I was reviewing the exam guide at http://www.ncarb.org/en/ARE/~/media/Files/PDF/ARE-Exam-Guides/BS_Exam_Guide.pdf and Came across #17
The question is: A developer wants to construct a 15 story office bldg with approximately 10,000 SF of gross floor area per floor. Which of the following electrical distribution systems would be best to meet the developer's requirements and be most economical in terms of initial cost as well as later operational costs?
A. 120/208v, 3 phase, 4 wire
B. 120/240v, single phase, 3 wire
C. 120/240v, 3 Phase, 3 wire
D. 277/480v, 3 Phase, 4 wire
The answer is D.... Can anyone explain why?
Is it because feeder sizes are smaller?