Re: Commercial Load Calculations
This is not an all-inclusive procedure for sizing a service to a non-dwelling occupancy. Please reference Article 220 for exact code specifications.
STEP 1 Use Table 220.3(A) (2005-220.12) and multiply lighting load va to total square footage. Feeder conductor at 125% for continuous load.
STEP 2 Demand load for motel, hospital, warehouse. (Table 220.11) (2005-220.42) All others at 100%.
STEP 3 Compare heat with A/C. Omit smaller. (220.21) (2005-220.60)
STEP 4 Heavy-duty lampholders at 600va each. (220.3(B)(5)) (2005-220.14(E))
Other outlets at 180va each. (220.3(B)(11)) (2005-220.14(I))
Multioutlet assemblies each 5-foot at 180va each. (220.3(B)(8)) (2005-220.14(H))
Show window lighting each linear foot at 200va each. (220.3(B)(7) (2005-220.14(G))
STEP 5 Demand for receptacle loads over 10kva. (220.13) (2005-220.44)
STEP 6 Demand for kitchen equipment. (Table 220.20) (2005-220.56)
STEP 7 Largest motor increased by 25%. (220.14) (2005-220.50)
STEP 8 Size the service by dividing the total va by the applied voltage. Use Table 250.66 to size grounding conductor. (It cannot be smaller than the neutral)
Bryan P. Holland, MCP
NEMA - Codes & Standards