National Electrical Code

Chapter 2: Wiring and Protection Section 220: Branch-Circuit, Feeder, and Service Calculations ARTICLE 220 Branch-Circuit, Feeder, and Service Calculations I. General 220.1 Scope. This article provides requirements for calculating branch-circuit, feeder, and service loads. Part I provides for general requirements for calculation methods. Part II provides calculation methods for branchcircuit loads. Parts III and IV provide calculation methods for feeders and services. Part V provides calculation methods for farms. Informational Note No. 1:" See examples in Informative Annex D. Informational Note No. 2:" See Figure 220.1 for information on the organization of Article 220. Figure 220.1 Branch-Circuit, Feeder, and Service Load Calculation Methods. 220.3 Application of Other Articles. In other articles applying to the calculation of loads in specialized applications, there are requirements provided in Table 220.3 that are in addition to, or modifications of, those within this article. Table 220.3 Additional Load Calculation References Article Section (or Part) Air-conditioning and refrigerating equipment, branch-circuit conductor sizing Calculation 440 Part IV Cranes and hoists, rating and size of conductors 610 610.14 Electric vehicle charging system branchcircuit and feeder calculations 625 625.41 Electric welders, ampacity calculations 630 630.11, 630.31 Electrically driven or controlled irrigation machines Electrified truck parking space Electrolytic cell lines 675 626 668 Electroplating, branch-circuit conductor sizing Elevator feeder demand factors 675.7(A), 675.22(A) 669 620 668.3(C) 669.5 620.14 Fire pumps, voltage drop (mandatory calculation) 695 695.7 Fixed electric heating equipment for pipelines and vessels, branch-circuit sizing 427 427.4 Fixed electric space-heating equipment, branch-circuit sizing 424 424.3 Fixed outdoor electric deicing and snowmelting equipment, branch-circuit sizing 426 426.4 Industrial machinery, supply conductor sizing 670 670.4(A) Marinas and boatyards, feeder and service load calculations 555 555.12 Mobile homes, manufactured homes, and mobile home parks, total load for determining power supply 550 550.18(B) Mobile homes, manufactured homes, and mobile home parks, allowable demand factors for park electrical wiring systems 550 550.31 Motion picture and television studios and similar locations 3 sizing of feeder conductors for television studio sets 530 530.19 Motors, feeder demand factor 430 430.26 Motors, multimotor and combination-load equipment 430 430.25 Motors, several motors or a motor(s) and other load(s) 430 430.24 Over 600-volt branch-circuit calculations 210 210.19(B) Over 600-volt feeder calculations 215 215.2(B) Phase converters, conductors 455 455.6 Recreational vehicle parks, basis of calculations 551 551.73(A) Sensitive electrical equipment, voltage drop (mandatory calculation) 647 647.4(D) Solar photovoltaic systems, circuit sizing and current 690 690.8 Storage-type water heaters Theaters, stage switchboard feeders 422 520 422.11(E) 520.27 220.5 Calculations. (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. (B) Fractions of an Ampere. Calculations shall be permitted to be rounded to the nearest whole ampere, with decimal fractions smaller than 0.5 dropped. II. Branch-Circuit Load Calculations 220.10 General. Branch-circuit loads shall be calculated as shown in 220.12, 220.14, and 220.16. 220.12 Lighting Load for Specified Occupancies. A unit load of not less than that specified in Table 220.12 for occupancies specified therein shall constitute the minimum lighting load. The floor area for each floor shall be calculated from the outside dimensions of the building, dwelling unit, or other area involved. For dwelling units, the calculated floor area shall not include open porches, garages, or unused or unfinished spaces not adaptable for future use. Informational Note:" The unit values herein are based on minimum load conditions and 100 percent power factor and may not provide sufficient capacity for the installation contemplated. Exception: Where the building is designed and constructed to comply with an energy code adopted by the local authority, the lighting load shall be permitted to be calculated at the values specified in the energy code where the following conditions are met: (1) A power monitoring system is installed that will provide continuous information regarding the total general lighting load of the building. (2) The power monitoring system will be set with alarm values to alert the building