# question about heating element in kiln



## ericrm (Jan 11, 2013)

i have dismentle the biggest of the 2 kiln and i wanna use the parts to build project on 110v. 

can someone help me figure out about the basic of electricity and how the heating element work?
i want to put it on 110v, i have acces to 11 or 12 amp

is it the voltage that create the heat or the amp?
how do i calculate the max lenth of element that i could use.

also i would guess that the brick are a form of insulation right?


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## jimdoc (Jan 11, 2013)

I have one like that, and I plan on setting it up for propane. I already removed the elements and controls. I don't think electric is the way to go for our purposes.

Jim

http://www.youtube.com/results?search_query=propane+kiln&oq=propane+kil&gs_l=youtube.1.0.0.1466.5209.0.7071.11.11.0.0.0.0.161.1426.0j11.11.0...0.0...1ac.1.0Y01PxekDRE


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## ericrm (Jan 11, 2013)

i know what you mean ,element are easyly corode and the brick is very easy to destroy with molten slag or spill, i learned that here  
those kiln can do it but because theyr werent made for that it come with too much problem...


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## Jimmy (Jan 11, 2013)

That refractory is only good for a oxidizing or neutral atsmophere. Propane would eat it up. You can try some refractory coatings but they are not cheap.
Let me know what model kiln it is and Ill see what I can do on the elements.
I need to know the type (material) of element and the diameter.
But. If you are looking to melt metals other than perhaps aluminum, 110v and 12 amps aint gonna do it.


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## ericrm (Jan 11, 2013)

im not that good with a vernier but i would guess that the size of the wire is around 54/1000 of an inch.
and from what i have read probably nichrome as it is nothing special and the kiln is rated at 2350f

i dont intent to put the kiln on 110v ,i mean that on the other use for the wire it will be 110v


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## ericrm (Jan 11, 2013)

ok my little light go on and i had a good idea... looked at the watts on the kiln 10350 and counted how much wire theyr was... so the expected watts for each wire should be at 862.5 watts wire
that bring me at 862.5 / 220v = 3.9 amp by wire at 220 v

how do i transfer it to 110v?

i have read on a post not here that i have to divide watts by 4 since i put it on 110v and do the same calculation

(862.5 watts / 4 ) / 110v = 1.96 amp by wire 

am i correct with that?

edit : also how does the lenth of the wire change the equation ? i would think shorter wire mean less watts,witch mean so less amps consumption?
but will my element glow as red as with the 220 on the 110 since they is less amp passing tru?


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## Jimmy (Jan 11, 2013)

Really need to know how they wired the kiln. The elements can already be 120v or they may need to be installed in series.

Here is a hand book that will help you alot.

Kilns of that type usually use A-1 wire.

http://www2.kanthal.com/sandvik/0971/internet/s003237.nsf/F6421C7808255963C12572BB001C8704/$file/1-A-2-3%20appliance%20handbook%20US.pdf


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## ericrm (Jan 11, 2013)

i had 4 control on the kiln, each one on 3 wire in series (one connected, one the other 3 time to make 1 long wire)


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## ericrm (Jan 11, 2013)

damn an other brilliant idea . i did an ohm check on 3 wire :idea: 10.4

so if im correct (not from me but the internet) The formula is: current squared divided by resistance equals watts
220x220/ 10.4 = 4653 watt
(110v x 110v)/ 10.4 = 1163 watt

when i do the math on the wire i come to 55836 watts when working on the 220v.but the kiln is rated 10350 watts. is it always like that, and theyr volontary refrain the comsumption? ,or do i messed up something in my calculation/technic

so if i dint made mistake, 1163 watts / 110v = 10.57amp . so 1 wire should be my limit at 110 v to be in the 11amp range ?

edit ohm check on 3 *different* wire and get 10.4 each


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## butcher (Jan 11, 2013)

Something seems wrong.
it is hard to tell without looking at it.

What does the name plate say.

