More efficient lighting within buildings oftentimes doesn’t need as much electricity current flowing to it—and now, the 2020 National Electrical Code reflects that.
The list of commercial occupancies within Table 220.12 of the 2020 NEC has been revised to align better with the occupancy types in energy codes established by American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE), according to Derek Vigstol, senior electrical content specialist with the National Fire Protection Association in Quincy, Mass.
The values based on volt-amperes per unit of area have also been revised to align better with lighting density values determined through case studies performed in the various occupancies, Vigstol wrote on the association’s blog.
The changes to the table—which has received minimal revisions since the 1970s—were necessary to reflect updated building requirements for more efficient lighting, according to L. Keith Lofland, director of education, codes and standards for the International Association of Electrical Inspectors.
The revisions “result in reducing the lighting loads in some of the occupancies identified in the table based on technology enhancements over an almost 50-year period of time from the inception of this lighting load table,” Lofland wrote in IAEI Magazine. “Comprehensive data has historically not been available to support a revision to this table. Energy codes adopted across the country have created further discussion around the appropriate values.”
The lighting power density values from the 2020 cycle of the ASHRAE Standard 90.1 establishes a minimum margin of 25% between the maximum values determined through field studies and the new values for Table 220.12, he wrote. All but four occupancies are reduced to more closely align with actual use based on the field case studies conducted by the ASHRAE Lighting Committee. The four occupancies that now have higher lighting load values are gymnasiums, manufacturing facilities, religious facilities and warehouses.
Thomas Domitrovich, a national application engineer with Eaton Corp. in Pittsburgh who sits on NFPA Code Making Panel 2, contends that NEC 2020 load calculation changes can make infrastructure budgets more efficient and increase safety.
“The changes help the design engineer reduce the size of electrical distribution equipment where permitted by the design goals. This could translate into less wire and other related gear,” Domitrovich wrote in Machine Design magazine.
“With that, a focus on providing safety technologies for our electrical workers will hopefully grow,” he wrote. “Funding originally intended for power distribution can be reallocated to safety solutions for branch, feeder and service entrance equipment.”
Vahik Davoudi, an associate principal at Arup in Los Angeles believes that the changes to 2020 NEC’s Table 220.12 “are significant steps in the right direction to reduce the electrical service size and thereby cost of equipment.”
The newly introduced exception No. 2 expanded the allowance outlined in Exception No. 1 introduced in 2014 NEC, which allowed lighting loads to be calculated based on energy code adopted by local authorities while meeting certain conditions, Davoudi wrote in Consulting Specifying Engineer magazine. The 2020 NEC now permits the unit lighting loads in Table 220.12 for office and bank areas within the building to be reduced by 1 volt-ampere per square foot.
“Hopefully, the type of occupancies listed in exception No. 2 will expand in the near future to avoid having many buildings or tenants with oversized service,” he wrote.