owner or manager if the lighting load exceeds the values set by the energy code. (3) The demand factors specified in 220.42 are not applied to the general lighting load. Table 220.12 General Lighting Loads by Occupancy Unit Load Type of Occupancy Armories and auditoriums Volt-Amperes/ Square Meter 11 Banks Barber shops and beauty parlors 1 39b 33 11 Clubs 22 Court rooms 1 2 22 Dwelling unitsa 2 33 "6 3 "½ Hospitals 22 Hotels and motels, including apartment houses without provision for cooking by tenantsa Industrial commercial (loft) buildings 3½b 3 Churches Garages 4 commercial (storage) Volt-Amperes/ Square Foot 2 22 22 2 2 Lodge rooms 17 1½ Office buildings 39b 3½b Restaurants 22 2 Schools 33 3 Stores 33 3 Warehouses (storage) In any of the preceding occupancies except one-family dwellings and individual dwelling units of two-family and multifamily dwellings: "3 "¼ #Assembly halls and auditoriums 11 1 #Halls, corridors, closets, stairways "6 "½ #Storage spaces aSee 220.14(J). bSee 220.14(K). "3 "¼ 220.14 Other Loads — All Occupancies. In all occupancies, the minimum load for each outlet for generaluse receptacles and outlets not used for general illumination shall not be less than that calculated in 220.14(A) through (L), the loads shown being based on nominal branch-circuit voltages. Exception: The loads of outlets serving switchboards and switching frames in telephone exchanges shall be waived from the calculations. (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. (B) Electric Dryers and Electric Cooking Appliances in Dwellings and Household Cooking Appliances Used in Instructional Programs. Load calculations shall be permitted as specified in 220.54 for electric dryers and in 220.55 for electric ranges and other cooking appliances. (C) Motor Outlets. Loads for motor outlets shall be calculated in accordance with the requirements in 430.22, 430.24, and 440.6. (D) Luminaires. An outlet supplying luminaire(s) shall be calculated based on the maximum volt-ampere rating of the equipment and lamps for which the luminaire(s) is rated. (E) Heavy-Duty Lampholders. Outlets for heavy-duty lampholders shall be calculated at a minimum of 600 volt-amperes. (F) Sign and Outline Lighting. Sign and outline lighting outlets shall be calculated at a minimum of 1200 volt-amperes for each required branch circuit specified in 600.5(A). (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 (2)" At 200 volt-amperes per 300 mm (1 ft) of show window (H) Fixed Multioutlet Assemblies. Fixed multioutlet assemblies used in other than dwelling units or the guest rooms or guest suites of hotels or motels shall be calculated in accordance with (H)(1) or (H)(2). For the purposes of this section, the calculation shall be permitted to be based on the portion that contains receptacle outlets. (1)" Where appliances are unlikely to be used simultaneously, each 1.5 m (5 ft) 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. (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. This provision shall not be applicable to the receptacle outlets specified in 210.11(C)(1) and (C)(2). (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 (J)(1), (J)(2), and (J)(3) are included in the general lighting load calculations of 220.12. No additional load calculations shall be required for such outlets. (1)" All general-use receptacle outlets of 20-ampere rating or less, including receptacles connected to the circuits in 210.11(C)(3) (2)" The receptacle outlets specified in 210.52(E) and (G) (3)" The lighting outlets specified in 210.70(A) and (B) (K) Banks and Office Buildings. In banks or office buildings, the receptacle loads shall be calculated to be the larger of (1) or (2): (1)" The calculated load from 220.14(I) (2)" 11 volt-amperes/m2 or 1 volt-ampere/ft2 (L) Other Outlets. Other outlets not covered in 220.14(A) through (K) shall be calculated based on 180 voltamperes per outlet. 220.16 Loads for Additions to Existing Installations. (A) Dwelling Units. Loads added to an existing dwelling unit(s) shall comply with the following as applicable: (1)" Loads for structural additions to an existing dwelling unit or for a previously unwired portion of an existing dwelling unit, either of which exceeds 46.5 m2 (500 ft2), shall be calculated in accordance with 220.12 and 220.14. (2)" Loads for new circuits or extended circuits in previously wired dwelling units shall be calculated in accordance with either 220.12 or 220.14, as applicable. (B) Other Than Dwelling Units. Loads for new circuits or extended circuits in other than dwelling units shall be calculated in accordance with either 220.12 or 220.14, as applicable. 