8.3 Article 220 Part II: General Lighting, Receptacles and Demand Factors
Key Takeaways
- Table 220.12 assigns a general lighting load of 3 volt-amperes per square foot for dwelling units, computed from the outside dimensions and excluding open porches, garages, and unused spaces not adaptable for future use.
- NEC 220.14(I) assigns 180 volt-amperes to each single or multiple receptacle on one yoke, and 90 volt-amperes per receptacle for an assembly of four or more receptacles.
- Table 220.42 applies dwelling lighting demand factors of 100 percent to the first 3000 volt-amperes, 35 percent from 3001 to 120,000 volt-amperes, and 25 percent above that.
- Table 220.44 applies non-dwelling receptacle demand factors of 100 percent to the first 10 kVA and 50 percent to the remainder.
- NEC 220.14(J) states that in dwelling occupancies no additional load calculation is required for general-use receptacle outlets and lighting outlets, because they are included in the 3 volt-amperes per square foot general lighting load.
The Structure of Article 220
| Part | Covers |
|---|---|
| I | General — scope, calculations, and rounding |
| II | Branch-Circuit Load Calculations — the building blocks |
| III | Feeder and Service Load Calculations — the standard method |
| IV | Optional Feeder and Service Load Calculations — 220.82 through 220.88 |
| V | Farm Load Calculations |
220.5(A) Voltages. Unless other voltages are specified, for purposes of calculating branch-circuit and feeder loads, nominal system voltages of 120, 120/240, 208Y/120, 240, 347, 480Y/277, 480, 600Y/347, and 600 volts shall be used.
220.5(B) Fractions of an Ampere. Where calculations result in a fraction of an ampere that is less than 0.5, such fractions shall be permitted to be dropped. So 47.4 A may be treated as 47 A, but 47.6 A rounds up to 48 A.
General Lighting Load — 220.12 and Table 220.12
220.12 General Lighting. A unit load of not less than that specified in Table 220.12 for occupancies specified shall constitute the minimum lighting load. The floor area shall be computed from the outside dimensions of the building, dwelling unit, or other area involved. For dwelling units, the computed floor area shall not include open porches, garages, or unused or unfinished spaces not adaptable for future use.
Selected values from Table 220.12:
| Occupancy | VA per square foot |
|---|---|
| Dwelling units | 3 |
| Hotels and motels, including apartment houses without provision for cooking by tenants | 2 |
| Hospitals | 2 |
| Schools | 3 |
| Stores | 3 |
| Office buildings | 3.5 |
| Banks | 3.5 |
| Restaurants | 2 |
| Industrial commercial (loft) buildings | 2 |
| Warehouses (storage) | 0.25 |
| Garages — commercial (storage) | 0.5 |
| Armories and auditoriums | 1 |
| Churches | 1 |
| Lodge rooms | 1.5 |
| Clubs | 2 |
| Court rooms | 2 |
For banks and office buildings, an additional receptacle load is added where the number of general-purpose receptacle outlets is unknown: 1 volt-ampere per square foot under 220.14(K).
Other Loads — 220.14
220.14(A) Specific Appliances or Loads. An outlet for a specific appliance or other load not covered in 220.14(B) through (L) shall be calculated based on the ampere rating of the appliance or load served.
220.14(C) Motor Loads. Outlets for motor loads shall be calculated in accordance with the requirements in 430.22, 430.24, and 440.6.
220.14(D) Luminaires. An outlet supplying luminaires shall be calculated based on the maximum volt-ampere rating of the equipment and lamps for which the luminaire is rated.
220.14(E) Heavy-Duty Lampholders. Outlets for heavy-duty lampholders shall be calculated at a minimum of 600 volt-amperes.
220.14(F) Sign and Outline Lighting. Sign and outline lighting outlets required by 600.5(A) shall be calculated at a minimum of 1200 volt-amperes for each required branch circuit.
220.14(G) Show Windows. Show windows shall be calculated in accordance with either of the following: (1) the unit load per outlet as required in other provisions of this section; or (2) at 200 volt-amperes per 300 mm (linear foot) of show window.
220.14(H) Fixed Multioutlet Assemblies. In other than dwelling units or the guest rooms or guest suites of hotels or motels, fixed multioutlet assemblies shall be calculated as follows: (1) where appliances are unlikely to be used simultaneously, each 5 feet or fraction thereof of each separate and continuous length shall be considered as one outlet of not less than 180 volt-amperes; (2) where appliances are likely to be used simultaneously, each 300 mm (1 ft) or fraction thereof shall be considered as an outlet of not less than 180 volt-amperes.
220.14(I) Receptacle Outlets. Except as covered in 220.14(J) and (K), receptacle outlets shall be calculated at not less than 180 volt-amperes for each single or for each multiple receptacle on one yoke. A single piece of equipment consisting of a multiple receptacle comprised of four or more receptacles shall be calculated at not less than 90 volt-amperes per receptacle.
So a duplex receptacle is 180 VA, not 360. A quad receptacle on two yokes is 360 VA; a listed four-receptacle assembly on one yoke is 4 x 90 = 360 VA.
