Required Number of Lighting Circuits – Nondwelling

Required Number of Lighting Circuits

The required number of lighting circuits is calculated for the connected load. The connected load is the load in volt-amps before any demand factors are applied. The connected load is the area inside a building in square feet multiplied by the required volt amps per square foot.

Table 220.42(A) provides the volt amps per square foot. This load is already sized at 125%. To determine the required current for the lighting load, divide the connected load by the voltage of the lighting load.

The voltage for the lighting load is usually 120 V or 277 V, but it may also be 208 V, 240 V, or 480 V. To determine the number of circuits, divide the load by the size of the circuit breaker (CB). CB sizes for general lighting loads are typically 15 A or 20 A. If the answer is not a whole number, round up to the next whole number.

For example, how many circuit breakers are required for the lighting circuits in a 50,000 sq ft manufacturing facility? The voltage for the manufacturing facility is 120/240 V, and 20 A CBs are used.

Step 1: Number of circuit breakers = 2.2 VA/sq ft x area of building / voltage

Step 2: Sum of Step 1 / circuit breaker rating

In the example :  2.2 VA x 50,000 = 110,000 VA / 120V = 916.66 / 20 = 45.83 – Round up to 46

Solution: Number of circuit breakers = 46

Note: The 2.2 VA per sq. ft comes from Table 220.42(A) in the 2023 National Electrical Code, it is 220.12 in earlier editions.