220.18 Maximum Loads. The total load shall not exceed the rating of the branch circuit, and it shall not exceed the maximum loads specified in 220.18(A) through (C) under the conditions specified therein. (A) Motor-Operated and Combination Loads. Where a circuit supplies only motor-operated loads, Article 430 shall apply. Where a circuit supplies only air-conditioning equipment, refrigerating equipment, or both, Article 440 shall apply. For circuits supplying loads consisting of motor-operated utilization equipment that is fastened in place and has a motor larger than 1⁄8 hp in combination with other loads, the total calculated load shall be based on 125 percent of the largest motor load plus the sum of the other loads. (B) Inductive and LED Lighting Loads. For circuits supplying lighting units that have ballasts, transformers, autotransformers, or LED drivers, the calculated load shall be based on the total ampere ratings of such units and not on the total watts of the lamps. (C) Range Loads. It shall be permissible to apply demand factors for range loads in accordance with Table 220.55, including Note 4. III. Feeder and Service Load Calculations 220.40 General. The calculated load of a feeder or service shall not be less than the sum of the loads on the branch circuits supplied, as determined by Part II of this article, after any applicable demand factors permitted by Part III or IV or required by Part V have been applied. Informational Note:" See Examples D1(a) through D10 in Informative Annex D. See 220.18(B) for the maximum load in amperes permitted for lighting units operating at less than 100 percent power factor. 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. They shall not be applied in determining the number of branch circuits for general illumination. Table 220.42 Lighting Load Demand Factors Type of Occupancy Dwelling units Portion of Lighting Load to Which Demand Factor Applies (Volt-Amperes) First 3000 or less at From 3001 to 120,000 at Demand Factor (%) 100 35 Remainder over 120,000 at Hospitals* First 50,000 or less at Remainder over 50,000 at Hotels and motels, including apartment houses without provision for cooking by tenants* Warehouses (storage) 20 First 20,000 or less at 50 From 20,001 to 100,000 at 40 Remainder over 100,000 at First 12,500 or less at Remainder over 12,500 at All others 25 40 Total volt-amperes 30 100 50 100 *The demand factors of this table shall not apply to the calculated load of feeders or services supplying areas in hospitals, hotels, and motels where the entire lighting is likely to be used at one time, as in operating rooms, ballrooms, or dining rooms. 220.43 Show-Window and Track Lighting. (A) Show Windows. For show-window lighting, a load of not less than 660 volt-amperes/linear meter or 200 volt-amperes/linear foot shall be included for a show window, measured horizontally along its base. Informational Note:" See 220.14(G) for branch circuits supplying show windows. (B) Track Lighting. For track lighting in other than dwelling units or guest rooms or guest suites of hotels or motels, an additional load of 150 volt-amperes shall be included for every 600 mm (2 ft) of lighting track or fraction thereof. Where multicircuit track is installed, the load shall be considered to be divided equally between the track circuits. Exception: If the track lighting is supplied through a device that limits the current to the track, the load shall be permitted to be calculated based on the rating of the device used to limit the current. 220.44 Receptacle Loads — Other Than Dwelling Units. Receptacle loads calculated in accordance with 220.14(H) and (I) shall be permitted to be made subject to the demand factors given in Table 220.42 or Table 220.44. Table 220.44 Demand Factors for Non-Dwelling Receptacle Loads Portion of Receptacle Load to Which Demand Factor Applies (VoltAmperes) Demand Factor (%) First 10 kVA or less at 100 Remainder over 10 kVA at 50 220.50 Motors. Motor loads shall be calculated in accordance with 430.24, 430.25, and 430.26 and with 440.6 for hermetic refrigerant motor compressors. 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, provided the conductors have an ampacity for the load so determined. 