The general lighting load per NEC Table 220.42(A) is used in which unit for expressing the load?

The general lighting load per NEC Table 220.42(A) is used in which unit for expressing the load?

• A. Watts per square foot (W/ft2)
• B. VA per square foot (VA/ft2)
• C. Kilovolt-amperes per square foot (kVA/ft2)
• D. Lumens per square foot (lm/ft2)

Answer: (B)

The general lighting load is expressed in volt-amperes per square foot (VA/ft2). This uses apparent power to represent the electrical demand for lighting, accommodating both real power and reactive power across different lighting technologies and ballasts. Using VA/ft2 keeps sizing consistent even when power factor varies, since it reflects the total electrical demand the service or feeders must carry. Lumens per square foot measures illumination level, not electrical load, so it isn’t used for sizing. Using watts per square foot would require knowing the power factor to convert to apparent power, and kilovolt-amperes per square foot is simply a larger unit of the same concept, whereas NEC standardizes on VA/ft2 for this table.

The general lighting load is expressed in volt-amperes per square foot (VA/ft2). This uses apparent power to represent the electrical demand for lighting, accommodating both real power and reactive power across different lighting technologies and ballasts. Using VA/ft2 keeps sizing consistent even when power factor varies, since it reflects the total electrical demand the service or feeders must carry. Lumens per square foot measures illumination level, not electrical load, so it isn’t used for sizing. Using watts per square foot would require knowing the power factor to convert to apparent power, and kilovolt-amperes per square foot is simply a larger unit of the same concept, whereas NEC standardizes on VA/ft2 for this table.