What is the minimum number of 120 volt, 15 amp branch circuits required for the lighting of a 4,200 square foot dwelling unit?

To determine the minimum number of 120 volt, 15 amp branch circuits required for the lighting of a 4,200 square foot dwelling unit, one must reference applicable electrical codes that provide guidelines for calculating the required circuits based on the square footage of the dwelling.

According to the National Electrical Code (NEC), the general rule for lighting circuits in a residential setting is to allocate a certain number of watts of lighting per square foot. For most residential applications, this recommendation is typically around 3 watts per square foot for general lighting.

In this case, for a 4,200 square foot home, the total wattage needed for lighting can be calculated as follows:

4,200 square feet × 3 watts/square foot = 12,600 watts.

Since each 120 volt, 15 amp circuit can handle a maximum of 1,440 watts (120 volts × 15 amps), the calculation for the minimum number of circuits needed would be:

12,600 watts ÷ 1,440 watts/circuit = approximately 8.75 circuits.

However, in practice and following the NEC guidelines, it’s generally rounded up and further safety factors and code requirements might suggest a higher total depending on additional factors such as load diversity