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8.6 Commercial and Industrial Load Calculations

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Alaska Journeyman Electrician Study Guide Exam

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1 Chapter 1: Alaska Certificates of Fitness, Law & Exam Logistics

1.1 The Alaska Certificate of Fitness System 1.2 Journeyman Eligibility: 8,000 Hours and How Alaska Counts Them 1.3 Trainee, Residential Wireman, Lineman, Provisional & Reciprocal Certificates 1.4 The Journeyman Examination: Format, Scheduling, Open-Book Rules & Retakes 1.5 Adopted Codes, Fees, Renewal, Inspection & Enforcement

2 Chapter 2: Using the 2020 NEC

2.1 Article 90: Purpose, Scope, Arrangement & Enforcement 2.2 Navigating the Code Book: Structure, Index & Tabbing Strategy 2.3 Article 100 Definitions You Must Know Cold 2.4 Electrical Theory for the Exam: Ohm's Law, Power & Three-Phase

3 Chapter 3: General Requirements — Article 110

3.1 Approval, Listing, Interrupting Rating & Terminations 3.2 Temperature Limitations of Terminations — 110.14(C) 3.3 Working Space, Access, Egress & Illumination — 110.26(A) through (D) 3.4 Dedicated Equipment Space, Guarding & Over-1000-Volt Installations

4 Chapter 4: Conductors and Ampacity — Article 310

4.1 Conductor Types, Insulation Markings & Table 310.16 4.2 Ambient Temperature Correction and Alaska's Cold 4.3 Adjustment for More Than Three Current-Carrying Conductors 4.4 Putting It Together: Full Conductor-Sizing Problems 4.5 Parallel Conductors, Dwelling Service Sizing & Conditions of Use

5 Chapter 5: Wiring Methods and Materials — NEC Chapter 3

5.1 Article 300 General Requirements and Underground Cover 5.2 Thermal Movement: Expansion Fittings and Table 352.44 5.3 Boxes and Enclosures: Box Fill and Pull Box Sizing 5.4 Cable Assemblies: NM, MC, AC, SE, UF and TC 5.5 Raceways: RMC, IMC, EMT, FMC, LFMC, PVC and ENT 5.6 Conduit Fill: Chapter 9 Tables and Annex C 5.7 Cable Trays, Wireways, Busways, Gutters and Surface Raceways

6 Chapter 6: Branch Circuits and Feeders

6.1 Branch-Circuit Ratings, Conductor Sizing & Multiwire Circuits 6.2 Required Outlets and Receptacle Spacing in Dwellings 6.3 GFCI Protection — Article 210.8 6.4 AFCI Protection and Receptacle Requirements 6.5 Feeders and Outside Branch Circuits — Articles 215 and 225 6.6 Grounded Conductor Identification, Switches & Panelboards

7 Chapter 7: Overcurrent Protection — Articles 240 and 242

7.1 Article 240 Fundamentals: Ratings, Locations & Conductor Protection 7.2 Feeder Tap Rules — 240.21(B) 7.3 Transformer Secondary Conductors — 240.21(C) 7.4 Fuses, Circuit Breakers, Series Ratings & Article 242 Surge Protection

8 Chapter 8: Services and Load Calculations

8.1 Service Conductors, Clearances and Service Equipment 8.2 Service Disconnects, the 2020 Rule Change, SPDs and Service GFPE 8.3 Article 220 Part II: General Lighting, Receptacles and Demand Factors 8.4 The Standard Dwelling Calculation — Article 220 Part III 8.5 Optional Dwelling and Multifamily Calculations 8.6 Commercial and Industrial Load Calculations 8.7 Neutral Load Calculations and Harmonics — 220.61

9 Chapter 9: Grounding and Bonding — Article 250

9.1 System Grounding, 250.24 and the Main Bonding Jumper 9.2 The Grounding Electrode System — 250.50 through 250.53 9.3 Grounding Electrode Conductor Sizing and Installation 9.4 Bonding: Services, Metal Piping, Structural Metal and Other Systems 9.5 Equipment Grounding Conductors: Types, Sizing and Continuity 9.6 Separately Derived Systems and Separate Buildings 9.7 Ground-Fault Protection of Equipment and Grounding of Specific Equipment

