Single-Phase cooking equipment on three- phase service

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chuckgassmannm

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el paso tx el paso
Hey there. I'm studying for my Master's Exam and reviewing my Mike Holt course. The example question says. What's the demand load for twenty single- phase 14 kw 208v ranges on a three- phase service? My question is how do they come up with 7 ? Divide 20 units by the 3 phases ? Thank you.

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petersonra

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Northern illinois
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chuckgassmannm said:
Hey there. I'm studying for my Master's Exam and reviewing my Mike Holt course. The example question says. What's the demand load for twenty single- phase 14 kw 208v ranges on a three- phase service? My question is how do they come up with 7 ? Divide 20 units by the 3 phases ? Thank you.

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14 kw * 21 ranges is 280 kw or about 816 Amps per phase

I don't know where they came up with seven either.
 
david luchini

david luchini

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chuckgassmannm said:
Hey there. I'm studying for my Master's Exam and reviewing my Mike Holt course. The example question says. What's the demand load for twenty single- phase 14 kw 208v ranges on a three- phase service? My question is how do they come up with 7 ? Divide 20 units by the 3 phases ? Thank you.

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7 would be the maximum number of ranges connected between any two phases (Yes, divide 20 by 3, and round up). The calculation would be based on twice that, or 14 ranges.
 
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david luchini

david luchini

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petersonra said:
the Op said the answer given was "7". I have no idea where that came from.
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I don't think 7 was the answer given, I think 7 was part of the process to get the answer, but the OP didn't know how they got the 7.
At least that is what I got from his question.
 
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chuckgassmannm

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el paso tx el paso
david luchini said:
Out of curiosity, what is the answer in the review course?
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The answer is 48 kw. Step 1: determine the maximum number of ranges between any two phases: 7 units. Step 2: Apply table 220.55 demand for twice the maximum number of ranges between any two phases: 7 units x 2= 14 units: 29kw. 14 kw range exceeds 12 kw by 2 kw. Increase the c column 29 kw by 5% for each kw in excess of 12 kw. Demand load =29 kw x1.10. Demand load =32 kw. Step 3: Demand load per phase: 32 kw/2 phases= 16 kw. Demand load for three phases= 16 kW x 3. Demand Load for three Phases= 48 KW.

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