optional calculation multi family

[DeepCreekElectric]

2008 NEC page 767 (application of Demand factor)
Question: Is the demand factor listed in the example D4(b) and Example D4(a) printed wrong? The listed demand factor is first 3000 @ 100% remainder @ 35%.. I thought all optional calculations we first 10,000 @ 100% remainder @ 40%?
Which way is correct. I thought 3000 @ 100% remainder @ 35% was for standard calculation only??

 

[steve66]

You are looking at the calculation for the feeder to each dwelling, which is calculated using the standard method.

The "optional calculation" is used (see page 768 for example D4b) to calculate the service conductors required for the entire building. In this example, they show the calculation for 20 apts. (38% demand factor) and for 40 apts. (28% demand factor.)

Steve