10 Chapter 10: Equipment for General Use — NEC Chapter 4

10.1 Flexible Cords, Cables and Fixture Wires 10.2 Switches, Receptacles and Industrial Control Panels 10.3 Luminaires, Lampholders and Recessed Installations 10.4 Appliances and Fixed Electric Space Heating 10.5 Deicing, Snow Melting, Pipeline and Vessel Heating 10.6 Motors Part I: Full-Load Current, Conductors and Overload Protection 10.7 Motors Part II: Short-Circuit Protection, Controllers, Disconnects and HVAC

11 Chapter 11: Transformers, Generators and Special Occupancies

11.1 Transformers — Article 450 11.2 Generators, Storage Batteries and Energy Storage Systems 11.3 Hazardous (Classified) Locations — Articles 500 through 506 11.4 Garages, Hangars, Fuel Dispensing, Bulk Storage and Spray Application 11.5 Health Care Facilities — Article 517 11.6 Agricultural Buildings, Manufactured Homes, RV Parks and Marinas 11.7 Assembly, Theaters, Carnivals, Temporary Installations and Pools

12 Chapter 12: Special Equipment, Special Conditions and Exam Strategy

12.1 Signs, Cranes, Elevators, Electric Vehicle Charging and Welders 12.2 Solar Photovoltaic, Interconnection and Stand-Alone Systems 12.3 Wind Electric Systems and Fire Pumps 12.4 Emergency, Legally Required Standby, Optional Standby and COPS 12.5 Class 1, 2 and 3 Circuits, Fire Alarm, Optical Fiber and Communications 12.6 Cold-Climate Practice in Alaska: Code Basis and Engineering Judgment 12.7 Exam-Day Strategy: Navigation, Calculation Workflow and Time Management

8.6 Commercial and Industrial Load Calculations

Key Takeaways Explain This Topic AI

Table 220.56 applies commercial kitchen equipment demand factors of 100 percent for one or two units, 90 percent for three, 80 percent for four, 70 percent for five, and 65 percent for six or more, with the result never less than the sum of the two largest loads.

NEC 220.14(K) requires bank and office building receptacle loads to be the larger of the 220.14(I) calculation after Table 220.44 demand factors, or 1 volt-ampere per square foot.

NEC 220.43(B) requires 150 volt-amperes for every 2 feet or fraction thereof of lighting track in other than dwellings and hotel or motel guest rooms.

NEC 220.87 permits an existing feeder or service load to be determined from the maximum demand recorded over a minimum 30-day period, multiplied by 125 percent, plus the new load.

Continuous loads in commercial calculations attract the 125 percent multiplier when sizing conductors and overcurrent devices under 210.19, 210.20, 215.2, 215.3, and 230.42.

Last updated: August 2026

How Commercial Differs from Residential

Three structural differences drive commercial calculations:

Receptacles are counted individually at 180 VA each — there is no 220.14(J) blanket inclusion.

Most lighting is continuous , attracting the 125 percent multiplier at the conductor and overcurrent device.

The demand factors are far less generous. Table 220.42 gives "all others" 100 percent; only hospitals, hotels, motels, and warehouses get a reduction on lighting.

Lighting

Use Table 220.12 for the occupancy type, applied to the floor area. Then check 220.42 — for most commercial occupancies the demand factor is 100 percent .

Because store, office, and warehouse lighting typically operates more than three hours, the lighting load is a continuous load under the Article 100 definition. That means the conductor and overcurrent device are sized at 125 percent of it under 210.19(A)(1), 210.20(A), 215.2(A)(1), and 215.3.

The 125 percent factor is not part of the Article 220 calculated load. It is applied afterward when sizing conductors and devices. Keep the two operations separate on the exam: Article 220 gives you the load; Articles 210, 215, and 230 tell you how to size for it.

Receptacles — 220.14(I), 220.44 and 220.14(K)

Step 1. Count receptacle outlets and multiply by 180 VA each (or 90 VA per receptacle for a listed assembly of four or more on one yoke).

Step 2. Apply Table 220.44 : 100 percent of the first 10 kVA, 50 percent of the remainder.

Step 3. For banks and office buildings only , compare the result against 1 VA per square foot under 220.14(K) and use the larger .

