Shed spontaneously combusting

[Mark C.]

Kiln to close to combustibles just like a water heater to close to combustables = fire

Ok its a human thing

[Callie Beller Diesel]

I’d place good odds on that kiln being a gas fired one meant for metallurgy, not an electric pottery kiln. The ones for knives etc are small and relatively easy to make with a few things from a welder’s supply, but depending on the maker they also can be haphazard affairs. 

[davidh4976]

Another data point.  We fired our Paragon Viking 28 yesterday to cone 6.  It's a 60 amp kiln and has a 29" deep by 28" wide chamber. It is 12" from a wall which is consistent with the Paragon manual's requirements. The hottest point on the wall was 160F; still below the 170F cited in the article for combustion with long term heat exposure.  Kiln sides 280F, top 380F.  It's in a warehouse type facility with ceilings that are way too high to get a temperature reading on them.

[Mark C.]

2 hours ago, davidh4976 said:

Another data point.  We fired our Paragon Viking 28 yesterday to cone 6.  It's a 60 amp kiln and has a 29" deep by 28" wide chamber. It is 12" from a wall which is consistent with the Paragon manual's requirements. The hottest point on the wall was 160F; still below the 170F cited in the article for combustion with long term heat exposure.  Kiln sides 280F, top 380F.  It's in a warehouse type facility with ceilings that are way too high to get a temperature reading on them.

A bit of cement board held off wall  a bit would help any kiln situation to keep walls cooler

[Bill Kielb]

On 9/10/2024 at 12:01 PM, davidh4976 said:

It is 12" from a wall which is consistent with the Paragon manual's requirements. The hottest point on the wall was 160F

Wow, warehouse volume of cooling and made it to 160? Too close for me actually. I have to assume natural cooling so fairly dependent on outdoor air temperature. I think this is the common sense part and seems too close for my comfort. Fail safe ventilation would be something I would definitely add to make sure a minor change in outdoor temp or someone accidentally leaving a door closed doesn’t let this increase. Guidance on distance from paragon is reasonable but I believe all the major brands have guidance on accounting for HVAC (cooling / ventilation) now in their setting up a kiln room docs.

Just looking at old L&L docs bases on 2000 mech code, looks like they were citing less than 160 degrees.

Edited September 13 by Bill Kielb

[davidh4976]

25 minutes ago, Bill Kielb said:

Wow, warehouse volume of cooling and made it to 160? Too close for me actually. I have to assume natural cooling so fairly dependent on outdoor air temperature.

The wall temperature is more due to radiant heat than air movement.  In any event, although Paragon says 12 inches, I'm also thinking that 160F is a bit too high and I plan move the kiln further out from the wall.  Of the five kilns I use/maintain, it is the only one that doesn't have at least 18 inches of separation from a wall.

Thanks for the reference to the Uniform Mechanical Code! I found the 2024 version online (https://epubs.iapmo.org/2024/UMC/. It has some interesting tables on how one can reduce the clearance from a wall depending upon the wall's construction. For instance, if 18 inches is required, if you use two layers of galvanized sheet metal, with one inch of airspace between the metal sheets and one inch of airspace between the sheets and the combustible wall, you can reduce that to 6 inches (assuming all the layers are held apart by non-combustible material such as metal pipe).  Very interesting (at least it is to me!).

The 2024 version states an exception to it's specified clearances, saying that kiln clearances can be reduced to what the manufacturer specifies as part of their UL listing. I assume that to get UL approval, the kiln manufacturers have tested to find the minimum clearances for their products that keep the wall at or below 160F. That is consistent with my testing that showed at Paragon's minimum of 12 inches, the wall was exactly 160F at its hottest point. 

 

[Bill Kielb]

3 hours ago, davidh4976 said:

you can reduce that to 6 inches (assuming all the layers are held apart by non-combustible material such as metal pipe).  Very interesting (at least it is to me!).

There are always qualifiers. An air gap can help because it allows cooling. If there is no cooling then everything is going to warm. The example of the restaurant fire starting because of the bolted penetrations was a new find at the time. 

Manufactures will always defer to local codes. NFPA often will take precedence or be cited in mechanical codes, there will always be qualifiers so a distance measurement is always dependent on local cooling. Again, real fire proof construction as in metal studs, layers of drywall - proven conservative methods ….. nothing to burn. 

Cooling is always an important part of the equation and most methods rely on being cooled by the ambient air temp ……. Except for non combustible construction practices. Everyone will attempt to defer to the manufacturers and manufacturers will defer to local code and local codes are often adopted years after publication. 

Most locations may be using 2020 mechanical codes yet. It’s not really fair for manufactures to be 100% accountable for some random kiln enclosure. The UL test and certified spacing assumes the interior space will not be greater than 100. It’s my suggestion to be conservative and cautious. If there is a minimum distance it’s likely qualified by ambient air temp.  Be safe, don’t try and design your own, if you do though then I suggest diligent common sense should be exercised. Measuring the actual temperature is a very proactive and an impressive double check on your part IMO.  Now likely time to improve the setup a bit.