Are the heaters wired in series or parallel, for single phase or three phase, are they all good, did you measure individual heater element, or did you measure them wired in series or parallel?


Say the name plate says 10350 watt, assuming 220 volt single phase:
P/E=I
10350 watts / 220volts = 47 amps

Then calculating resistance of the heater
E/I=R
220v / 47A = 4.6 Ohm 

Usually (but not always much depends on the equipment) heaters will be wired in series for low voltage, and parallel for high voltage.

Three heater elements can be wired single or three phase.

I would have to know more about what you have, individual heater resistance and how they are wired, to really determine anything.


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## ericrm (Jan 11, 2013)

d..m that thing is compliquated 

the plate say 10350watts 220v i dont remember the rest

the unplugged individual element ohm is 10.4 (tested by me, i could have made a mistake but i have tested 2 element and they both gave 10.4)
theyr work with 4 round gradator like those on old electric stove
i think the 4 gradator are connected in paralel 
but each gradator is connected to the 3 element, in serie (one end make the other beginning)

i cannot answer about phase,i dont know what is is...


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## butcher (Jan 11, 2013)

What is 4 gradator.

Formula for calculating more than two resistors in parallel:
R total = 1 / (1/R1 + 1/R2 + 1/R3)

So for three 10.4 ohms resistors or heaters, wired in parallel the total resistance is about 3.46 ohms.

So 

220 Volts / 3.46 Ohms = 63.5 amps

220 Volts X 63.5 Amps = 13,970 watts


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## ericrm (Jan 12, 2013)

a few pic will help i hope


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## ericrm (Jan 12, 2013)

i have tryed again to calculate ...

10.4ohm x 3 resistor = 31.2 ohm
than
R total = 1 / (1/R1 + 1/R2 + 1/R3+1/R4)
R= 1/ (1/31.2+1/31.2+1/31.2+1/31.2)
R = 1/0.128
R in paralel= 7.8

220v/7.8ohm = 28.2 amp

................................................................................... i feel like in scool ,my head hurt and the result arent as easy as i would love :roll:


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## butcher (Jan 12, 2013)

ericrm, 

I have not read the math in the last post yet; I will look at it later.

There are several combinations these elements can be wired, and they could be wired for several different voltages, single or three phase using Delta or Wye, we could rewire the kiln several different ways using the same elements, they can even be wired to use both 120 volt and 240 volt depending on heat setting or switches.

On 240 volt we could be running the elements on 120 volt, or on 240 volt using single element, or parallel elements, or a combination of series and parallel elements, we could also do this on one kiln to get different temperatures through switching.

I done quite a bit of thinking and came up with some math for a three element kiln using 10.4 ohm elements, using 120 and 240 volt switching and in a series parallel circuit, one top element @120volt, and two bottom elements in parallel (the two elements 10.4 Ohm in parallel give 5.2 ohms) at 120 volt, {and all three elements (series-parallel) give 15.6 Ohms} at 240 volt. to get different heat setting on the kiln, (this is often used in pottery kilns).

But now that I see your picture, it looks like I wasted my time.

Right now we need more information before we can worry about ohms law and calculations, we first must know how it is wired.

It would be helpful if we had a company brand name, model number, wattage, and voltage.

It is hard to tell but the picture looks like there are four switches, and possibly four elements.

We need to draw schematic, or find one on line for your kiln.

Do not get a Headache.

This is easy, the only trouble is you and you kiln are there, and I am here; if we were all together we could do it fairly quick.

But this will help you once you see what is going on, and you can learn a lot from it.

Can you draw it up in some kind of picture on a picture program, or on paper and scan it when done?

Do you have brand and model or name plate data volts, amps wattage, even if you do not we can figure it out, how many elements, how many switches, what type of plug (how many prongs, what do the prongs look like, these are also clues.


Draw the elements and switches on paper, and then draw in wires and connections to make a schematic.

(If you have model and brand see if you can find schematic online, and follow it, or one like yours).

