for the power that would otherwise be wasted generating heat.

I've seen some really really HORRIBLE ideas about how to handle this situation in various forums across the Internet and all I can say is, DO NOT CUT CORNERS with your electrical wiring. I've seen people state that you can just switch the outlets or the plugs, with various schemes for how to get around the 3-wire to 4-wire problem. Well, maybe some of those schemes would work, sort of, but no matter how you slice it, this sort of jerry-rigging WILL void your home owner's insurance. Also, it's your life. Just don't do it.

Now some houses built prior to 2000 and after about 1995/1996 may have the 10-30 outlets (you can google to see what these outlets look like) but were actually wired in anticipation of the upgrade to the new standard 14-30 outlets - they knew this change was coming but nobody knew for sure when it would be implemented. So there's a chance that you could have the wrong outlet but the correct wire in the wall. You won't know for sure until somebody removes the outlet cover and takes a look at what's in there (with the power shut off, of course). It's easy to switch the cord on the back of the dryer to upgrade to the new outlet, if that's all you need to do. But actually rewiring the entire circuit - it'd be easier and smarter to just run a totally new circuit for the kiln, if you've got the spare amperage.

Another problem is that these types of plugs are not suited to constant plugging/unplugging - this will prematurely wear the connections on both the kiln AND the dryer. Probably there's some sort of switch out there that you could use to switch the load on the circuit between the dryer and the kiln, similar to a 30A dual pole dual throw 240v AC switch, which looks like a light switch except it has 3 positions: Load 1 (Dryer) - OFF - Load 2 (Kiln). HOWEVER THIS IS NOT A SOLUTION for this application because I'm almost positive these switches are NOT rated for a continuous load like a kiln. Another possible solution would be a full-on transfer box, wired to switch one power source (the supply from the breaker box) between 2 loads (dryer or kiln), but these are mighty pricey - I looked one up (a 100A transfer switch, which is admittedly way overkill for this application) and it was $750. A 30A transfer switch I found online was listed at $200, and I'm not sure it could be wired up for this application. It's possible there's an appropriate solution somewhere in between a $30 30A DPDT 240v AC switch and a transfer switch or double throw safety switch, but I don't know what it is, and it will still require SOME wiring, though nowhere near as much as if you have to run a totally new circuit. This is NOT, btw, the answer to the 3-wire vs 4-wire problem; you still need the appropriate wire run from the breaker box to your kiln, whether it goes through a switch first or not.

So, these kilns might be a solution for some people, but a smaller set of people than you might think at first glance. There just is no such thing as a plug-'n-play kiln, unfortunately.

Other things to consider are venting; fire safety (you can't install one of these on carpeted or wooden flooring; I don't know if the fire retardant safety bases for wood burning stoves are sufficient unto this task); proper clearance from walls etc., also related to fire safety; possible contamination of food prep areas (I wouldn't operate one anywhere near the kitchen, not even if it's vented); temperature - kilns can get very hot and if you put this in an enclosed or semi-enclosed area you could quickly exceed the 100F to 110F environmental temp that could cause the kiln to auto-shutdown for safety reasons. Also having it actually IN your living area could significantly increase your cooling bills in warm months, increasing the overall cost to you of firing.

Happiest solution would be if you could put it in a garage and if your breaker box is right there nearby. Assuming you have the spare amperage (most houses have either 100A or 200A service, add up the total amperage of all currently installed breakers, subtract that from your service, that's your spare amperage) it's not difficult to install a 30A 240v breaker and run wire in surface conduit a few feet to where your kiln will sit. That's really your cheapest solution. Of course, if you can do that, there's no real advantage to the smaller kiln other than space saving, or if your spare amperage precludes installing a 50A or higher breaker. (eg you have 100A service but have already used 70A worth; if you've used more than 70A out of 100A, you can't even install the 30A breaker; likewise, your service is 200A but you already have 170A of breakers installed, leaving 30A free, you couldn't install a larger breaker for a bigger kiln).

When I built my house, I ran 100A service to the house but 200A service to the barn because all my appliances (except the fridge) were going to be propane, and I wanted to be able to run all my power equipment from the barn. Had I wanted 200A service in both places, the power company would have required me to buy, install, and pay monthly fees for a second meter. Given that there is a minimum monthly fee for having the meter whether or not you're actually using power, I really didn't want to do that. The minimum fee was $15 at the time, but I think that's up to $30 or more by now. Fees like that just keep going up, but our income seldom rises to match it. At least I knew mine wouldn't, LOL!