220.52 Small-Appliance and Laundry Loads — Dwelling Unit. (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 as covered 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 branch circuit. These loads shall be permitted to be included with the general lighting load and subjected to the demand factors provided in Table 220.42. Exception: The individual branch circuit permitted by 210.52(B)(1), Exception No. 2, shall be permitted to be excluded from the calculation required by 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 by 210.11(C)(2). This load shall be permitted to be included with the general lighting load and subjected to the demand factors provided in Table 220.42. 220.53 Appliance Load — Dwelling Unit(s). 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. 220.54 Electric Clothes Dryers — Dwelling Unit(s). The load for household electric clothes dryers in a dwelling unit(s) 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. Where two or more single-phase dryers are supplied by a 3-phase, 4-wire feeder or service, the total load shall be calculated on the basis of twice the maximum number connected between any two phases. Kilovolt-amperes (kVA) shall be considered equivalent to kilowatts (kW) for loads calculated in this section. Table 220.54 Demand Factors for Household Electric Clothes Dryers Number of Dryers Demand Factor (%) 134 100 5 85 6 75 7 65 8 60 9 55 10 50 11 47 12323 47% minus 1% for each dryer exceeding 11 24342 35% minus 0.5% for each dryer exceeding 23 43 and over 25% 220.55 Electric Cooking Appliances in Dwelling Units and Household Cooking Appliances Used in Instructional Programs. The load for household electric ranges, wall-mounted ovens, counter-mounted cooking units, and other household cooking appliances individually rated in excess of 1¾ kW shall be permitted to be calculated in accordance with Table 220.55. Kilovolt-amperes (kVA) shall be considered equivalent to kilowatts (kW) for loads calculated under this section. Where two or more single-phase ranges are supplied by a 3-phase, 4-wire feeder or service, the total load shall be calculated on the basis of twice the maximum number connected between any two phases. Table 220.55 Demand Factors and Loads for Household Electric Ranges, Wall-Mounted Ovens, CounterMounted Cooking Units, and Other Household Cooking Appliances over 1¾ kW Rating (Column C to be used in all cases except as otherwise permitted in Note 3.) Demand Factor (%) (See Notes) Number of Appliances Column A (Less than 3½ kW Rating) Column B (3½ kW through 8¾ kW Rating) Column C Maximum Demand (kW) (See Notes) (Not over 12 kW Rating) 1 80 80 8 2 75 65 11 3 70 55 14 4 66 50 17 5 62 45 20 6 59 43 21 7 56 40 22 8 53 36 23 9 51 35 24 10 49 34 25 11 47 32 26 12 45 32 27 13 43 32 28 14 41 32 29 15 40 32 30 16 39 28 31 17 38 28 32 18 37 28 33 19 36 28 34 20 35 28 35 21 34 26 36 22 33 26 37 23 32 26 38 24 31 26 39 25 30 26 26330 30 24 31340 30 22 41350 30 20 51360 30 18 61 and over 30 40 15 kW + 1 kW for each range 25 kW + ¾ kW for each range 16 Notes: 1. Over 12 kW through 27 kW ranges all of same rating. For ranges individually rated more than 12 kW but not more than 27 kW, 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. 2. Over 8¾ kW through 27 kW ranges of unequal ratings. For ranges individually rated more than 8¾ kW and of different ratings, but none exceeding 27 kW, an average value of rating shall be calculated by adding together the ratings of all ranges to obtain the total connected load (using 12 kW for any range rated less than 12 kW) and dividing by the total number of ranges. Then the maximum demand in Column C shall be increased 5 percent for each kilowatt or major fraction thereof by which this average value exceeds 12 kW. 3. Over 1¾ kW through 8¾ kW. In lieu of the method provided in Column C, it shall be permissible to add the nameplate ratings of all household cooking appliances rated more than 1¾ kW but not more than 8¾ kW and multiply the sum by the demand factors specified in Column A or Column B for the given number of appliances. Where the rating of cooking appliances falls under both Column A and Column B, the demand factors for each column shall be applied to the appliances for that column, and the results added together. 4. Branch-Circuit Load. It shall be permissible to calculate the branch-circuit load for one range in accordance with Table 220.55. The branch-circuit load for one wall-mounted oven or one counter-mounted cooking unit shall be the nameplate rating of the appliance. The branch-circuit load for a counter-mounted cooking unit and not more than two wall-mounted ovens, all supplied from a single branch circuit and located in the same room, shall be calculated by adding the nameplate rating of the individual appliances and treating this total as equivalent to one range. 