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Kiln okay in a shed southern US?


KaiS
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Hi again
I'm in the research stage of wanting to get a kiln. The original owners of the house we recently moved to actually had a kiln in a large shed out in the yard. It would only take a simple update of wires to get everything up properly. Only I expect it to get extremely hot here in the summer in Florida. I can put fans, and leave the doors open for some good ventilation but I just want to be sure it'll be safe before I make the plans. It's strongly preferred to have the kiln at an outdoor location not attached to the house because of our parrot's sensitive lungs that can't be trusted even with a vent system, getting the kiln to be able to safely fire out in the shed in the summer is likely to be a strong deciding factor on if we'll be able to get a kiln or not. The shed isn't insulated (which I can do if need be) but it is moisture proof but I've heard about just how much kilns heat up a room and that the kiln reaching specific external temperatures is not safe. 

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The issue with kilns being unsafe at high temperatures relates to two factors. First, the kiln itself gives off significant radiant heat as it reaches final temperatures, so the physical space needs to be arranged in such a way that it will not catch fire. Specifically, that means minimum distances from any combustible surfaces and sufficient general ventilation that the accumulated heat does not induce damage.  Second, your hearing of the kiln itself not working at elevated temperatures is correct, but needs clarification as to exactly why. The electronic controllers have temperature sensors on the circuit board and are programmed to shut down when the temperature inside the controller goes below or above the allowable operating range. For extremely low temperatures, the issue is the thermocouple will give seemingly erratic readings and so the controller is programmed to refuse to start, but that is not likely for you. For extremely high temperatures (generally above 150F), the issue is that the circuits in the electronic semi-conductors become somewhat erratic and memory signals begin to jump their assigned channels and weird things (not always good) begin to happen, and so the controller will shut down in the middle of a firing. For that, you can arrange localized ventilation of the controller case by directing a small fan at it to blow room air (which might get warm, but not that hot) through its vent slots. In summary, you can do it with some care and planning.

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3 hours ago, KaiS said:

The shed isn't insulated (which I can do if need be) but it is moisture proof but I've heard about just how much kilns heat up a room and that the kiln reaching specific external temperatures is not safe. 

This is doable and makes me ask the following questions

  • What is the basic shed construction? (Metal, vinyl, wood)
  • What  is the shed floor construction?
  • What size is the kiln in KW, so you can have options on the exhaust

My sense is if the floor is reasonably non combustible and clearances are adequate I would design with a kiln hood such as that made by vent a kiln.   This may not remove all your heat but will remove most so controller issues and even just walking in midday would be tolerable. I would  also likely set this to run automatically on a thermostat and would also incorporate that in my electrical requirements before running new wires. For kilns we always suggest limiting the voltage drop to 1% or less to maximize how many firings you can get on a set of elements rather than the electricians typical 3% convention.

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  • 4 weeks later...
On 2/24/2021 at 2:41 AM, Bill Kielb said:

This is doable and makes me ask the following questions

  • What is the basic shed construction? (Metal, vinyl, wood)
  • What  is the shed floor construction?
  • What size is the kiln in KW, so you can have options on the exhaust

My sense is if the floor is reasonably non combustible and clearances are adequate I would design with a kiln hood such as that made by vent a kiln.   This may not remove all your heat but will remove most so controller issues and even just walking in midday would be tolerable. I would  also likely set this to run automatically on a thermostat and would also incorporate that in my electrical requirements before running new wires. For kilns we always suggest limiting the voltage drop to 1% or less to maximize how many firings you can get on a set of elements rather than the electricians typical 3% convention.

The shed is wood, OSB ply. It's 15-20 years old in fair condition. No major issues, it mostly just shows age. It's 14x10 footprint. And the peak of the roof is 10 feet. It already has some built in ventilation, but I can easily add more. The floor is also plywood, but I've seen mentioned in other posts that if I can get it on a nice solid floor of a layer or two of stone or cement pavers I may be able to work around the floor issue. 

I do not need to be able to use the shed as a studio, it will largely still just be used for storage and I will do any of my working in the house, but of course the shed can't reach dangerous levels for the kiln or wood structure but so long as it doesn't reach dangerous temperatures, it doesn't matter if it's too uncomfortably warm to work in as we'd only be in and out for dropping off projects. 