Also, all my interior wiring was to be run in surface mount conduit for increased efficiency and safety - you can't have a fire smoldering in the walls for days or weeks if your wiring isn't buried in the walls to start with. Most modern houses are built with 200A service these days, but some (much) older houses don't even have 100A service. If you're rural, outbuildings may be underpowered or separately powered. It's important to check and see what you've got.

There are probably other things I've not thought of. Sadly - no plug-'n-play kilns!

#22 Pres

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Posted 30 December 2011 - 08:26 AM

Well on looking into it some more, I found that there are actually several smaller kilns (but larger than the teensy tabletop models) that can be plugged into either a dryer or range outlet. The only other one that I've identified so far that's in the 2.5 cu ft and up range, though, is a Paragon, which is apparently sold only by The Big Ceramics Store online. The Paragon Biggest Little Kiln is rated at 28A, fires to cone 8, and has a capacity of 2.9 cu ft. It comes with a NEMA 6-30 plug. I've seen this alternately described as a dryer plug, and also as a range plug. The Big Ceramics Store describes this as a dryer plug. They state this should be hooked up to a 30A breaker, but personally I'm not comfortable with that - YMMV. A breaker should exceed its load by at least 10%, which means you wouldn't normally put over 27A on a 30 A breaker. This may not sound like much, and 9 times out of 10 you'd probably be right, but keep in mind that some building codes limit total circuit load to 80% or even 75% of rated amperage on a breaker. Remember that the further you push into the upper performance range, the more stress you put on the system. Ultimately, you CAN do this; but I wouldn't.

In contrast, the L&L Liberty Belle operates at 24A, which is well within the safe operating range of a 30 A fuse. It also fires to cone 10, though if you run it up there very often you will significantly shorten the life of the elements. It comes with a NEMA 14-30 plug, which definitely is a dryer plug. It replaces the older 10-30 which was in common use prior to 2000.

And there is the problem with these kilns. Older houses will most likely be wired with 3-wire 10-30 outlets instead of the newer 4 wire 14-30 outlets, but these kilns will be wired for the newer outlets. You can't just switch outlets, either, because there's a physical (and electrical) difference in the wire used. Also, if your outlet is more than 40' or 50' from the breaker box, you will need to go up a level for the wire, eg this kiln requires a minimum of 10 g wire but if the run from the breaker box is longer than that, you will need to run the larger diameter 8g wire. Another thing you can do to reduce stress on the system and reduce overheating in the wiring is to run the wire across the surface in metal conduit instead of pulling it through the walls. Not a big deal if you are installing this at or near the breaker box, but it makes a difference if there's a long run. The wire will run cooler in surface mount metal conduit, and cooler wire also means less expense since you're not paying for the power that would otherwise be wasted generating heat.

I've seen some really really HORRIBLE ideas about how to handle this situation in various forums across the Internet and all I can say is, DO NOT CUT CORNERS with your electrical wiring. I've seen people state that you can just switch the outlets or the plugs, with various schemes for how to get around the 3-wire to 4-wire problem. Well, maybe some of those schemes would work, sort of, but no matter how you slice it, this sort of jerry-rigging WILL void your home owner's insurance. Also, it's your life. Just don't do it.

Now some houses built prior to 2000 and after about 1995/1996 may have the 10-30 outlets (you can google to see what these outlets look like) but were actually wired in anticipation of the upgrade to the new standard 14-30 outlets - they knew this change was coming but nobody knew for sure when it would be implemented. So there's a chance that you could have the wrong outlet but the correct wire in the wall. You won't know for sure until somebody removes the outlet cover and takes a look at what's in there (with the power shut off, of course). It's easy to switch the cord on the back of the dryer to upgrade to the new outlet, if that's all you need to do. But actually rewiring the entire circuit - it'd be easier and smarter to just run a totally new circuit for the kiln, if you've got the spare amperage.

