article 220 calculations for nine 16kw ranges

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bill757

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Im having problems finding out how to calculate nine 16 kw ranges from article 220.55 can anyone explain it alittle more
 
bill757 said:
Im having problems finding out how to calculate nine 16 kw ranges from article 220.55 can anyone explain it alittle more
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I stink at it also but I will give it a try. I am assuming household ranges.

Find 9 ranges under the # of appliances then go over to Col.C

Now take a look at Note 1

See what you can do from there.
 
Seriously? That's a high-dollar apartment building.

I get 63,360 watts.

16,000 * 9 = 144,000 watts

column c for 9 ranges not over 12kw is 24%

note one says add 5% for each kw over 12, so that's an extra 20%

20% + 24% = 44%

44% * 144,000 = 63,360watts
 
mdshunk said:
Seriously? That's a high-dollar apartment building.

I get 63,360 watts.

16,000 * 9 = 144,000 watts

column c for 9 ranges not over 12kw is 24%

note one says add 5% for each kw over 12, so that's an extra 20%

20% + 24% = 44%

44% * 144,000 = 63,360watts
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Marc Col C is max demand not %
 
Dennis Alwon said:
Marc Col C is max demand not %
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That makes it even easier then. 44,000 watts. Groovy.

dorky04.gif


(why do you suppose they do dryers by %, and ranged by demand?)
 
mdshunk said:
That makes it even easier then. 44,000 watts. Groovy.

(why do you suppose they do dryers by %, and ranged by demand?)
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I still don't think that's correct. but I want the OP to try. How did you get 44000

I have no idea why the calcs are this way.
 
If i recall it right with the load demand and load caluations on both range and dryer with very large numbers of the appalinces there.,, not everything will be on the same time.

maybe twice a year everything will hit hard and find out the master breaker tripped or POCO transformer smoked from hevey load demand of range.

i hope it help some of it.


Merci, Marc
 
I disagree. 9 ranges in col. C gives us a demand of 24000 W. Now, if these were all 12 kw ranges we would take that demand at 100%. These are 16kw ranges so we need to add an additional 20% (5% for each kw over 12) to this to come up with (24kw X 1.2[120%])=28.8kw demand on the feeder.

Sorry Dennis, you posted while I was typing my response, I should have let Bill work on it a bit more.
 
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ray cyr said:
I disagree. 9 ranges in col. C gives us a demand of 24000 W. Now, if these were all 12 kw ranges we would take that demand at 100%. These are 16kw ranges so we need to add an additional 20% (5% for each kw over 12) to this to come up with (24kw X 1.2[120%])=28.8kw demand on the feeder.
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That's what I get but I did not want the OP to get the answer without trying.
 
Dennis Alwon said:
That's what I get but I did not want the OP to get the answer without trying.
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I'm sure it was homework, anyhow. What sort of building is going to have 9, 16kw ranges? A high end apartment building is all I could come up with, and even at this, it's going to be engineered.
 
Think about what's going to happen in this building on Thanksgiving, when only 29kw was allotted for ranges. :cool: A couple people throw in a few loads of clothes in the dryer, and some poor sap starts to come up in the elevator, and POOF! I know, the NEC is not a design manual. Good thing.
 
its in understanding the nec by mike holt i couldnt figure out how they came up with it it is 28.800w thankyou for explaining
 
mdshunk said:
Think about what's going to happen in this building on Thanksgiving, when only 29kw was allotted for ranges. :cool: A couple people throw in a few loads of clothes in the dryer, and some poor sap starts to come up in the elevator, and POOF! I know, the NEC is not a design manual. Good thing.
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I totally agree-- I did the calculation 3 times because I couldn't believe it was correct. 29 kw for 9 16KW ranges. Yikes
 
Dennis Alwon said:
I totally agree-- I did the calculation 3 times because I couldn't believe it was correct. 29 kw for 9 16KW ranges. Yikes
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That's why I felt pretty good about my original 63kw number. It felt right. I don't know if I've ever calculated range demand long hand, so it was a nice exercise.
 
Even myself i did check the calauation both shorthand and long hand and it land right on the nail as well.,, IMO i just don't like this number espcally with this large of range and the number of it as well i rather bump up more higher to cover the " Wiggy Room " factor [ if you get my idea :cool: ]

as what Marc Shunk mention about the amount of load it can make the whole place go dark unless you want to stare at Frog eyes when they blink on.

Merci, Marc
 
ray cyr said:
I disagree. 9 ranges in col. C gives us a demand of 24000 W. Now, if these were all 12 kw ranges we would take that demand at 100%. These are 16kw ranges so we need to add an additional 20% (5% for each kw over 12) to this to come up with (24kw X 1.2[120%])=28.8kw demand on the feeder.

Sorry Dennis, you posted while I was typing my response, I should have let Bill work on it a bit more.
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My calculation:

Column C for 9 ranges: 24kw
Note 1 (Demand in Column C inceases 5% for each KW over 12kw):
9x(16kw-12kw)x5%=1.8kw
Total Demand is 24KW+1.8KW=25.8KW.

Where you get the 20% factor in your post?
 
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