I'm still in the research stage, but one of the kilns that was the top of the list was an Olympic 1818HE. I'm still not an expert on the electrical side of things but this is the information from the listing. There's a breaker box in the shed, it's just not connected to the house anymore, the wires were cut when the house was last sold. The breakers in the house that seem to lead to the shed is a 60amp. 

Voltage 240
Watts 5,040
Amps 21

 


So sorry it's so long since you referenced this post last, I'm known to be incredibly impulsive so I've been actively trying to slow myself down when it comes to such a costly decision 

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@KaiS Your kiln will need a 30 amp breaker. If you've got 60 amps going to the shed, put in a 60 amp sub-panel, then run the 30 amp line for the kiln off of that. That'll leave you enough to run a circuit for lights or venting, too. Put two layers of cement board under the kiln, extending at least a foot beyond the kiln. You could also put some on the walls near the kiln if you want. My kids' school paneled one entire end of their kiln shed with cement board. If the kiln is digital, you want good venting to keep the controller happy and extend the life of the elements. For venting, you could do something as simple as using an inexpensive 6" inline duct fan to pull out heat. Cut a 6" hole in the wall, install a cap and duct (like a clothes dryer vent), and connect to the fan with a flexible duct. If you've already got other vent openings you wouldn't need to make any other holes for makeup air.

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5 minutes ago, neilestrick said:

@KaiS Your kiln will need a 30 amp breaker. If you've got 60 amps going to the shed, put in a 60 amp sub-panel, then run the 30 amp line for the kiln off of that. That'll leave you enough to run a circuit for lights or venting, too. Put two layers of cement board under the kiln, extending at least a foot beyond the kiln. You could also put some on the walls near the kiln if you want. My kids' school paneled one entire end of their kiln shed with cement board. If the kiln is digital, you want good venting to keep the controller happy and extend the life of the elements. For venting, you could do something as simple as using an inexpensive 6" inline duct fan to pull out heat. Cut a 6" hole in the wall, install a cap and duct (like a clothes dryer vent), and connect to the fan with a flexible duct. If you've already got other vent openings you wouldn't need to make any other holes for makeup air.

Thanks! Making a whole corner where the kiln would go sounds like an easy way for peace of mind against the heat and wood. And I planned something exactly like you'd mentioned, just sticking a fan in one wall, and with the other passive vents it should create a nice flow through there.  There's already two 30 amp breakers in there, and wiring for some outlets, and a shop light, such a shame they went and cut the power to the shed but hopefully it shouldn't take too much to get everything connected once more. Thanks so much for the advice, hopefully I'll be back to the forum some time soon with good news haha 

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kai, one other suggestion is to raise the cement board  putting it on a brick or some other thing on the floor.    on the wall sections  install  it away from the actual wall, made of wood, by at least an inch.   spacers used between the wood and the cement  board are really simple a couple  of thick steel nuts over the screws that hold the cement board to the wall.  that leaves an air space between the cement board and the wood and will keep the wood from getting too warm.   warmth over time equals more flammability than you want in the wood wall.

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Hi Kai,

I have an outdoor kiln here in Tucson Arizona. It is a large 50 amp model. No ventilation. I have it sitting about a foot and a half away from the side of my house which is wood (shiplap). The wall temp at that distance gets to about 110 degrees F but nothing worse than our usual desert summers. So the walls are okay... However, the heat that comes off the unit going up is quite significant if trapped by the ceiling. You will definitely need ventilation in the shed, and make sure you do one of those upper vents like the rotating vent that looks like a chef hat!  If you want to keep yours outdoors, I protect it when not in use with a BBQ cover.

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An issue with sectional kilns is the sections and lid typically do not have totally sealed joints so there is some heat loss through the cracks. It is considered normal, you can't do much to stop it from happening and it usually isn't a problem for firing the kiln. However, if the kiln is close to a flammable wall, the little red stripe  of "reverse-shadow" from the radiant heat near the end of the firing will be much hotter than the rest of the general surface, and that will be where the fire starts. Protect the whole wall behind the kiln with a layer of cement board. And even better, as oldlady notes above, install it with an air gap to further insulate the flammable material behind it. For this, it is best to leave a few inches open at the bottom and top so that a convection air current will naturally occur to carry the warmth up and out.

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With 16 inches clearance from any walls you'll be safe. Cement board wouldn't hurt, though.