Edited September 13 by Bill Kielb

[neilestrick]

On 9/4/2024 at 8:31 PM, Bill Kielb said:

More interesting 99 degree ambient and surface temperatures in the 128 - 137 range, I mention this because the typical control board safety is 100 degrees and you measured 99 degrees ambient which is very close to the board safety temperature.

Most kiln control board safeties are set to 140-160 F. At 100F we'd see error codes all the time. The Genesis can operate at temps up to 180F.

[Willow Wood Pottery]

I'm just starting out and want to build a pottery studio for myself.  Reading this thread has really got me thinking about where the kiln should go.  I have two options - a concrete block garage with a cement floor and wood frame roof that is attached to the house, or a 10x12' wood frame shed with wooden floor and a 60-amp subpanel that is approximately 25' away from the house.  My kiln is an older L&L rated at right around 30 amps.  I do have a downdraft vent for the kiln for fumes, but nothing in place yet for extracting heat from the space.  I'm wondering what the best option is.  Away from the main house seems safer, although a lot of wall and floor prep would have to be done to make the shed safe.  Although I would like to have everything in one place, I'm not opposed to having the kiln in one area and the rest of the studio in another.  Any advice would be most appreciated.

[Bill Kielb]

8 hours ago, Willow Wood Pottery said:

I'm not opposed to having the kiln in one area and the rest of the studio in another.  Any advice would be most appreciated.

I would definitely have the kiln separate from the work area if possible. While fire proofing is a thing, you may have surmised if you read the thread above that cooling is an important component to the how far should I place my kiln from a combustible wall. So just placing it somewhere at a distance is one component. You are in Florida so your average outdoor air temps are going to be higher than many in Northern latitudes. I think I would pick the shed and add a through wall cooling fan and and fixed inlet louver to remove most of the heat. Fireproof under around and over the kiln reasonably and it may sound funny but just supervise from time to time to make sure it is operating as expected. I think if you read the thread @davidh4976 realizes now that firing in the garage probably will exceed the controller limit if warmer than approximately 85 degrees outdoors and firing in the warehouse is beyond the wall temp he probably wants. In both cases this was discovered by checking temperature rather than assuming spacing was the key. Removing the heat is important as well. @davidh4976 may increase the size of his cooling fan in his garage, add ventilation to the warehouse or only fire when cooler outdoors. Being proactive and checking on things IMO a common sense thing that always should be done.

The shed is separate from the house so no issue with kiln fumes in the house, my thought would be the shed with reasonable fire protection under, above and around the kiln (3 feet all directions I believe is suggested) and an exhaust fan sized to remove most of the heat. So to limit the heat to 115 degrees indoors on a 95 degree outdoor day, your fan would be about 1200 cfm. Just a quick approximation though, assumes you are removing ALL 30 amps theoretical so probably conservative as the kiln may not run continuously at 30 amps (30x240v = 7200 w, 7200 x 3.41=  24552 btuh) and it instantly will not leave the kiln but is spread out over time meaning a smaller fan will be able to keep up.

Very doable if planned for I believe. I have been using some economical variable speed fans with great success (Ac Infinity), so most of the time when cooler outdoors the fan will slow down to maintain a set temperature - let’s say 80 degree setpoint before it goes full speed.

L&L has decent ( updated) guidance IMO here for cooling https://hotkilns.com/support/pottery-kiln-knowledgebase/calculating-ventilation-requirements-heat-kiln-room. There support section I believe is very practical here: https://hotkilns.com/support/installation. You should do your own planning to be sure of the numbers.

Others here may have suggestions as well, this is just my experience.

Example shutter fan below I have had success with and can be monitored or controlled on your phone so you can add alarms I believe as well.

Edited Sunday at 07:31 AM by Bill Kielb

[Willow Wood Pottery]

Thank you @Bill Kielb, that is great advice.  I forgot to mention that there are two windows on opposite sides of the shed that I can also open to allow fresh air in when firing the kiln.  I will definitely look into the AC Infinity exhaust fan.  I have a wall mounted Skutt kiln controller that I will be using and have been concerned with keeping it cool enough.  Hopefully with the exhaust fan mounted up near the roof peak (the shed has a barn-style roof) and the two windows open a bit, it will be enough to keep things from getting too hot.  Thank you for the L&L links as well, I will read up on that for sure.

[Bill Kielb]

2 hours ago, Willow Wood Pottery said:

Hopefully with the exhaust fan mounted up near the roof peak (the shed has a barn-style roof) and the two windows open a bit,

Yes, if you size the exhaust adequately then you should be able to maintain ambient outdoor temp. Window definitely can take the place of fixed inlet. Fan in window to start gets you an idea if you need a larger exhaust fan. I like permanent wall exhaust and inlet air louver if possible because it is always capable rain or shine and they usually come with built in bug screen. Permanent exhaust on a thermostat can also help ensure the oops,  I forgot to open the windows enough ……. And can provide an alarm if things get too warm. Gable end mounting is fine, if you can find a suitable low wall mount for the inlet (not in sun) that would be best. Florida, Sun can add a bunch so light colors where practical. With some diligence you should be able to solve all reasonably.

