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8.4 The Standard Dwelling Calculation — Article 220 Part III

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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

8.4 The Standard Dwelling Calculation — Article 220 Part III

Key Takeaways Explain This Topic AI

The standard dwelling calculation adds 3 volt-amperes per square foot of general lighting, 1500 volt-amperes for each 20-ampere small-appliance circuit, and 1500 volt-amperes for the laundry circuit, then applies the Table 220.42 demand factors.

Table 220.55 Column C gives 8 kW of demand for a single household range rated 12 kW or less, increased by 5 percent for each additional kilowatt above 12 kW up to 27 kW.

NEC 220.54 requires the electric clothes dryer load to be the larger of 5000 volt-amperes or the nameplate rating, with demand factors from Table 220.54 for five or more dryers.

NEC 220.53 permits a 75 percent demand factor for four or more appliances fastened in place, other than ranges, clothes dryers, space-heating equipment, and air conditioning.

NEC 220.51 requires fixed electric space heating to be calculated at 100 percent of the total connected load, subject to the non-coincident load allowance of 220.60.

Last updated: August 2026

  • The Standard Method Step by Step 1. General lighting floor area x 3 VA/ft2
  • 2. Small appliance 1500 VA x number of circuits (minimum 2)
  • 3. Laundry 1500 VA x 1
  • 4. SUBTOTAL -> apply Table 220.42 demand factors
  • first 3000 VA at 100%
  • 3001-120,000 VA at 35%
  • 5. Fixed appliances 220.53 - 75% if four or more
  • 6. Clothes dryer 220.54 - larger of 5000 VA or nameplate
  • 7. Range / cooking 220.55 - Table demand
  • 8. Heating or A/C 220.51 at 100%, larger only per 220.60
  • 9. Motors largest motor at 125% per 220.50 / 430.24
  • 10. TOTAL VA -> divide by 240 V for a 120/240 V single-phase service
  • Step 1 through 4 — The Lighting Group

220.52(A) Small-Appliance Circuit Load. In each dwelling unit, the load shall be calculated at 1500 volt-amperes for each 2-wire small-appliance branch circuit required by 210.11(C)(1). Where the load is subdivided through two or more feeders, the calculated load for each shall include not less than 1500 volt-amperes for each 2-wire small-appliance circuit.

220.52(B) Laundry Circuit Load. A load of not less than 1500 volt-amperes shall be included for each 2-wire laundry branch circuit installed as covered in 210.11(C)(2).

220.52 also states that these loads shall be permitted to be included with the general lighting load and subjected to the demand factors provided in Table 220.42.

  • Worked Example — Lighting Group for 2,000 Square Feet General lighting 2,000 ft2 x 3 VA = 6,000 VA
  • Small appliance 2 x 1,500 VA = 3,000 VA
  • Laundry 1 x 1,500 VA = 1,500 VA
  • --------
  • Subtotal 10,500 VA

Table 220.42 demand:

  • First 3,000 VA at 100% = 3,000 VA
  • Remaining 7,500 VA at 35% = 2,625 VA
  • --------
  • Net lighting group demand 5,625 VA
  • Step 5 — Fixed Appliances, 220.53

It shall be permissible to apply a demand factor of 75 percent to the nameplate rating load of four or more appliances fastened in place , other than electric ranges, clothes dryers, space-heating equipment, or air-conditioning equipment, that are served by the same feeder or service in a one-family, two-family, or multifamily dwelling.

Count carefully. A dishwasher, disposal, water heater, and trash compactor is four appliances and qualifies for 75 percent. Three does not.

Step 6 — Clothes Dryer, 220.54

The load for household electric clothes dryers in a dwelling unit shall be either 5000 watts (volt-amperes) or the nameplate rating, whichever is larger , for each dryer served. The use of the demand factors in Table 220.54 shall be permitted.

  • Number of dryers Demand factor
  • 1–4 100 percent
  • 5 85 percent
  • 6 75 percent
  • 7 65 percent
  • 8 60 percent
  • 9 55 percent
  • 10 50 percent
  • 11 47 percent

For a single-family dwelling this reduces to: 5000 VA, or the nameplate if larger .

220.61(B)(1) later allows the feeder neutral for the dryer to be calculated at 70 percent of the ungrounded-conductor load.

Step 7 — Ranges and Cooking Appliances, 220.55

Table 220.55 gives demand loads for household electric ranges, wall-mounted ovens, counter-mounted cooking units, and other household cooking appliances over 1.75 kW rating .