5. This table shall also apply to household cooking appliances rated over 1¾ kW and used in instructional programs. Informational Note No. 1:" See the examples in Informative Annex D. Informational Note No. 2:" See Table 220.56 for commercial cooking equipment. • 220.56 Kitchen Equipment — Other Than Dwelling Unit(s). 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. Table 220.56 Demand Factors for Kitchen Equipment — Other Than Dwelling Unit(s) Number of Units of Equipment Demand Factor (%) 1 100 2 100 3 90 4 80 5 6 and over 70 65 220.60 Noncoincident Loads. 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(s) that will be used at one time for calculating the total load of a feeder or service. 220.61 Feeder or Service Neutral Load. (A) Basic Calculation. The feeder or service neutral load shall be the maximum unbalance of the load determined by this article. The maximum unbalanced load shall be the maximum net calculated load between the neutral conductor and any one ungrounded conductor. Exception: For 3-wire, 2-phase or 5-wire, 2-phase systems, the maximum unbalanced load shall be the maximum net calculated load between the neutral conductor and any one ungrounded conductor multiplied by 140 percent. (B) Permitted Reductions. A service or feeder supplying the following loads shall be permitted to have an additional demand factor of 70 percent applied to the amount in 220.61(B)(1) or portion of the amount in 220.61(B)(2) determined by the basic calculation: (1)" (2)" A feeder or service supplying household electric ranges, wall-mounted ovens, counter-mounted cooking units, and electric dryers, where the maximum unbalanced load has been determined in accordance with Table 220.55 for ranges and Table 220.54 for dryers That portion of the unbalanced load in excess of 200 amperes where the feeder or service is supplied from a 3-wire dc or single-phase ac system; or a 4-wire, 3-phase, 3-wire, 2-phase system; or a 5-wire, 2phase system Informational Note:" See Examples D1(a), D1(b), D2(b), D4(a), and D5(a) in Informative Annex D. (C) Prohibited Reductions. There shall be no reduction of the neutral or grounded conductor capacity applied to the amount in 220.61(C)(1), or portion of the amount in (C)(2), from that determined by the basic calculation: (1)" Any portion of a 3-wire circuit consisting of 2 ungrounded conductors and the neutral conductor of a 4wire, 3-phase, wye-connected system (2)" That portion consisting of nonlinear loads supplied from a 4-wire, wye-connected, 3-phase system • Informational Note:" A 3-phase, 4-wire, wye-connected power system used to supply power to nonlinear loads may necessitate that the power system design allow for the possibility of high harmonic neutral conductor currents. IV. Optional Feeder and Service Load Calculations 220.80 General. Optional feeder and service load calculations shall be permitted in accordance with Part IV. 220.82 Dwelling Unit. (A) Feeder and Service Load. This section applies to a dwelling unit having the total connected load served by a single 120/240-volt or 208Y/120-volt set of 3-wire service or feeder conductors with an ampacity of 100 or greater. It shall be permissible to calculate the feeder and service loads in accordance with this section instead of the method specified in Part III of this article. The calculated load shall be the result of adding the loads from 220.82(B) and (C). Feeder and service-entrance conductors whose calculated load is determined by this optional calculation shall be permitted to have the neutral load determined by 220.61. (B) General Loads. The general calculated load shall be not less than 100 percent of the first 10 kVA plus 40 percent of the remainder of the following loads: (1)" 33 volt-amperes/m2 or 3 volt-amperes/ft2 for general lighting and general-use receptacles. The floor area for each floor shall be calculated from the outside dimensions of the dwelling unit. The calculated floor area shall not include open porches, garages, or unused or unfinished spaces not adaptable for future use. (2)" 1500 volt-amperes for each 2-wire, 20-ampere small-appliance branch circuit and each laundry branch circuit covered in 210.11(C)(1) and (C)(2). (3)" The nameplate rating of the following: (4)" a." All appliances that are fastened in place, permanently connected, or located to be on a specific circuit b." Ranges, wall-mounted ovens, counter-mounted cooking units c." Clothes dryers that are not connected to the laundry branch circuit specified in