Ranges

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rpb

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could someone give me an accurate answer to the following question and what your formula was.feeder demand for 1/8kw,1/9kw,1/12kw,1/15kw 120/240v single phase.thanks!
 

peter

Senior Member
Location
San Diego
Re: Ranges

Assuming that this is obviously not a test question, I ran your numbers [1/8kw,1/9kw,1/12kw,1/15kw] thru my little calculator in accordance with Table 220-19 and footnote #2. I came up with 17.85 kW which rounds up to 18 [for what its worth].
For some reason it says "using 12 kW for any range rated less than 12 kW". I don't know why this is. So 12 + 12 + 12 + 15 = 51 divided by 4 = 12.75.
Then the demand factor for four ranges is 17kW.
Since 12.75 is more that 12kW by nore than 1 kW,then 5% [.85kW] is added to the 17 =17.85.
Question? What do you do about a range exceeding 27 kW?
For the feeder demand, it would be exactly 81.13 amps for 220 volts or 74.37 amps for 240v (which the handbook uses).
Note: I realize some moderators don't like test questions unless the student has put some initial effort into solving it him/her-self.
Opinion: I think this section is a lot more complicated than it needs to be and should be totally redone from a blank state. Will Bennie agree with this? Demand factors are guesses and then you end up with an accurate guess to two decimal points.
~Peter
 

rpb

Member
Re: Ranges

Hi Peter,thanks for the reply!I just took my master exam and this was one of the questions.
unfortunately this one stumped me and a few others
after discussing this question with others that took the test there was at least 4 different anwsers we came up with.This article is way to vague for accurate anwers,especially when you dont perform these calculations every day.
 
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