U.s 230v Electric Element,ok For Use Here,hertz Etc?

[uptou]

Hello,i'm looking to build a very small,basic electric kiln for a little hobby ive got going.After doing some research ive realised that it can be done using normal,sheathed,cooking stove or oven elements.

I can handle the wiring,but am i right in thinking that if i used 230v elements from the usa,the 60 hertz for the states,& 50 hertz for thailand would not make any difference or cause any problems for heating elements?

Thanks for any help given.

Edited December 12, 2007 by uptou

[GuestHouse]

They'll be OK on the Thai power supply.

[astral]

Moved as we have experts in this sub forum.

[naka]

No problem as it's a resistive load.

Naka.

[Crossy]

No problem as it's a resistive load.

Naka.

Yep ^^^

SHOULD be OK, my only reservation would be the element to sheath insulation, the US 230V supply is only ever 115V above ground (bi-phase split about ground), whereas Thailand's 220V is truly 220V above ground.

A cheapo element may not have sufficient safety factor. That said I'm sure it will be just fine, just worth bearing in mind

Edited December 13, 2007 by Crossy

[tuffy]

I have a similar question......(This was brought up in a different forum)

I have a roaster oven brought from the US. It is 110V and to buy a transformer is cost prohibitive as it requires at least 1450 Watts.

Is it possible to change the controller but use the existing element? I hate to give up on this one as it is the perfect appliance to roast a turkey or for that matter any other large hunk of meat!

[Crossy]

I have a similar question......(This was brought up in a different forum)

I have a roaster oven brought from the US. It is 110V and to buy a transformer is cost prohibitive as it requires at least 1450 Watts.

Is it possible to change the controller but use the existing element? I hate to give up on this one as it is the perfect appliance to roast a turkey or for that matter any other large hunk of meat!

There are two issues at work here:-

1. The controller probably relies on the mains frequency for timing, it will run slow (about 17% slow) on 50Hz, you can probably take account of that in your cooking timing, a small converter to run the controller will be required to take account of the differing voltage.
   
2. It MAY be possible to re-wire the heating elements for 220V, particularly if there are two. There could be loss of functionality (like you can only have both on together). HOWEVER this is a job for a competent appliance electrician.
   

It could be worth talking to your local appliance man, he may be able to source 220V elements that will fit which would be the ideal solution (along with the timer modification in 1. above).

If it were my oven I would have no hesitation about doing it myself, BUT, I am a skilled electrical/electronic engineer with 30+ years in the wide world of things that bite.

EDIT If this is a 'big name' appliance and therefore sold globally 220V 50Hz parts are probably available as spares, again visit the appliance man.

Edited December 13, 2007 by Crossy

[tuffy]

EDIT If this is a 'big name' appliance and therefore sold globally 220V 50Hz parts are probably available as spares, again visit the appliance man.

Crossy,

Here is what I have...

http://www.hamiltonbeach.com/products/roas...oven.php?page=1

I haven't seen this style available here though so i may hunt down my local repair guy and see what he can do

[uptou]

Thanks for the help.

My meter that runs my house is rated at 5(15) amps,standard volts.Does this mean that my kiln circuit would not be able to exceed the 15 amps without tripping the circuit breaker?

The max kiln temp i'm hoping for is around 735 centigrade.It wood be no bigger that 9x9x9 inches.

At the moment i'm thinking i'd like to run 2 stove or oven elements,one on each side of the kiln,off of simple oven infinite switches (i'm thinking one switch per element) or possibly a cheap controller.

Like most people I'm familiar with the formulas v=axr,w=axv,& also come from an enginering background (the big hammer sort),but can somebody guide me through the math?

I believe if i connected the elements in series i would get only half the heat on the second one inline?

If i were to connect 2 elements wired in parallel rated at 1500watts each,3000w/220v=13.63 amps drawn?

So is a 1500w rated element the maximum i could use for each element?

Thanks again

I was originally going to use the coiled type resistance wire like kanthal a1,but it was proving difficult to find firebrick,& then i'd have to cut grooves,which i'm not that keen on,but i suppose i could order ceramic rods off of the internet.

Edited December 13, 2007 by uptou

[Crossy]

I know little to nothing about kilns but a few things to ponder:-

Your 15A supply will max out at 3300W

Use more smaller elements for better control (turn off one or two to maintain temperature)

You will need GOOD insulation with only 3kW input

The kiln can't get hotter than the elements so go for ones that glow bright red in operation

Color Approximate Temperature

°F °C K

Faint Red 930 500 770

Blood Red 1075 580 855

Dark Cherry 1175 635 910

Medium Cherry 1275 690 965

Cherry 1375 745 1020

Bright Cherry 1450 790 1060

Since you're likely to be over-running regular oven elements (and killing the reliability) make sure they are readily available for when they fail and easy to change.