item (2) d." Water heaters The nameplate ampere or kVA rating of all permanently connected motors not included in item (3). (C) Heating and Air-Conditioning Load. The largest of the following six selections (load in kVA) shall be included: (1)" 100 percent of the nameplate rating(s) of the air conditioning and cooling. (2)" 100 percent of the nameplate rating(s) of the heat pump when the heat pump is used without any supplemental electric heating. (3)" 100 percent of the nameplate rating(s) of the heat pump compressor and 65 percent of the supplemental electric heating for central electric space-heating systems. If the heat pump compressor is prevented from operating at the same time as the supplementary heat, it does not need to be added to the supplementary heat for the total central space heating load. (4)" 65 percent of the nameplate rating(s) of electric space heating if less than four separately controlled units. (5)" 40 percent of the nameplate rating(s) of electric space heating if four or more separately controlled units. (6)" 100 percent of the nameplate ratings of electric thermal storage and other heating systems where the usual load is expected to be continuous at the full nameplate value. Systems qualifying under this selection shall not be calculated under any other selection in 220.82(C). 220.83 Existing Dwelling Unit. This section shall be permitted to be used to determine if the existing service or feeder is of sufficient capacity to serve additional loads. Where the dwelling unit is served by a 120/240volt or 208Y/120-volt, 3-wire service, it shall be permissible to calculate the total load in accordance with 220.83(A) or (B). (A) Where Additional Air-Conditioning Equipment or Electric Space-Heating Equipment Is Not to Be Installed. The following percentages shall be used for existing and additional new loads. Load (kVA) Percent of Load First 8 kVA of load at 100 Remainder of load at 40 Load calculations shall include the following: (1)" General lighting and general-use receptacles at 33 volt-amperes/m2 or 3 volt-amperes/ft2 as determined by 220.12 (2)" 1500 volt-amperes for each 2-wire, 20-ampere small-appliance branch circuit and each laundry branch circuit covered in 210.11(C)(1) and (C)(2) (3)" The nameplate rating of the following: a." All appliances that are fastened in place, permanently connected, or located to be on a specific circuit b." Ranges, wall-mounted ovens, counter-mounted cooking units c." Clothes dryers that are not connected to the laundry branch circuit specified in item (2) d." Water heaters (B) Where Additional Air-Conditioning Equipment or Electric Space-Heating Equipment Is to Be Installed. The following percentages shall be used for existing and additional new loads. The larger connected load of air-conditioning or space-heating, but not both, shall be used. Load Percent of Load Air-conditioning equipment 100 Central electric space heating 100 Less than four separately controlled space-heating units 100 First 8 kVA of all other loads 100 Remainder of all other loads 40 Other loads shall include the following: (1)" General lighting and general-use receptacles at 33 volt-amperes/m2 or 3 volt-amperes/ft2 as determined by 220.12 (2)" 1500 volt-amperes for each 2-wire, 20-ampere small-appliance branch circuit and each laundry branch circuit covered in 210.11(C)(1) and (C)(2) (3)" The nameplate rating of the following: a." All appliances that are fastened in place, permanently connected, or located to be on a specific circuit b." Ranges, wall-mounted ovens, counter-mounted cooking units c." Clothes dryers that are not connected to the laundry branch circuit specified in (2) d." Water heaters 220.84 Multifamily Dwelling. (A) Feeder or Service Load. It shall be permissible to calculate the load of a feeder or service that supplies three or more dwelling units of a multifamily dwelling in accordance with Table 220.84 instead of Part III of this article if all the following conditions are met: (1)" (2)" No dwelling unit is supplied by more than one feeder. Each dwelling unit is equipped with electric cooking equipment. Exception: When the calculated load for multifamily dwellings without electric cooking in Part III of this article exceeds that calculated under Part IV for the identical load plus electric cooking (based on 8 kW per unit), the lesser of the two loads shall be permitted to be used. (3)" Each dwelling unit is equipped with either electric space heating or air conditioning, or both. Feeders and service conductors whose calculated load is