gas to electric conversion

[Maulik Oza]

hello everyone,

can anyone help me in converting my 20 cuft gas kiln into electirc kiln. i need to know how many elements will i need and how much electricity it will consume to reach cone 10.

[Norm Stuart]

Kanthal heating elements last about 100 firings at Cone 6.  Fired to Cone 10, the element life will be roughly 50 firings.

We have a 3.5 cu/ft kiln with 2.5 inch thick light firebrick and 36 amp which can easily reach Cone 10. 

A similar size kiln with 24 amp can reach Cone 10 when the heating elements are new, but takes about twice as long.

So 10 amps per cubic foot is good, but 6.86 amps per cubic foot is barely enough without more insulation.

The elements are divided up according to the maximum amperage rating of the power-relays.  The power relays cycle on then off to prevent the heating elements from getting too hot - hotter than they can dissipate their heat which makes their life less.

Jeff Poulter can probably tell you more.

[Maulik Oza]

hi norm,

thanks for reply.. kanthal A1 elements i can get easily. I have roughly 20 cuft kiln with 8 inches thick cerawool insulation ( 128 density, 1 inch thick and 1420 degree Celsius temp ). now to reach cone 10 will it take the same 10 amp per cubic foot ?

i will appreciate if jeff will also reply..:)

[Norm Stuart]

By the way, Maulik, the 36 amps uses 8.6 kWatts.  Starting with a $489 control box like the Bartlett V6-CF would be a place to start, but ask Jeff or a kiln designer if this can control the number of m/watts you have access to. 

http://www.clay-king.com/kilns/olympic_kilns/electro_sitter.html

We upgraded to a 220 Volt 50 amp outlet to handle the 36 amps - you always need 25% more than your design to prevent overheating in the outlet/building wires.

A lot will depend on how much wattage you will be able to gain access to.  In the US m/amps greater than 80 or 100 need direct connections without a plug, and much higher requires a three-phase AC which means the electric utility has to add a new transformer - which in the US costs the customer a lot.  You need more electrical design than I'm familiar with.

Marcia Selsor has designed electric and gas kilns around the world, and she may be interested in helping, perhaps for a fee.   http://www.marciaselsor.com/

Maulik Oza said:

hi norm,

thanks for reply.. kanthal A1 elements i can get easily. I have roughly 20 cuft kiln with 8 inches thick cerawool insulation ( 128 density, 1 inch thick and 1420 degree Celsius temp ). now to reach cone 10 will it take the same 10 amp per cubic foot ?

i will appreciate if jeff will also reply..:)

[George Lewter]

Element life is proportional to wire size. You can get extended life oversize elements such as Terry Fallon used in his reduction electric kilns that went to cone 11-12 with long holds and ramps for crystalline glazes. Euclids in Canada could help you with the engineering and produce them for you. I am temporarily in the same part of Florida as Terry Fallon, and have seen one of his kilns at MIY Ceramics, where I am working. Those are some beefy elements!  I understand that he is or has been quite ill and is not currently active in the business.

[Maulik Oza]

hi norm,

i understand what you are saying about requiring three phase AC line. we already have that because studio is located in industrial area. so that is not the problem. why i asked this question because i wanted to know approx cost of each firing so i can decide that should i go for electric or gas automatic kiln system. i know gas will be cheaper but there are other issues that we don't have gas pipe line connection so i will have to make manifold system with 6-10 cylinders. which is costing too much. 

thats why i just wanted to know how much difference it makes in firing with these two different fuel?

hi george,

i have seen the beefy elements which you are talking about.. in our school kiln it use to be there now its not working anymore. i am sure Terry Fallon can design it for me but then shipping and all those things will be too expensive for me so i will rather search it in to my locality and get it done.

thank you once again for reply....

you guys and this website have been very helpful..if you guys are visiting india anytime please please please visit my place.. i would like to meet you in person.

[Norm Stuart]

Even though Cone 10 is only 72 C hotter than Cone 6, it costs me about 1/3 more for this firing due to the environmental heat loss through our 2.5 inch fire brick.  You also have the more rapid replacement costs or heating elements and relays.

In my 3.5 cubic foot kiln, at $0.12 per kilowatt hour, these are my cost for electricity:

Cone 6   firing costs $5.90

Cone 9   firing costs $6.70

Cone 10 firing costs $7.90

In a larger kiln your surface area / volume will be less so your environmental heat loss will likely be a smaller percentage.

[Neil Estrick]

You can put as much power into it as you want, but you don't need 200 amps for a 20 cubic foot kiln. For example, an L&L TB3427-D DaVinci top load kiln, 21 cubic feet with high powered elements pulls 143 amps at 208V single phase, or 83 amps at 208V 3 phase (36548 watts). It's got almost 50% more power than the version with regular elements (24936 watts), although both are rated for cone 10. And those are made with only 3" brick. I think pulling any more power than that would be unnecessary. Remember that it's also going to depend on how much space is left in your breaker panel.

The bigger question is how are you going to install the elements? If the kiln is made of fiber, how will you attach the elements?

[Norm Stuart]

Euclid's Elements in Canada is a genius supplier.  They can supply the same $220 14 gauge elements we buy from our kiln manufacturer for $180 instead of $220, and they can supply thicker gauge 13 Gauge elements for our kiln for a mere $240.

Thanks George for a great new vendor!

George Lewter said:

Element life is proportional to wire size. You can get extended life oversize elements such as Terry Fallon used in his reduction electric kilns that went to cone 11-12 with long holds and ramps for crystalline glazes. Euclids in Canada could help you with the engineering and produce them for you. I am temporarily in the same part of Florida as Terry Fallon, and have seen one of his kilns at MIY Ceramics, where I am working. Those are some beefy elements!  I understand that he is or has been quite ill and is not currently active in the business.

[Jeff Poulter]

I think Euclids would be an excellent place to tell you how many elements you will need.  They have the formula for figuring it out posted on their website.  Thicker elements are better, but cost more.  Also, you may want to use SSR's as opposed to other relays.  They make the elements last longer.  Think of it as a dimmer, instead of switching a light off & on(It actually is switching much faster than a conventional relay, but it is feeding the element only what is required to heat at a certain rate).  jhp

[Norm Stuart]

Wouldn't the computer controller need to be reprogrammed to accommodate solid-state relays?

[Jeff Poulter]

No, it is supplying the needed power to heat the kiln, but is doing it at a constant rate, instead of on & off like regular relays.  jhp