Final answer:
To determine the number of circuits needed for a 3000 sqft. house, multiply the area by 3 watts/sqft for a total of 9000 watts, then divide by the maximum wattage per 15-amp circuit (1800 watts), resulting in 5 circuits required.
Step-by-step explanation:
To calculate how many single-pole 15 ampere branch circuits are needed for lighting in a 3000 sqft. house with a 120/240 volt service, one must first consider the National Electrical Code (NEC) or local building codes, which typically suggest a rule of thumb of providing 3 watts per square foot for lighting and general purpose outlets in a living space. Following this guideline:
- Calculate the total wattage required for the space by multiplying the area (3000 sqft) with the suggested wattage per square foot (3 watts/sqft), giving us 9000 watts in total.
- Since each 15-ampere circuit can handle up to 1800 watts (15 amps × 120 volts), divide the total wattage by the wattage per circuit (9000 watts ÷ 1800 watts per circuit).
- The result is 5 circuits needed to support the total lighting load without exceeding the capacity of each circuit.
Therefore, the correct answer is a) 5 circuits.