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Tuesday, September 27, 2022
Question:
Good Morning Code Question of the Day and thank you for keeping this operating every day of the year. We were given plans for a dwelling unit basement rec room buildout. The exterior walls are 12" poured concrete. The exterior measures 52' X 30'. When calculating the general lighting load at 3 Watts per square foot this computes to 4680 Watts. I would need four 15 ampere circuits. Section 220.12 says I have to use the outside measurements of the building. However, it also allows me to exclude areas "unused or unfinished spaces not adaptable for future use." What spaces are included in this exclusion? Would a 4' x 15 ' unfinished closet change my lighting calculation to 4500 Watts and then only need 3 circuits?
All the best,
Jeff Glanstein
A
Answer:
Jeff, glad to hear you enjoy the CQD service. You are correct in your application Section 220.12, as each floor's lighting load shall be calculated using the outside dimensions of the building. Section 220.12 does give some examples of the spaces that can be excluded from the calculation, specifically listing: open porches, garages, and space not adaptable for future use. The NEC® does not specifically define "adaptable for future use", but other Code sections may provide insight on the intent. One potential clue as to the intent can be found in Table 220.12, where there is a lesser kVA value given for calculating the lighting loads of: Halls, Corridors, Closets, and Stairways. However, these lesser kVA values are not permitted to be applied to one-family dwelling units. This would indicate the intent of the Code is to include closet's square footage in the lighting load calculations, using the full kVA value.