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Calculate how many single-pole 15 ampere branch circuits are needed for lighting in a 3000 sqft. house with a 120/240 volt service?

a) 5 circuits
b) 10 circuits
c) 15 circuits
d) 20 circuits

User Ineztia
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1 Answer

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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.

User Pitt
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