Are there any formal rules as to rounding when doing calculations?
In a practice workbook, the calculations are rounded to the tenths. When I do the calculations precisely (to the thousandths) my fractional answer is below .5, but the book's fractional calculation is .5 exactly.
This changes the answer I get versus what the book says is the answer.
I don't see anything in the NEC that calculations must be rouded to the tenths before applying 220-3(b).
I think the amount of rounding up or down depends on the magnitude of the answer. For example if an answer is 120.6 volts,it would be ok to round up to 121.If the answer is 0.555 amps,I would round it up to 0.56.I guess a lot depends on the required accuracy. Chris
Calculate the minimum size Type THW copper conductors required to serve the following motor loads from a 480/277, 3-phase, 4-wire service: Two 40-horsepower, 460 volt, 3-phase synchronous type, 90 percent P.F. and one 10-horsepower squirrel-cage, 460 volt, 3-phase motor at 100 percent P.F.
Roger, You used the 575 volt amp for the 40 hp. The 480 volt current is 52. Also what is the 1.1 multiplier for? I come up with 1.25(52) + 52 + 14 = 131 amps. This will require a #1 THW copper feeder. Don