size of kiln for 120V

[Paulette]

I am thinking of having a kiln built by Olympic. 17" square to run on 120v (I think that's what house current is). It will be 6" deep and have elements in top and sides. Are there any drawbacks to this? Obviously they don't sell them, so what would the reason be? Too long to heat up? Not even heat? I appreciate all the help I can get...I'm a total beginner on fusing.

It needs to be totally portable because I will take it back and forth with me between FL and PA. I live in a condo at both places, so I don't want to use 220. I plan on putting this in the den. Is there a problem with using them inside the house?

Thanks in advance for your help and suggestions,

[Bert Weiss]

I'm very interested in hearing practical news of what does and does not work relative to a 120 volt kiln.

[Riverviewglass]

I have a Paragon 120 volt - 13 inch round shelf - which can be transported back and forth - but it does weight 40+ pounds - that is one drawback - but is doable.
As to using the kiln in your den or anywhere in your condo - if you use fiber paper you will get a horrific smell - and also an odor from fresh kiln wash although not nearly as bad - so that could be a problem - also is the area where you are going to put the kiln well ventilated and away from anything flamable - drapes, carpet, etc.
Just some things for you to think about. Kim

[Paulette]

I have a 9" af99 from Arrow Springs for beads, I just want something I can make dishes and plates in...thought 17" square would be pretty basic size. I know the safety procedures...I do lampworking...but really need help with fusing! Just wonder if the size of 17" is too large for 120V to do a good job.

[Phil Hoppes]

Looking at the basic's. A kiln is simply a box you put heat into.
For any given kiln the amount of heat you need to put in is
dictated by:

1) the volume/size/mass of both the kiln and object
to be heated.

2) the loss of the kiln.

And the third point is:

3) The rate that you can heat a kiln is dictated by the number of heating elemets.

Items 1) and 2) will tell you how much power is required heat a specific item to a desired temperature and hold it for a specified amount of time. They are INDEPENDENT (it does not matter) of how the heat is put into the kiln. That is to say, items 1) and 2) above have nothing to do with the heat source in a kiln.

OK, now, with that understanding there really is no difference between a 110V kiln and a 220V kiln. This leaves us with the third point. The rate of heat transfer from the elements to the kiln is dictated by the specific design of the kiln and the elements that are used. Again going back to the basics items 1 and 2 will give you the power required to heat your kiln. Let's use my Paragon 24" front loader as an example. My kiln requires 10KW, that is 10,000 Watts of power. It uses a 220V service so from the simple equation:

P = VI or Power = Voltage x Current

you get:

10,000 Watts = 220 Volts X Current or

Current = 10,000 Watts/220 Volts = 45.4 Amps.

This is why my kiln is on a 50Amp Breaker.

If we wanted design this kiln using 110V service it would be quite simple from a paper design perspective. The current required would be:

P = VI or

10,000 = 110/I so the

I = 90.9 Amps.

The problem is from the practical perspective. For a normal house wiring system the maximum current allowed in any circuit is 50Amps. (Usually and I'm saying normal) A 50Amp circuit requires #8 wire for a run of 50' or less. For those not of a wiring mind #8 is BIG FAT WIRE.......and since it is normally a 4 wire circuit for code you have 3 #8 wires along with a fourth #8 or #10 ground wire in the bundle. This is both expensive and difficult to work with. It is still what I would call "off the shelf" however. Anything you would need to run the circuit I just described can be picked up at Home Depot.

Now lets look at our 110V design. For starters since the kiln requires 90.9Amps just to run we are talking about a 100 Amp service. I don't have my code book by my side but suffice it to say that the wire required for 100Amps is huge, expensive and not at Home Depot.

No need to go into further detail. The point is simply with a 110V system vs 220 V system for the same kiln the 110V will require twice the current. (all other things assumed to be equal). As the current requirements rise above a certain practical limit the only option left in a residential envrionment is to adjust to the next available higher voltage, which in the US is 220V. This is the reason why there are so many 220V systems for all kilns and in particular for the larger kilns. Another reason is most house wireing in the US on a 110V system is either 15Amp or 20Amp. If you are a kiln manufacturer and you want to make a 110V kiln you will be limited to a 1.6KW (15Amp) and a 2.2KW (20Amp) design. All kilns you want to sell at this power level will be dictated by this limitation. In this case, the 2.2KW limit calculated backwards will give you the approximate largest volume for your kiln. You can probably design a larger kiln at 2.2KW if it has very high insulation properties. That being said, it will take you for ever to cycle the kiln as, in the absence of any external cooling assistance, it will take a very long time to cool down.

Hope this helps.

Phil

[Tony Smith]

Phil's analysis is correct based on the power consumption of his Paragon kiln. There are ways to reduce the heat losses from a kiln thereby making them more efficient. Not all kiln manufacturer's are interested in taking the additional steps necessary to make their kilns more efficient.

With that said, if you are interested in making plates and bowls, consider Evenheat's new addition, the "hot spot". http://www.evenheat-kiln.com/glasskilns ... otshot.htm. It's 14½" diameter by 6½" deep and runs on a standard 15 Amp wall outlet, has top elements and has a 3 button Bartlett controller with 4 user-programmable programs. I saw one last week and it is a sweet little kiln and quite portable.

Tony

[charlie]

nec code (in the US) states that one shouldn't run a circuit at more than 80% of rating past a startup time.

phil, you should have a 60amp breaker and associated wire for 60amps for your kiln.

a 91 amp kiln would require a 120 amp service. a lot of older houses only have 100 amp service, so would be more than the entire house runs on. go look at the cable going into your house. for 200 amp service, it's about as thick as your wrist.

it is also cheaper to run a 220v kiln than a 120v kiln. you get less electrical loss due to the thicker wiring, and thus you wind up using less watthours, and thus it's cheaper in the long run.

[Phil Hoppes]

Charlie,

Paragon spec's the breaker for the 24" front loader at 50Amp. I'm guessing it is probably less than 10Kw so that it fits your recommendation as the plug that comes attached is a standard 50Amp/240V 3 wire plug. 60amp is probably better wrt not tripping out. Actually, the problems I'm currently having is my studio/garage is connected to the house so if Lynn is inside baking a turkey and I'm out in the studio baking a load of glass the Paragon often trip's off with a PF (Power Failure) indication. Navopache electric is pretty variable so if you happen to catch them on a down day with cooking in the house and the studio, be prepared for brownout. I'm adding an addition to the studio and with that addition, a dedicated 200Amp service just to the studio. That should at least cut out the "baking cookies" brown out syndrome.

Phil

[Paulette]

Wow! Thank you so much for the "more than ample explanations"! Looks like I should go with the 220 then. I guess I'll have him make me the 17" square with a circuit that will work from the dryer plug! Thanks guys, I really appreciate your help.