Multiple kilns

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jdping2

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I have 10 - 240 volt single phase kilns, each kiln draws 48 amps at 240 volt single phase . I need to size the panelboard which will be serving these kilns, I have unlimited power available in the main switchboard. Question- not considering space for future expansion, what is the minimum sized 120/240 Delta 3 phase panelboard amperage that I can use to feeed the 10 single phase 60 amp breakers ( kilns are 48 amp ea) . I cant find reference in the code book for kilns , so I am assuming these need to be calculated as continuous load, and yes, the end user will have all 10 kilns fired simultaneously Thank you!!

John D. Monterey ca
 
Since you have ten, you need to figure for twelve. 48a + 25% = 60a. 60a x 240v = 14,400va. 12 x 14,400va = 172,800va.
 
Just amplifying several points above:

Kilns very often run for extended periods of time, much longer than 3 hours.

However they are thermostatically controlled and thus the electrical load cycles on and off even though the kiln keeps running.

The third however is that a kiln might run for more than 3 hours as it is initially heating up.

I believe that determining if a kiln is a continuous load requires an analysis of the power rating of the heating elements, the insulation level of the kiln, and the thermal mass of the kiln. IMHO the greater the power rating for a given size of kiln, the less likely the kiln will be operating in a continuous fashion, whereas a highly insulated kiln with a low power rating will likely operate in a continuous fashion.

I do not know what actual practice is for commercially available kilns.

-Jon
 
electrofelon said:
I guess it depends on the definition of "on". The kiln may "on" for more than three hours but the elements will not be "on" that whole time.
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Wanted to edit my reply but got distracted and ran out of time. I don't think anyone has used the word "on" nor does the NEC definition of continuous load.

I agree with John, there are many variables: size, design, etc. That could make the heat heat up and cycling behavior vary widely. I have heard "and hour or two" frequently to reach temp, however I just texted an acquaintance who does pottery and she said 9 hours to reach 1900. That seems very long, I don't know if there are ramp rates involved or the element is indeed on full bore for that 9 hours. It probably is best to consider these continuous loads.
 
If one was really curious, you could take the thermal mass of the work, the insulation mass and thermal transmission, the input power, etc and work hour how much energy it takes to get to get a 1800c rise and work that against the insulation.

Or you could call the manufacturer and ask how long the elements run to get to full heat. (I do know from larger gas-fired kilns, that the burners would run full-bore for 10-15 hours before being throttled back. And that cone-based controllers just run until the cone sags.)
 
I think too much ink has been wasted on whether a kiln runs for more than 3 hours or not.

The bottom line for actual current used is this. If you go turn on 10 of those units, and you haven't used them in a week, they are all going to be firing at the same time. May only be for 30 minutes. It may be 2 hours. May be 4 hours. Who knows how long it will be before they all start cycling?

I think whether or not it's technically a continuous load is neither here nor there. They're all running long enough
 
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