It may be helpful to number switches, and elements connections on your kiln (use a marker) use the numbers (or letters), on your schematic to indicate connections, (this will help from getting confused), if switches already have numbers or letters use them in your drawing.

An ohmmeter is helpful in finding were the other end of an element of connection goes.

Sometimes it may be helpful to unwire a connection and trace it with the meter.

Trace the wire from the plug start with one prong draw wire (if connection put a dot) if more than one wire to the connection show other wire coming from the dot, (but only trace or follow one wire for now (to make your drawing), if it goes to a switch draw the switch (these look like infinity switches used on heating appliances you can get information on them with Google), draw where wire goes from switch to heater element connection (dot), (if more than one heater element wire from inside furnace, show this coming from the dot trace the heater wire in and back out of the heater (draw coil of wire or resistor for that element) back to dot (or other connection out side of kiln) and possibly back to the switch and then back to the other prong on the electrical plug.

You will have to do this for all elements and switches; you will find sometimes wires come back to a dot you already drawn and numbered.

The better you can label or name devices or connections on both the kiln and on you paper the less confused you will get if wires is colored note it.

It can be a bit confusing at first if your not used to doing this, but you can do it.
Try to make your drawing as neat as possible, and you may have to redraw it once it is all on paper to make it easier to read and make sense.

Then you can find schematics of kiln online (hopefully yours from your model number or brand), if not one similar, or if you can scan it and post it I can help, from this schematic and Ohm reading of a single element we can figure it out using Ohms law.

I hope this will be helpful, I have to get some sleep.


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## ericrm (Jan 12, 2013)

ill do my best
thanks for your time butcher


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## butcher (Jan 12, 2013)

You can have many combinations of how elements are wired four elements could be wired (two in series on one switch) and (two in series on another switch) and these sets of elements in parallel if both are switched on, there are just so many different ways they can wire these kilns.

paragon wiring diagrams:

http://www.paragonweb.com/Wiring_Diagrams.cfm

Look through these for ideas who knows you may find one wired just like yours.

infniite switch:
http://en.wikipedia.org/wiki/Infinite_switch
http://appliancejunk.com/blog/2010/...range-burner-infinite-element-control-switch/


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## ericrm (Jan 13, 2013)

this should be it



can i use a 240v infinite switch on 110v , and witch what result?

edit i have change the picture i had made a mistake on one of the switch


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## Jimmy (Jan 13, 2013)

Strech out a piece of element about a foot and measure the resistance. This will help alot. They we can figure out what wire you have and how long they are.


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## butcher (Jan 13, 2013)

I have to say that is one of the best schematics I have seen, great job.

I still have a couple of questions, is the 10.4 ohm for all three heating coils on each switch, or for each individual coil?

I will assume each coil and three elements to a switch and work the math from there.

The infinite switch works with current going through the switch and heater, the current heat a bi metal strip that will open the switch and close the switch to maintain heater temperature, you could use the 240 volt switch on 110 volt but the current would be so different it would not work the same, it would be better to get 110 volt infinite switches.


Why would you want to convert the furnace to 11O volt, it would be better to leave it 240 volt.

The green wire is it just earth ground? that is what it looks to me at this point, is it connected to the metal parts of the furnace.
As best as I can tell this is strictly 240 volt with no neutral wire.

The three coils element heaters if read 10.4 Ohms each this in series gives 31.2 ohms for each heater (3 coils) on each switch.
series resistors add.
E/R=I
240Volt / 31.2 Ohm = 7.69 Amps
ExI=P
240 volt X 7.69 A = 1845.6 watts

Note: this is if just one heater was turned on.

now what we have is four of these 31.2 Ohm heaters (3 x 10.4) switched in a parallel circuit.

(I will not do the math for if two or three heaters are on although we could).

With all four 31.2 heaters in the parallel circuit the circuit sees 7.8 Ohms total.