[uptou]

Yes,i was also thinking that the modern stove elements dont glow red hot,& get the heat to the pot by contact more than anything.Maybe i'd be better off with the oven elements.The advantage i believe with sheathed elements is that they would be virtually self supporting,& could be used with ceramic fiber insulation.Very basic in other words.

Decisions

Thanks

PS.ive heard from somebody that you can bend oven elements quite easily.Is that right?

Edited December 13, 2007 by uptou

[chownah]

I was originally going to use the coiled type resistance wire like kanthal a1,but it was proving difficult to find firebrick,& then i'd have to cut grooves,which i'm not that keen on,but i suppose i could order ceramic rods off of the internet.

Electrically fired ceramic kilns would provide the temp you want and they are commonly built with "sponge brick" more properly known as insulationg fire brick. It is rumored to be available in Thailand and I have even seen it listed on the internet by one of the Thai fire brick companies but I have never purchased any here. Look around on the internet and you can probably find the same thing that I saw. The insulating fire brick comes in different grades and densities with generally speaking brick that withstand higher temperatures being more dense and more expensive and less efficient as an insulator so you really want to buy the grade that is just as good as you need or maybe a bit better as going to a higher grade will cost more and be less efficient as an insulator and be harder to cut and work.

I built a mini forge using the lowest grade of insulating fire brick lined with castable refractory. It had a heating chamber shaped like a cylinder and I fired it laid on its side so the axis of the cylinder was horizontal. The chamber was about 15 cm (6 inches) in diametre and about 30 cm (12 inches) long. One end of the cylinder was enclosed with fire brick and lining and the other was left open. A small hole big enough to accept a hand held propane torch nozzle (like plumbers use to solder copper pipes) and oriented so that the flame entered tangential to the inner wall and about 10 cm (4 inches) from the enclosed end. The open end was used for placing pieces of steel to be heate into the kiln and I would stack lose fire brick to partially close it off while working so I could conserve heat when possible but open it wide for inserting larger pieces (large is relative...remember only a 15 cm diametre opening). I got some propane hose and fittings so I could run the nozzle off of a cooking gas sized tank. Even with just that tiny propane nozzle I could get steel as hot as anyone would want for forging....beyond bright cherry and well into orange....hot enough to melt brass which I did a bit of with a small crucible. This rig was slow to heat up (took a couple of hours to get up to full temp) but could keep me happily heating up steel and working it for two days or more on one tank of gas....I made candle holders...it worked great....I wish I had some time to do some of this here and maybe in the future I will but right now I'm a farmer.

Anyway, back to your project (sorry for the digress)....even the cheapest grade of insulating fire brick should be more than adequate for your needs but when buying it the spec will tell you what temp it is rated for so no need for guess work. These bricks are very very easy to work...you can cut it with a dull hand saw and file it very easily with a rasp....drill it with dull drills very easily. You could very easily cut channels to accept the coil heating wires with a hand saw...no problem....and assuming that you would use refractory mortar to assemble your kiln you would have a very very efficient rig I'm sure. If you can't make the electric thing work you might consider gas although it would take alot more playing around with it probably to get the heat right and evenly distributed but there would be no problem getting up to the required temp and the cost of fuel should not be much of a factor.

Edit: The heater wire that is used in oven elements and like what you can buy to use when making a custom kiln can be bent easily when cold BEFORE THEY ARE FIRED FOR THE FIRST TIME....but after they are fired once and cool then they become brittle and if you want to bend them then you must do it when they are hot....this is what I have heard but have never done it myself.

Chownah

Edited December 13, 2007 by chownah

[dotcom]

a 5/15 amp meter is the lowest & cheapest available. I would not suggest using it for your kiln. I would suggest upgrading (including the wires to the street) or move to a different place.

I used a 30/100 (including 16 mm wires) meter in my house but most new construction in LOS are 15/45 today & those are fine for most applications.

Hertz is only critical in applications concerning motors (like air cons).

For gentleman A. A transformer might be the cheapest & best option despite being expensive.

Edited December 15, 2007 by dotcom

[uptou]

I'm now looking for a digital or analogue temperature controller to run this kiln.Would a 240v model from the uk or the states,be ok over here hertz wise?

thanks for any help.