Another problem is that these types of plugs are not suited to constant plugging/unplugging - this will prematurely wear the connections on both the kiln AND the dryer. Probably there's some sort of switch out there that you could use to switch the load on the circuit between the dryer and the kiln, similar to a 30A dual pole dual throw 240v AC switch, which looks like a light switch except it has 3 positions: Load 1 (Dryer) - OFF - Load 2 (Kiln). HOWEVER THIS IS NOT A SOLUTION for this application because I'm almost positive these switches are NOT rated for a continuous load like a kiln. Another possible solution would be a full-on transfer box, wired to switch one power source (the supply from the breaker box) between 2 loads (dryer or kiln), but these are mighty pricey - I looked one up (a 100A transfer switch, which is admittedly way overkill for this application) and it was $750. A 30A transfer switch I found online was listed at $200, and I'm not sure it could be wired up for this application. It's possible there's an appropriate solution somewhere in between a $30 30A DPDT 240v AC switch and a transfer switch or double throw safety switch, but I don't know what it is, and it will still require SOME wiring, though nowhere near as much as if you have to run a totally new circuit. This is NOT, btw, the answer to the 3-wire vs 4-wire problem; you still need the appropriate wire run from the breaker box to your kiln, whether it goes through a switch first or not.

So, these kilns might be a solution for some people, but a smaller set of people than you might think at first glance. There just is no such thing as a plug-'n-play kiln, unfortunately.

Other things to consider are venting; fire safety (you can't install one of these on carpeted or wooden flooring; I don't know if the fire retardant safety bases for wood burning stoves are sufficient unto this task); proper clearance from walls etc., also related to fire safety; possible contamination of food prep areas (I wouldn't operate one anywhere near the kitchen, not even if it's vented); temperature - kilns can get very hot and if you put this in an enclosed or semi-enclosed area you could quickly exceed the 100F to 110F environmental temp that could cause the kiln to auto-shutdown for safety reasons. Also having it actually IN your living area could significantly increase your cooling bills in warm months, increasing the overall cost to you of firing.

Happiest solution would be if you could put it in a garage and if your breaker box is right there nearby. Assuming you have the spare amperage (most houses have either 100A or 200A service, add up the total amperage of all currently installed breakers, subtract that from your service, that's your spare amperage) it's not difficult to install a 30A 240v breaker and run wire in surface conduit a few feet to where your kiln will sit. That's really your cheapest solution. Of course, if you can do that, there's no real advantage to the smaller kiln other than space saving, or if your spare amperage precludes installing a 50A or higher breaker. (eg you have 100A service but have already used 70A worth; if you've used more than 70A out of 100A, you can't even install the 30A breaker; likewise, your service is 200A but you already have 170A of breakers installed, leaving 30A free, you couldn't install a larger breaker for a bigger kiln).

When I built my house, I ran 100A service to the house but 200A service to the barn because all my appliances (except the fridge) were going to be propane, and I wanted to be able to run all my power equipment from the barn. Had I wanted 200A service in both places, the power company would have required me to buy, install, and pay monthly fees for a second meter. Given that there is a minimum monthly fee for having the meter whether or not you're actually using power, I really didn't want to do that. The minimum fee was $15 at the time, but I think that's up to $30 or more by now. Fees like that just keep going up, but our income seldom rises to match it. At least I knew mine wouldn't, LOL!

Also, all my interior wiring was to be run in surface mount conduit for increased efficiency and safety - you can't have a fire smoldering in the walls for days or weeks if your wiring isn't buried in the walls to start with. Most modern houses are built with 200A service these days, but some (much) older houses don't even have 100A service. If you're rural, outbuildings may be underpowered or separately powered. It's important to check and see what you've got.

There are probably other things I've not thought of. Sadly - no plug-'n-play kilns!


When I had my wiring in the garage changed, an electrician put in my new service, and I had the meter put on the outside. I put in the wiring, inspected by the electrician. I did make the mistake of only putting in 100 amp service at the time, but will probably put in 200 soon. I have another kiln-used that I bought from the school district I worked in. I was familiar with the kiln, and it had only been fired twice. It is an Amaco. I am not real happy with it, but the fact that it was cheap, and in new condition worked out well. I also have an L&L that I can say nothing but good about. The element holders are a great boon for someone that fires constantly like in a school situation. Changing elements is pretty much a breeze. I had 2 L&L when teaching over 30 years.