Worked Example

An 8,000-square-foot office building has 96 duplex general-use receptacles on single yokes. 220.14(I): 96 x 180 VA = 17,280 VA

Table 220.44:

  • First 10,000 VA at 100% = 10,000 VA
  • Remaining 7,280 VA at 50% = 3,640 VA
  • --------
  • Calculated receptacle demand 13,640 VA

220.14(K) alternative: 8,000 ft2 x 1 VA = 8,000 VA

  • Use the LARGER = 13,640 VA
  • Commercial Kitchen Equipment — 220.56

It shall be permissible to calculate the load for commercial electric cooking equipment, dishwasher booster heaters, water heaters, and other kitchen equipment in accordance with Table 220.56 . These demand factors shall be applied to all equipment that has either thermostatic control or intermittent use as kitchen equipment. These demand factors shall not apply to space-heating, ventilating, or air-conditioning equipment.

However, in no case shall the feeder or service calculated load be less than the sum of the largest two kitchen equipment loads .

  • Number of units of equipment Demand factor (percent)
  • 1 100
  • 2 100
  • 3 90
  • 4 80
  • 5 70
  • 6 65
  • 7 65
  • 8–9 60
  • 10 and over 50

The floor rule is the part most often missed. If five units total 40 kW and the two largest are 15 kW and 12 kW, the 70 percent factor gives 28 kW — which is greater than 27 kW, so 28 kW governs. But if five units total 30 kW with the two largest at 12 kW each, 70 percent gives 21 kW, which is less than the 24 kW sum of the two largest, so 24 kW governs.

Restaurants — 220.88

220.88 New Restaurants. The calculated load for the service of a new restaurant may be determined from Table 220.88 , which gives demand factors by total connected load and by whether the restaurant is all-electric or not. The table's demand percentages step down as connected load rises, from 80 percent at the low end to 50 percent above 325 kVA for all-electric restaurants.

The section states that the overall calculated load shall not be less than the sum of the largest two kitchen equipment loads — the same floor rule as 220.56.

Show Windows and Track Lighting

220.43(A) Show Windows. 200 volt-amperes per linear foot , measured horizontally along the base.

220.43(B) Track Lighting. 150 volt-amperes for every 2 feet or fraction thereof of lighting track, in other than dwelling units and hotel or motel guest rooms.

220.14(F) Sign and Outline Lighting. A minimum of 1200 volt-amperes for each required branch circuit specified in 600.5(A).

  • Worked Example — Track
  • A boutique installs 27 feet of continuous lighting track. 27 ft / 2 ft = 13.5, rounded up to 14 increments
  • 14 x 150 VA = 2,100 VA
  • Motors and HVAC in the Service Calculation

220.50 Motors. Motor loads shall be calculated in accordance with 430.24, 430.25, and 430.26, and with 440.6 for air-conditioning and refrigerating equipment.

430.24 Several Motors or a Motor and Other Loads. Conductors supplying several motors, or a motor and other loads, shall have an ampacity not less than the sum of:

  • 125 percent of the full-load current rating of the highest rated motor , plus
  • the sum of the full-load current ratings of all the other motors in the group, plus

the ampacity required for the other loads.

The 125 percent applies to only one motor — the highest rated. Everything else goes in at 100 percent.

220.51 covers fixed electric space heating at 100 percent, and 220.60 permits taking only the larger of two noncoincident loads such as heating and cooling.

Existing Loads — 220.87

A very practical section for renovation work:

The calculated load of a feeder or service shall be permitted to be determined by the maximum demand data if all of the following conditions are met:

The maximum demand data is available for a 1-year period ;

The maximum demand at 125 percent plus the new load does not exceed the ampacity of the feeder or rating of the service;

The feeder has overcurrent protection in accordance with 240.4, and the service has overload protection in accordance with 230.90.

Exception: If the maximum demand data for a 1-year period is not available, the calculated load shall be permitted to be based on the maximum demand — the highest average kilowatts reached and maintained for a 15-minute interval — continuously recorded over a minimum 30-day period using a recording ammeter or power meter connected to the highest loaded phase of the feeder or service, based on the initial loading at the start of the recording. The recording shall reflect the maximum demand of the feeder or service by being taken when the building or space is occupied and shall include by measurement or calculation the larger of the heating or cooling equipment load , and other loads that may be periodic in nature due to seasonal or similar conditions.

The practical routine is: record for 30 days , multiply the recorded maximum demand by 125 percent , add the new load, and compare against the existing service rating.

Feeder Neutral and Continuous Load

Two final reminders for commercial calculations:

The grounded conductor is calculated separately under 220.61 , covered in section 8.7.

The 125 percent continuous-load multiplier applies to conductors and overcurrent devices, not to the Article 220 calculated load itself. A question that asks for "the calculated load" wants the Article 220 number; a question that asks for "the minimum conductor ampacity" wants the 125 percent version.