240 Volt / 7.8 Ohm = 30.77 Amps with all four heaters on.
240 Volt x 30.77 Amps = 7,384.8 Watts.
As the temperature of a metal rises, so does the resistance to current in that metal, heater, element, or lamp filament, I do not know what it is for these elements, but a light bulbs resistance can rise 15 times the cold filament resistance when heated.

Now if we heat these coil elements the resistance of the metal in them goes up considerably from what resistance the cold element has, this will give us a Lower amp reading than our (cold) calculations, and a lower wattage than our calculation here with cold elements.



Edit (thinking backwards again)


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## ericrm (Jan 14, 2013)

butcher said:


> each heating element is 10.4 ohm , and theyr is 3 heating element by infinite switch
> *The green wire is it just earth ground?*yes
> 
> *Why would you want to convert the furnace to 11O volt, it would be better to leave it 240 volt.
> ...


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## Geo (Jan 14, 2013)

ericrm said:


> butcher said:
> 
> 
> > each heating element is 10.4 ohm , and theyr is 3 heating element by infinite switch
> ...



theres a trick to getting the voltage you need. find a 3 phase motor (a 10 HP will work if you can find one) and use a gasoline engine to turn it.put 110v on one of the three phase fields and 220v will be generated from the other two fields, 110v for each field. furniture companies and other small manufacturing places that need more power than is supplied use 100 HP motors and just draw what they need.one 100 HP motor can generate enough power to run ten 10 HP motors or twenty 5 HP motors. ten HP should run a 220v kiln.


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## Jimmy (Jan 14, 2013)

Geo said:


> ericrm said:
> 
> 
> > butcher said:
> ...



Huh?? :shock:


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## Geo (Jan 14, 2013)

Jimmy said:


> Huh?? :shock:



:lol: i take it you have never heard of this before? an electric motor is just a generator in reverse.the reason you cant use a 110v or 220v two phase to do this is because theres no extra field to charge.it takes energy to make energy.older generators (and even newer ones) have heavy earth magnets for the magnetic fields and doesnt need to be charged.i would have to type a book to explain it all.Google how to convert a 3 phase motor to a generator.


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## butcher (Jan 15, 2013)

Geo, 
The motor would not act as a step up transformer, or step up the voltage, it could not change 120 volt to 240volt, although you can change single phase voltage to three phase voltage, 240 volt single phase to 240 volt three phase for example by using a "pony motor" like you are talking about. Actually the third phase generated with this motor would be slightly lower voltage than the other two phases when running due to motor loses. 

Generating three phase from single phase can also be done with a bank of capacitors.

A step up transformer (boost transformer), steps up the voltage, but with the transformers there are loses, and the primary current would have to be sized big enough to be able to supply secondary current needed for the furnace, this would mean an awful large transformer and primary wireing, that would make this too costly here.

Unless you were going to make a really small furnace out of the big furnace I would keep them at 240 volt.

Lets look at converting this furnace:

We want to keep the same wattage (HEAT), for example we will use an 8KW furnace kiln:

8,000 Watts / 240 Volts = 33.333 Amps
Now
8,000 Watts / 120 Volts = 66.666 Amps

Almost all houses are wired for 120/240 volts single phase here in the US, (other countries usually use the higher voltage 220 or 230 volt as the primary voltage depending on country).

Are you sure You cannot use these at 240 volt, even if you had to move the location, another thing to consider these are pottery kilns, I doubt they would make good kilns for melting small lots of gold, I think for one thing their large size, the waste of energy to heat the large kiln, life of the elements...


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## Geo (Jan 15, 2013)

http://www.ehow.com/how_6376682_use-phase-induction-motor-generator.html

http://www.ehow.com/how_8016485_rewire-motor-generate-ac-current.html

http://answers.yahoo.com/question/index?qid=20080321040405AAtnwaw

these are just the first three examples when i searched for it. im sure i can find a schematic for how to build what i described as ive seen it myself in operation. im not an electrician and cant explain why it does it but i do know that each of the two remaining fields on the motor produced 1/2 of a 220v circuit.

im going to see if i can find a youtube example.