Simply retired teacher, not dead, living the dream. on and on and. . . . on. . . .                                                                                 http://picworkspottery.blogspot.com/


#23 teardrop

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Posted 30 December 2011 - 10:10 AM

Very informative post, sojourner. Many thanks.

What about voltages? I am looking at buying a kiln myself.....so I've been taking note of the set up at the college I take classes at. They have 2 L & L's...

Kinda freaked me out when I saw that the smaller kiln is a 208 volt...the larger a 240 volt.... but get this...there's only one outlet..and obviously...it isn't BOTH voltages. I didn't take the cover off the electrical box to see what voltage it is..but needless to say...one of the kilns isn't getting the juice it should one way or the other. I have read that many schools are 208V ut I'll have to wait til they open in Jan to check it out further.

I don't know if the teacher knows about this difference in voltages or not. she was already gone for Christmas break when I noticed it.

Thoughts? I doubt they will run a new service...being that we are unplugging/plugging in whichever kiln we need at the present time... but you sound very knowledgeable on all of this so I figured I'd take the liberty and ask what the dangers/trouble might be in continuing to run these kilns in such a manner.

also....Do the digital controllers adjust for this voltage difference and will the kiln still fire at the proper temp?

thanks for any insight

teardrop
Be who you are and say what you feel, because those who mind don't matter and those who matter don't mind. Dr. Seuss US author & illustrator (1904 - 1991)

#24 Sojourner

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Posted 30 December 2011 - 11:00 AM

Very informative post, sojourner. Many thanks.

What about voltages? I am looking at buying a kiln myself.....so I've been taking note of the set up at the college I take classes at. They have 2 L & L's...

Kinda freaked me out when I saw that the smaller kiln is a 208 volt...the larger a 240 volt.... but get this...there's only one outlet..and obviously...it isn't BOTH voltages. I didn't take the cover off the electrical box to see what voltage it is..but needless to say...one of the kilns isn't getting the juice it should one way or the other. I have read that many schools are 208V ut I'll have to wait til they open in Jan to check it out further.

I don't know if the teacher knows about this difference in voltages or not. she was already gone for Christmas break when I noticed it.

Thoughts? I doubt they will run a new service...being that we are unplugging/plugging in whichever kiln we need at the present time... but you sound very knowledgeable on all of this so I figured I'd take the liberty and ask what the dangers/trouble might be in continuing to run these kilns in such a manner.

also....Do the digital controllers adjust for this voltage difference and will the kiln still fire at the proper temp?

thanks for any insight

teardrop


Most schools have the 208v 3 phase service, but I have heard of at least one instance where they had what they were calling 480v split phase (I think). I don't know much about that.

You can run a 240v appliance on 208v service but the lower input power means fewer watts out, which in the case of ovens and kilns means they won't heat up as fast. So it'll run longer, but ultimately uses roughly the same amount of total power (less power x longer amt of time, should work out to about the same total power use for a complete cycle).

However the opposite isn't true. If you try to put a 208v appliance on 240v service, you will be putting MORE power through that thing than it is rated for, by about a third. Things will heat up faster. This sort of setup would be a fire hazard. It will cause excessive wear on the elements and will burn them out real quick, but that is the least of your worries. That excess power gets bled off in all directions as extra heat, and not just through the elements, but throughout the wiring of the kiln as well. Especially with a kiln, that already pumps out ungodly amounts of heat, this would be very dangerous. You'll also tend to get a lot of temperature fluctuations which can stress relays. Over all a very bad idea to run 208V appliances on 240v service. It's possible to do it by running it through a stepdown transformer (to reduce 240v to the 208v that would be safe for the kiln) but that seems kind of an expensive thing to do. My moneys on 208v service at your school, because I think you'd have had a fire by now or some other serious problems were it otherwise.

Also, there are a few kilns - I didn't note which ones, but a few - that will operate on either 208V or 240V service. I don't know if theres some user configuration involved with those or not, but they do make a few models that will operate on either service. So potentially one of those two kilns is a "switch hitter" and everybody really is still operating safely.

