Re: calculation for apartments
It usually is not the responsibility of the utility company or the building department to assist contractors on load calculations. They may enforce certain requirements and assist in meeting those, but the calculations are well within the scope of the contractors responsibilty. Service calculations are found in Article 220 of the NEC. The code allows certain amounts of total load reduction when sizing the service and service conductors. These reductions are called demand factors. The basis of these demand factors are that while the individual branch circuits will see the total connected load of the equipment they serve, services will most likely not. For example, what are the chances that all 4-apartments will have their ranges on full heat, the dryers going, and all the lights on at the same time. The contractor possibly used 220.32 for determining this service size. Table 220.32 shows a total reduction of total connected of 45% for 4 units. So if the units require 100-amp, 400-amp x 45% = 180-amp. 2/0 will handle this load per 310.15(B)(6).