Edited Sunday at 02:12 PM by Bill Kielb

[Hulk]

"...a pottery studio for myself.  Reading this thread has really got me thinking about where the kiln should go..."

My first setup, kiln in the Studio (a one car garage with high ceiling and a big side window) - there wasn't anywhere else practical to put it.

Second/current setup, kiln on a covered patio.

There's +/- either way, imo.
My impression is most potters would prefer to have the kiln close by, where the carrying back and forth is much less; that may be the main thing there.
On the other end, the heat, fumes and noise* are removed, entirely, and the space is freed up as well.

I prefer having the kiln out of the Studio.
 

*effective heat control and fume removal will very likely involve fan noise, a lot of fan noise.
Downdraft powered kiln vent made a big difference in fumes, my experience, but did not get all the fumes ...and, loud.
For heat, we made up a dyi overhead hood to six inch duct, powered by a 400 cfm fan, focused on the problem - heat and fumes at the kiln - effective, loud.

The fan and ducting have been repurposed as dust control for the glaze mixing station.

[Willow Wood Pottery]

21 hours ago, Hulk said:

My impression is most potters would prefer to have the kiln close by, where the carrying back and forth is much less; that may be the main thing there.

This is definitely a concern for me.  I would have to carry ware from the garage, through a side door and through a set of wooden gates, and across the yard to the shed for firing.  And back again.  In the Florida heat/rain.  (And I have been known to be a bit clumsy.  lol)

My other thought was to partition off the end of my 10x20' one-car garage for a kiln room, where the overhead door is.  The main electrical panel is there.  Also, the garage ceiling currently is just open rafters up to the attic space above. With the downdraft kiln vent I have and a powered extraction fan as @Bill Kielb suggested, I would think fumes and heat should be drawn out of the space.  I could raise the garage door a couple of inches when firing to allow fresh air to enter.

The remaining portion of the garage could be drywalled, insulated, and air conditioned for my studio work area.  The kiln room would end up being approximately 10x7', with the rest around 10x12', minus the existing washer, dryer and water heater, so in the end, maybe 10x8' of usable space.

I'm really not sure which would be the better way to go.

 

[Bill Kielb]

2 hours ago, Willow Wood Pottery said:

powered extraction fan as @Bill Kielb suggested, I would think fumes and heat should be drawn out of the space.  I could raise the garage door a couple of inches when firing to allow fresh air to enter.

Can be done, I highly suggest (if by exhaust)  you will need to size a large enough fan that can remove all the heat as practical, especially for a small space. Maybe apply the L&L cooling equation with 100 degree max indoor temp and 95 degree outdoor temp. I would probably look to exhaust this through the roof to keep the noise from the neighbors reasonable. I would cut in an inlet air louver that is barometric so your fan always keeps this room ever so slightly negative preventing fumes from migrating into your work area and the house. 

So I would suggest pick your kiln from the L&L table here: https://hotkilns.com/hk-pdfs/%3Asites%3Adefault%3Afiles%3Apdf%3ABTUS-Easy-Fire or equivalent table and size as shown here: https://hotkilns.com/support/pottery-kiln-knowledgebase/calculating-ventilation-requirements-heat-kiln-room

So an example would be prox. 14267 btu for an e23- 2-1/2” brick (yours may differ and be much lower). 14267/(1.08x(100-95)) ~ 2642 CFM to remove the heat so the room remains 100 degrees or less when it’s 95 outdoors and the kiln is running top temp. If we limit our runs where the outdoor air is 85 at end of run prox. - 1321 Cfm. ……For 75 degree outdoor air limitation,  prox 528 cfm.

As you can see actual kiln losses very important, 500 - 600 cfm is pretty doable for cooler outdoor air temps and use of ductwork at these CFM  in the 6-8” round sizing acceptable for airflow and noise.

Just to add, if you wanted to do this with air conditioning (mechanical cooling) just for the sensible load (no humidity) the fan could be sized smaller to capture just the fumes and the AC could be sized to offset the kiln load, prox  14267 btu (Slightly over 1 ton) for the example kiln, but also would need to include the latent load likely 400 cfm of outdoor air for the hood and fume extraction. …..at some design outdoor humidity. Anyway the latent component is likely giant with your typical local humidity so without checking 3 tons mechanical  is a SWAG.

It does become more complicated but doable. I would suggest careful planning for sure trying to create a lasting safe space that is efficient as practical. You will be paying kiln electric to heat and potential significant additional electric to remove the heat mechanically or through exhaust.

I suggest a decent HVAC plan and outside review if done by a local HVAC service company. Kiln loads not necessarily something most deal with.

Just an aside - I don’t like interior temperatures to grow beyond human limits. At 120 degree indoor temp folks don’t last too long, so my design preference would be to make sure this can’t happen. Your prox 100 degree controller limit is a good thing IMO in this case. Also if your breaker box is in this room, the circuit breakers could likely be heated beyond design just from ambient temps. Keeping the panel in the kiln room not necessarily a good thing.

Edited Monday at 03:49 PM by Bill Kielb