Multiple Ranges - Electrician Talk - Professional Electrical Contractors Forum

EvilBunny · 02-26-2009, 09:10 AM

A dwelling unit has 5 cooking appliances:

9 kw
10 kw
14 kw
16 kw
24 kw

What is line load calculation.

Using note 2 of table 220.55 I came up with 24k

My instructor is telling me that it is 23.6k

I think he is wrong. Is he?

electricista · 02-26-2009, 04:48 PM

Quote:

Originally Posted by EvilBunny

A dwelling unit has 5 cooking appliances:

9 kw
10 kw
14 kw
16 kw
24 kw

What is line load calculation.

Using note 2 of table 220.55 I came up with 24k

My instructor is telling me that it is 23.6k

I think he is wrong. Is he?

Well I tend to agree with you but I really suck at these. How did he get 23.6. Seems like he missed the part where the first two ranges must be 12Kw but I still can't get 23.6.

collin.thomas · 02-26-2009, 06:08 PM

I came up with with 24KW

12+12+14+16+24=78

78/5=15.6

15.6-12=3.6 rounds up to 4

4*.05=.2

5 ranges in col. C=20KW

20*1.2=24

I don't see how he could have come up with 23.6... make him show his work.

I found it...

He did not round for the major fraction...

15.6-12=3.6

3.6*.05=.18

20*1.18=23.6

EvilBunny · 02-26-2009, 07:02 PM

NEC 2008 Table 220.55 Note 2 states:

Quote:

...Then the maximum demand in Column C shall be increased 5 percent for each kilowatt or major fraction thereof by which this average value exceeds 12kW.

The "major fraction thereof" is where the point of contention is. I guess the interpretation is that since it doesn't say "round up" then it means that you just take 5% of whatever is left over after the 12kW?

I'm not sure what else it could be.

Is there a place in the code where we're told that a "major fraction" means to round up?

collin.thomas · 02-26-2009, 07:27 PM

Well the way my instructor explained it is:
5 percent for each kilowatt 5 percent for each major fraction (being .5 or more)

not

5 percent for each kilowatt5 percent of each major fraction

If your were supposed to take 5% of the fraction, why would it state major fraction.

EvilBunny · 02-26-2009, 07:36 PM

Agreed.

This is obviously the way it's supposed to be calculated. 24k has to be right.

Thanks.