Constantly plugging/unplugging those kilns is going to stress those connectors in the plugs though, that's really not a good idea. If they're not inspecting those power cords regularly (and I'd be surprised if they were) that's another potential fire hazard. Appliances this big just aren't meant to be treated that way. If there's only one outlet maybe they should look into getting a switch installed, like I was talking about earlier. Depending on how many amps the "big" kiln is rated at, it might actually be cheaper to do the safe thing and wire in the extra outlet. Really shouldn't be repeatedly plugging/unplugging a kiln like that.

As for the controllers - I don't know much specifically about controllers for kilns, except that they are computers, and any computer just runs whatever program you load into it. If there are difference needed in the firing programs for the 208V or the 240V versions of a kiln that would be configured at the factory - it should be in the "firmware" and invisible to you as the end user. You have to trust the company that builds your kiln to get this right. If they couldn't handle it, you'd have heard about it by now, so no, there's nothing to worry about as far as the controllers go.

Hope that helps.

And don't go thinking I'm some sort of expert with all this. What I've been saying here is basically all surface stuff. I couldn't design the electrical system for an appliance to save my life, nor follow someone else's design. I just know where I should and shouldn't plug 'em in, and that only by checking the manual first, LOL!

#25 teardrop

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Posted 30 December 2011 - 11:17 AM

Thanks for the response.

there are obviously some problems that need to be worked out. I'm gonna >guess< and say that i think you are correct with the 208 volts guess for wiring at the college. I say this because the original kiln/the kiln owned by the school is the 208V 23" x 27"...and the larger 240V kiln is owned by the teacher and was brought in after the fact. I recently replaced the elements in both...though i don't know how many firings each underwent before the change/etc. (they are never fired to cone 10 because we have the gas kiln for that)

The plugs are both in shabby shape....I do know that for sure because I am tall and the ladies are all mostly short...and it's a contortion-type move to get yer arm back in the spot where the plug in is located. Being tall is also why I am targeted for unloading/loading the kiln. Many of the ladies can't even bend far enough or reach far enough to get to the bottom shelf (electric) or top shelves (gas). Therefore..very early-on in the class I was asked to help with the kilns. Fun stuff....mostly!

I'm gonna look into this a bit more once school starts back up next week. thanks for the insight.

teardrop


Be who you are and say what you feel, because those who mind don't matter and those who matter don't mind. Dr. Seuss US author & illustrator (1904 - 1991)

#26 bciskepottery

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Posted 30 December 2011 - 03:08 PM

Commercial installations are 208V; residential are 240V. That would likely explain why the school bought a 208V kiln and the instructor brought a 240V from home.

#27 Arnold Howard

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Posted 03 January 2012 - 03:04 PM

Kinda freaked me out when I saw that the smaller kiln is a 208 volt...the larger a 240 volt.... but get this...there's only one outlet..and obviously...it isn't BOTH voltages. I didn't take the cover off the electrical box to see what voltage it is..but needless to say...one of the kilns isn't getting the juice it should one way or the other. I have read that many schools are 208V ut I'll have to wait til they open in Jan to check it out further.

also....Do the digital controllers adjust for this voltage difference and will the kiln still fire at the proper temp?


Someone may have changed the elements in one of the kilns to match the voltage of the circuit. If you ever do that, have the kiln manufacturer send a new data plate showing the corrected voltage. That will aid you in ordering the correct elements for that kiln in the future.

Yes, digital controllers compensate for low or high voltage so the ware fires to the correct cone in Cone-Fire mode--provided the kiln has enough power to fire the ware.

Sincerely,

Arnold Howard
Paragon Industries, L.P., Mesquite, Texas USA
ahoward@paragonweb.com / www.paragonweb.com

#28 teardrop

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Posted 04 January 2012 - 10:28 AM

Someone may have changed the elements in one of the kilns to match the voltage of the circuit.


Thanks for this info, arnold...as well as the info on temp compensation via the digital controller.

I will have to investigate all of this further with my instructor. I was merely handed a box of new elements (twice) and asked to change them out. I didn't order them/etc. or look at the voltage rating to see if one or the other has been changed to match the voltage the outlet is putting out. It is possible that she is aware of all of this and it is old news. I will bring the topic up and see what she says.

Thanks for sharing your knowledge

teardrop
Be who you are and say what you feel, because those who mind don't matter and those who matter don't mind. Dr. Seuss US author & illustrator (1904 - 1991)




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