Column C is used for ranges rated not over 12 kW :

  • Number of appliances Column C demand (kW)
  • 1 8
  • 2 11
  • 3 14
  • 4 17
  • 5 20
  • 6 21
  • 7 22
  • 8 23

Note 1 to Table 220.55. For ranges individually rated more than 12 kW but not more than 27 kW , and of the same rating, the maximum demand in Column C shall be increased 5 percent for each additional kilowatt of rating, or major fraction thereof, by which the rating of individual ranges exceeds 12 kW .

Note 2. For ranges individually rated more than 8.75 kW through 27 kW of unequal ratings, an average value shall be calculated by adding the ratings (using 12 kW for any range under 12 kW) and dividing by the number of ranges, then Note 1 applied.

Note 3. Over 1.75 kW through 8.75 kW, it shall be permissible to add the nameplate ratings of all household cooking appliances and multiply by the demand factors of Column A or B .

Note 4. The branch-circuit load for one range may be calculated in accordance with Table 220.55, and the branch-circuit load for one wall-mounted oven or one counter-mounted cooking unit shall be the nameplate rating.

Note 5. The neutral load for a household electric range, wall-mounted oven, or counter-mounted cooking unit shall be permitted to be 70 percent of the load determined for the ungrounded conductors.

  • Worked Example — 14 kW Range Column C for one range .................. 8 kW
  • Rating exceeds 12 kW by 2 kW
  • Increase = 2 x 5% = 10%
  • Demand = 8 kW x 1.10 = 8.8 kW = 8,800 VA
  • Neutral load (Note 5) = 8,800 x 0.70 = 6,160 VA
  • Step 8 — Heating and Air Conditioning

220.51 Fixed Electric Space Heating. Fixed electric space-heating loads shall be calculated at 100 percent of the total connected load . However, in no case shall a feeder or service load current rating be less than the rating of the largest branch circuit supplied. Exception: where reduced loading of the conductors results from units operating on duty cycle, intermittently, or from all units not operating at the same time, the authority having jurisdiction may grant permission for feeder and service conductors to have an ampacity less than 100 percent.

220.60 Non-coincident Loads allows the larger of heating and air conditioning to be used.

In Alaska the practical consequence is that dwellings with electric heat rarely benefit from 220.60, because there is usually no significant cooling load to displace. An electrically heated Alaska home carries its entire heating load at 100 percent, and that single line item often exceeds the whole rest of the calculation. This is a real design consideration and one reason many Alaska dwellings use fuel oil, natural gas, or wood as the primary heat source with electric heat only as backup.

Step 9 — Motors, 220.50

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. In practice, for a dwelling calculation this means adding 25 percent of the largest motor load to the total.

A Complete Worked Service Calculation

A 2,400-square-foot single-family dwelling in Anchorage with: two small-appliance circuits; one laundry circuit; a 12 kW range; a 5 kW clothes dryer; a 4.5 kW water heater; a 1.2 kW dishwasher; a 0.9 kW disposal; a 1.5 kW trash compactor; and 12 kW of electric baseboard heat. Calculate the service using the standard method at 120/240 V single phase. 1 General lighting 2,400 x 3 = 7,200 VA

  • 2 Small appliance 2 x 1,500 = 3,000 VA
  • 3 Laundry 1 x 1,500 = 1,500 VA
  • --------
  • Subtotal 11,700 VA
  • First 3,000 at 100% = 3,000 VA
  • Remaining 8,700 at 35% = 3,045 VA
  • Net lighting group = 6,045 VA
  • 5 Fixed appliances (4 units, 75%)
  • Water heater 4,500
  • Dishwasher 1,200
  • Disposal 900
  • Compactor 1,500
  • Sum 8,100 x 0.75 = 6,075 VA

6 Dryer larger of 5,000 or nameplate = 5,000 VA

7 Range Table 220.55 Column C, 12 kW = 8,000 VA

  • 8 Electric heat, 220.51 at 100% = 12,000 VA
  • (no A/C, so 220.60 offers no reduction)
  • --------
  • TOTAL CALCULATED LOAD 37,120 VA

Service current = 37,120 / 240 = 154.7 A

A 200-ampere service is required — the next standard size above 154.7 A that satisfies 230.79(C) and the available equipment. Under 310.12(A) , the service conductors may be sized at 83 percent of 200 A, or 166 A, which 2/0 AWG copper (175 A at 75 degrees C) satisfies.

Notice how much of the total is heat: 12,000 of 37,120 volt-amperes, nearly a third. Take the electric heat out and the calculation drops to 25,120 VA, or 104.7 A — a 125-ampere service. That single line item is what drives Alaska service sizes.

Neutral Sizing Preview

The grounded (neutral) conductor is sized separately under 220.61 , covered in section 8.7 of this chapter. The 240-volt loads — the water heater and the electric baseboard heat, if they are straight 240-volt loads with no neutral — are omitted entirely from the neutral calculation, and the range and dryer are taken at 70 percent.