220.14(J) Dwelling Occupancies. In one-family, two-family, and multifamily dwellings and in guest rooms or guest suites of hotels and motels, the outlets specified in (1), (2), and (3) are included in the general lighting load calculations of 220.12. No additional load calculations shall be required for such outlets:
- All general-use receptacle outlets of 20-ampere rating or less, including receptacles connected to the circuits in 210.11(C)(3);
- The receptacle outlets specified in 210.52(E) and (G);
- The lighting outlets specified in 210.70(A) and (B).
This is a critical simplification: in a dwelling you do not count receptacles individually. The 3 VA per square foot covers them all.
220.14(K) Banks and Office Buildings. In banks or office buildings, the receptacle loads shall be calculated to be the larger of: (1) the calculated load from 220.14(I) after applying the demand factors in Table 220.44; or (2) 1 volt-ampere per square foot.
220.14(L) Other Outlets. Other outlets not covered in (A) through (K) shall be calculated based on 180 volt-amperes per outlet.
Track Lighting — 220.43(B)
For track lighting in other than dwelling units or the guest rooms or guest suites of hotels or motels, an additional load of 150 volt-amperes shall be included for every 2 feet of lighting track or fraction thereof. Where multicircuit track is installed, the load shall be considered to be divided equally between the track circuits.
A 17-foot run of track: 17 divided by 2 = 8.5, rounded up to 9 two-foot increments, times 150 VA = 1350 VA.
Show Windows — 220.43(A)
For show-window lighting, a load of not less than 200 volt-amperes shall be included for each linear foot of show window, measured horizontally along its base.
210.62 separately requires at least one receptacle outlet for each 12 linear feet or major fraction thereof of show window area.
Demand Factors — Table 220.42
220.42 General Lighting. The demand factors specified in Table 220.42 shall apply to that portion of the total branch-circuit load calculated for general illumination:
| Type of occupancy | Portion of lighting load (VA) | Demand factor |
|---|---|---|
| Dwelling units | First 3000 | 100 percent |
| 3001 to 120,000 | 35 percent | |
| Remainder over 120,000 | 25 percent | |
| Hospitals | First 50,000 | 40 percent |
| Remainder | 20 percent | |
| Hotels and motels, including apartment houses without provision for cooking by tenants | First 20,000 | 50 percent |
| 20,001 to 100,000 | 40 percent | |
| Remainder | 30 percent | |
| Warehouses (storage) | First 12,500 | 100 percent |
| Remainder | 50 percent | |
| All others | Total volt-amperes | 100 percent |
Note the footnote to the hospital and hotel rows: the demand factors shall not apply to the calculated load for feeders or services supplying areas in hospitals, hotels, and motels where the entire lighting is likely to be used at one time, such as in operating rooms, ballrooms, or dining rooms.
Receptacle Demand Factors — Table 220.44
220.44 Receptacle Loads — Other Than Dwelling Units. Receptacle loads calculated at not more than 180 volt-amperes per outlet in accordance with 220.14(I) and (L) shall be permitted to be made subject to the demand factors in Table 220.42 or Table 220.44:
| Portion of receptacle load | Demand factor |
|---|---|
| First 10 kVA or less | 100 percent |
| Remainder over 10 kVA | 50 percent |
Worked Example — Office Receptacles
An office has 70 duplex general-use receptacles on single yokes. What is the calculated demand load?
Connected load = 70 x 180 VA = 12,600 VA
First 10,000 VA at 100% = 10,000 VA
Remaining 2,600 VA at 50% = 1,300 VA
----------
Calculated demand = 11,300 VA
In an office building, 220.14(K) then requires comparing this against 1 VA per square foot and taking the larger of the two.
Non-Coincident Loads — 220.60
Where it is unlikely that two or more noncoincident loads will be in use simultaneously, it shall be permissible to use only the largest load that will be used at one time for calculating the total load of a feeder or service.
The standard application is heating versus air conditioning. A dwelling with 8.0 kW of electric heat and 5.0 kW of air conditioning includes only the 8.0 kW, because they never run at the same time. In Alaska this reduction rarely helps, since a dwelling with electric heat and no cooling has nothing to omit — the heating load stands alone at 100 percent under 220.51.
Continuous Loads — 220.10 and 215.2
The 125 percent continuous-load multiplier is applied in the feeder and service calculation, not inside Article 220 Part II. Keep the two steps distinct: Part II establishes the connected load, and 210.19/210.20/215.2/215.3/230.42 apply the continuous-load multiplier when sizing conductors and overcurrent devices.
A dwelling unit measures 2,400 square feet of habitable area computed from outside dimensions. What is the general lighting load under Table 220.12?
How many volt-amperes are assigned to a duplex receptacle outlet on a single yoke in a commercial occupancy under NEC 220.14(I)?
A retail store installs 25 linear feet of show window. What minimum load must be included under NEC 220.43(A)?
Why does a dwelling-unit load calculation not add 180 volt-amperes for each general-use receptacle?