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## Geo (Jan 15, 2013)

this video is very close.he is using two fields in the motor to generate power on the third.its converting 2 phase into 3 phase.it is the same concept to use single phase and convert it to 2 phase by energizing one field and generating power on the two remaining fields.the only difference is you will have to turn the motor with another motor to produce power.

[youtube]http://www.youtube.com/watch?v=8Qvjv23yDhA[/youtube]


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## butcher (Jan 15, 2013)

I am a licensed maintenance electrician I work with industrial voltages and three phase power.

Any three phase motor, when running on three phase, if it lost one phase while running will keep running (single phasing), the third phase is generated by the motors fields, but if this motor quits running and tries to start back up (on single phase) the motor windings would burn out, without the motor moving the third phase would not be generated, the motor could not begin running (although it would try), and the windings would overheat.


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## Geo (Jan 15, 2013)

thats why you have to keep it spinning with another motor (like a gasoline engine). i worked for a man named Buster Poole,true story, and this guy was so cheap he didnt want to buy electricity from the utility and set up a couple of these to run his furniture shop and used diesel motors to spin them. heres the cheap part, he was using untaxed diesel he was buying for his farm.they ran the whole shop on a standard 220v residential service.


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## butcher (Jan 15, 2013)

He could have saved some of that untaxed diesel fuel, once the three phase "pony motor" was moving up to speed it would run on single phase (generating the three phase to his shop), at that point he could have turned off the diesiel engine.
Although he would have to have some type of clutch, So his "Pony three phase motor" would not have to try and turn the diesel engine.


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## ericrm (Jan 15, 2013)

butcher said:


> Geo,
> The motor would not act as a step up transformer, or step up the voltage, it could not change 120 volt to 240volt, although you can change single phase voltage to three phase voltage, 240 volt single phase to 240 volt three phase for example by using a "pony motor" like you are talking about. Actually the third phase generated with this motor would be slightly lower voltage than the other two phases when running due to motor loses.
> 
> Generating three phase from single phase can also be done with a bank of capacitors.
> ...


butcher you manadge to give me all the tool and knowledge i needed for that project , when ill finish it ,i will show the pictures. thank again


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## Jimmy (Jan 15, 2013)

Geo said:


> Jimmy said:
> 
> 
> > Huh?? :shock:
> ...




A electric motor can be used as a generator but not both at the same time. The field is induced onto the rotor from the rotating field in the stator. First of all the field that is induced onto the rotor is not strong enough to generate much power on the stator windings, Secondly what would be induuced is mostly canceled out by the existing flux in the stator windings and the improper orientation of the magnetic core and non existance of any magnetic core in the stator. I can go on and on about this untill your head hurts with all the calculus. Maxwell is my friend.  
Most generators that are designed to make any power do not have any earth magnetics in them. Generally the residual flux that is retained in the core is sufficient to cause excitation of the field then more power is drawn from the produced current to provide the level of power necessary for proper regulation of the output.


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## ericrm (Jan 23, 2013)

here is the latest result of my tool
first the picture...




safety concern,very important, i have one plug to do everything with a bunch of wire on it... very bad idea ... so no 220 for me, and now im even stuck with 110 problem.

for the furnace i feel a bit desapointing on the performance , this is only a test run to see if it would work as it where suposed to on paper. i did manadge to get heat able to melt gold after 1:30h of waiting(i think i could do better as i still have some badly insulated crack and spot

the probleme is about oxygene ,i was hoping to be able to do fire assay with it ,but it have such an hard time getting to temp that if i was to open the door to let air in ,the furnace would not be able to compensate for the heat loss.

on a positive note it is very cost effective to run

thank you again for the help Butcher


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## butcher (Jan 23, 2013)

Yes be careful with electrical, working with those hot wires on a cluttered bench, it might short something out, or would make it easier to get electrocuted, or worse burn your shop down.

