- Calculate General Lighting and Receptacle Loads (Line 1): Multiply the square footage of the dwelling by 3, then multiply by the number of units.
- Calculate Small-Appliance Branch Circuits (Line 2): Multiply 1500 by the number of units (minimum of two circuits per unit).
- Calculate Laundry Branch Circuit(s) (Line 3): Multiply 1500 by the number of units (minimum of one circuit per unit).
- Add Lines 1, 2, and 3 to get Line 4.
- If Line 4 is greater than 117,000, calculate Line 6: Subtract 117,000 from Line 4. Otherwise, skip to Line 8.
- Calculate Line 7: Multiply Line 6 by 25%.
- Calculate Line 8: Take the smaller value between Line 5 (if applicable) or 117,000, then multiply by 35%.
- Calculate Total General Lighting and Receptacle Load (Line 9): Add 3000 + Line 7 + Line 8.
- Calculate Fastened-In-Place Appliances (Line 10): Sum the volt-amperes of water heaters, dishwashers, and disposers. If four or more units, multiply the total by 75%.
- Calculate Clothes Dryers (Line 11): Use 5000 watts or the nameplate rating (whichever is larger). The neutral demand load is 70% for feeders.
- Calculate Ranges, Ovens, Cooktops, and Other Household Cooking Appliances over 1750 Watts (Line 12): Use Table 220.55 and applicable notes. The neutral demand load is 70% for feeders.
- Calculate Heating or Air-Conditioning System (Line 13): Compare heat and A/C, omit the smaller. For heat pumps, include compressor and maximum electric heat.
- Calculate Largest Motor (Line 14): Multiply the volt-amperes of the largest motor by 25%.
- Calculate Total Volt-Ampere Demand Load (Line 15): Add Lines 9 through 14.
- Calculate Minimum Amperes (Line 16): Divide Line 15 by the voltage.
- Determine Minimum Size Service or Feeder (Line 17): Use 240.6(A) based on Line 16.
- Size the Service or Feeder Conductors (Line 18): Use 310.15(B)(7) for conductors up to 400 amperes; higher ratings comply with Table 310.15(B)(16).
- Size the Neutral Conductor (Line 19): Can be smaller than ungrounded conductors if requirements of 215.2, 220.61, and 230.42 are met; must not be smaller than specified in Table 250.102(C)(1).
- Size the Grounding Electrode Conductor (for Service) (Line 20): Use Line 18 to find conductor size in Table 250.66. For Equipment Grounding Conductor (for Feeder), use Line 17 and Table 250.122.
Parent Tip: Review the logic above to help your child master the concept of standard electrical load calculation worksheet.