5 hours ago, Stumonster Clayworks said:

 If you want to keep yours outdoors, I protect it when not in use with a BBQ cover.

The problem with leaving a kiln exposed when in use and just covering it when idle is that the weather can change very quickly in many parts of the country. You have to be able to keep it open for the entire firing process, heating and cooling, which can be anywhere from 24 to 48 hours or more depending on the size of the kiln. In Arizona that's probably not a problem. In the Midwest (and other areas) it's a huge risk, as weather predictions are far from accurate and storms move in without any notice. Having to work around the weather also means not being able to fire the kiln whenever you want to, and possibly missing deadlines. I've also seen kilns corrode really quickly when covered with tarps. Again, probably not an issue in Arizona, but anywhere with humidity and that moisture gets trapped under the tarp and eats away at the kiln. And don't forget about spiders, snakes, and other critters that like a dark, quiet space. For manual kilns you can get away with a little more abuse, but my rule of thumb for digital kilns is: if you're not wiling to leave your laptop there, then you shouldn't leave your kiln there.

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On 3/20/2021 at 7:41 PM, oldlady said:

kai, one other suggestion is to raise the cement board  putting it on a brick or some other thing on the floor.    on the wall sections  install  it away from the actual wall, made of wood, by at least an inch.   spacers used between the wood and the cement  board are really simple a couple  of thick steel nuts over the screws that hold the cement board to the wall.  that leaves an air space between the cement board and the wood and will keep the wood from getting too warm.   warmth over time equals more flammability than you want in the wood wall.

The interior of the shed isn't insulated, it's just the 2x4s and outer sheathing, so there'd be 3.5 inches of air between the wooden exterior wall, and the cement board. I definitely plan to put spacers for the floor as well thank you for the reminders!

 

 

On 3/21/2021 at 1:40 PM, Stumonster Clayworks said:

Hi Kai,

I have an outdoor kiln here in Tucson Arizona. It is a large 50 amp model. No ventilation. I have it sitting about a foot and a half away from the side of my house which is wood (shiplap). The wall temp at that distance gets to about 110 degrees F but nothing worse than our usual desert summers. So the walls are okay... However, the heat that comes off the unit going up is quite significant if trapped by the ceiling. You will definitely need ventilation in the shed, and make sure you do one of those upper vents like the rotating vent that looks like a chef hat!  If you want to keep yours outdoors, I protect it when not in use with a BBQ cover.

Thank you, I've got to get in the shed and really take a good look. The roof is actually shingled just like a house would be, and there's a couple vents up high and a strange strip down the middle that I've yet to figure out. I'll definitely be adding in several powered fans, maybe one low one high, I'm looking to achieve a sort of cross breeze to draw air out of the shed.  This area gets too much rain, and humidity to put it just outside even if it is under the roof, but the shed shows no signs of water damage thankfully so it should be safe there. 

 

 

22 hours ago, neilestrick said:

With 16 inches clearance from any walls you'll be safe. Cement board wouldn't hurt, though.

The problem with leaving a kiln exposed when in use and just covering it when idle is that the weather can change very quickly in many parts of the country. You have to be able to keep it open for the entire firing process, heating and cooling, which can be anywhere from 24 to 48 hours or more depending on the size of the kiln. In Arizona that's probably not a problem. In the Midwest (and other areas) it's a huge risk, as weather predictions are far from accurate and storms move in without any notice. Having to work around the weather also means not being able to fire the kiln whenever you want to, and possibly missing deadlines. I've also seen kilns corrode really quickly when covered with tarps. Again, probably not an issue in Arizona, but anywhere with humidity and that moisture gets trapped under the tarp and eats away at the kiln. And don't forget about spiders, snakes, and other critters that like a dark, quiet space. For manual kilns you can get away with a little more abuse, but my rule of thumb for digital kilns is: if you're not wiling to leave your laptop there, then you shouldn't leave your kiln there.

I'll add the board for peace of mind since the shed's not exactly brand new, and I'll be able to give it as much clearance as I want, I'll probably give it a nice solid bubble around it to keep it from walls and things. 

And not to worry, the weather here with the rains, and humidity I'll be keeping it in the shed. Even though the shed is still bound to get more humid than an indoor temperature controlled room it's better than nothing. It at least doesn't seem to get wet from rains or anything like that. 

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