Glad to here you made it work, even if it did not work as you expected, you have learned a lot in doing this experiment, how heavy are the fire brick, are they absorbing or reflecting the heat (there are different kind of refractory brick for different purposes), looks like you had a loose connection on that GFCI outlet.

The furnace looks good, but I have to say it did give me a chuckle to see the duct tape around it (well who cares what it looks like if it done the job).


Thomas Edison learned more from his failures than he did with his successes.

Great job you done a nice job on building the furnace.


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## ericrm (Jan 23, 2013)

fire brick are very light, very isolating after 2 hour running the ouside was only warm to the touch . now that i know it work slowly but work. i will probably finish it with a layer of ceramic wool just to make sure...
i was thinking about something, could i use high heat concrete to make a removable cube to separate heater element from the oxide and fume and possible contact ,or is it not resistant enuf. i have read that some fondry use concrete in arc furnace . any info ?


edit : i tough concrete was refractory... so my question would be can i mold into a hollow cube some kind of refractory to protect the element?


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## Jimmy (Jan 23, 2013)

Castable refractories

Not cheap thou.
Here is a blace that will deal with hobbiests
I think what you are trying to do is make what is called a retort.

http://www.budgetcastingsupply.com/Castable_Refractory_Kast-0-Lite-26-LI.php


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## ericrm (Jan 23, 2013)

Kast~O~LITE© is a castable refractory cement manufactured by A.P. Green / Harbison-Walker. It is used as the insulation material in foundry furnaces and forges.

thank jimmy but this is the oposite of what i want :lol: , i want a material that let heat pass tru it to be able to melt the material inside without allowing the fume and other to make contact with the element . a good image would be the crucible in those bench top furnace that everybody here hate lol . or if it sound more simply i want to melt in a crucible that will be in a crucible(but that crucible is used to protect the heating element...clearer? :lol:


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## butcher (Jan 24, 2013)

I think most anything put on the elements would somewhat insulate them, also they need to expand and contract as they heat and cool, a ceramic wash coat could be used but it would insulate some, and I do not see any benefit, this would make heater replacement more difficult also.


Did you take amperage readings, and calculate wattage of your furnace, How many elements, cold resistance of the elements used, I am just curios of some of the details of your construction.


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## ericrm (Jan 24, 2013)

Butcher i used only one element that i have stretched at around 100" long, the cavity is 6" by 7.5" minus the ceramic plate on bottom. i have putted the heating element at 1/2 " distance from each other. the cold resistance is 10.4 ohm for a wattage of 1163 watts and expected amp 10.57amp .since my multimeter can not go higher than 10 amp i can not measure it.


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## Smack (Jan 24, 2013)

No 220v service in Canada? It's standard here in the states.


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## ericrm (Jan 24, 2013)

every house has 220v but it would cost me too much to bring 220v in my work place... i would have to add a new 100 amp box beside the old one ,than put about 100 feet of undeground cable, plus the digging 
and since i wish to get in a real shop someday, i see no point of putting a few thousand $ in a place that i will leave behind... also... i dont have a few thousand to put on electricity ...


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## bigjohn (Jan 24, 2013)

Imagine the kiln you could run with this.
480v 2000kw
Sorry just had to share this after reading the motor/generator post


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## ericrm (Jan 24, 2013)

with that much power f... the kiln, im going to a 3 foot large arc furnace :lol: :lol:


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## Jimmy (Jan 31, 2013)

I kept forgetting to mention this but you can put your elements in Fused Quartz tubes. This will keep them out of the kiln atsmophere.

http://www.technicalglass.com/product_pages/fused_quartz_tubing/fused_quartz_tubing.html


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## JHS (Jan 31, 2013)

just wondered if a used generator from craigs list would be simpeler


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## butcher (Feb 1, 2013)

With the cost of fuel to run the generator, I would bet building a fuel fired kiln would be a cheaper way to burn that money (I mean fuel).


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## Jimmy (Feb 1, 2013)

Made this in Africa to batch melt copper ingots. 







Small charcoal cupola to reduce various ore samples.


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