determined by this optional calculation shall be permitted to have the neutral load determined by 220.61. (B) House Loads. House loads shall be calculated in accordance with Part III of this article and shall be in addition to the dwelling unit loads calculated in accordance with Table 220.84. Table 220.84 Optional Calculations — Demand Factors for Three or More Multifamily Dwelling Units Number of Dwelling Units 335 Demand Factor (%) 45 637 44 8310 43 11 42 12313 41 14315 40 16317 39 18320 38 21 37 22323 36 24325 35 26327 34 28330 33 31 32 32333 31 34336 30 37338 29 39342 28 43345 27 46350 26 51355 25 56361 24 62 and over 23 (C) Calculated Loads. The calculated load to which the demand factors of Table 220.84 apply shall include the following: (1)" 33 volt-amperes/m2 or 3 volt-amperes/ft2 for general lighting and general-use receptacles (2)" 1500 volt-amperes for each 2-wire, 20-ampere small-appliance branch circuit and each laundry branch circuit covered in 210.11(C)(1) and (C)(2) (3)" The nameplate rating of the following: a." All appliances that are fastened in place, permanently connected, or located to be on a specific circuit b." Ranges, wall-mounted ovens, counter-mounted cooking units c." Clothes dryers that are not connected to the laundry branch circuit specified in item (2) d." Water heaters (4)" The nameplate ampere or kVA rating of all permanently connected motors not included in item (3) (5)" The larger of the air-conditioning load or the fixed electric space-heating load 220.85 Two Dwelling Units. Where two dwelling units are supplied by a single feeder and the calculated load under Part III of this article exceeds that for three identical units calculated under 220.84, the lesser of the two loads shall be permitted to be used. 220.86 Schools. The calculation of a feeder or service load for schools shall be permitted in accordance with Table 220.86 in lieu of Part III of this article where equipped with electric space heating, air conditioning, or both. The connected load to which the demand factors of Table 220.86 apply shall include all of the interior and exterior lighting, power, water heating, cooking, other loads, and the larger of the air-conditioning load or space-heating load within the building or structure. Feeders and service conductors whose calculated load is determined by this optional calculation shall be permitted to have the neutral load determined by 220.61. Where the building or structure load is calculated by this optional method, feeders within the building or structure shall have ampacity as permitted in Part III of this article; however, the ampacity of an individual feeder shall not be required to be larger than the ampacity for the entire building. This section shall not apply to portable classroom buildings. Table 220.86 Optional Method — Demand Factors for Feeders and Service Conductors for Schools Connected Load First 33 VA/m2 Plus, (3 VA/ft2) at Over 33 through 220 VA/m2 Plus, (3 through 20 VA/ft2) at Remainder over 220 VA/m2 (20 VA/ft2) at Demand Factor (Percent) 100 75 25 220.87 Determining Existing Loads. The calculation of a feeder or service load for existing installations shall be permitted to use actual maximum demand to determine the existing load under all of the following conditions: (1)" The maximum demand data is available for a 1-year period. 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 (measure of average power demand over a 15minute period) 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. (2)" The maximum demand at 125 percent plus the new load does not exceed the ampacity of the feeder or rating of the service. (3)" The feeder has overcurrent protection in accordance with 240.4, and the service has overload protection in accordance with 230.90. 220.88 New Restaurants. Calculation of a service or feeder load, where the feeder serves the total load, for a new restaurant shall be permitted in accordance with Table 220.88 in lieu of Part III of this article. The overload protection of the service conductors shall be in accordance with 230.90 and 240.4. Feeder conductors shall not be required to be of greater ampacity than the service conductors. Service or feeder conductors whose calculated load is determined by this optional calculation shall be permitted to have the neutral load determined by 220.61. Table 220.88 Optional Method — Permitted Load Calculations for Service and Feeder Conductors for New Restaurants Total Connected Load (kVA) All Electric Restaurant Calculated Loads (kVA) ""03200 Not All Electric Restaurant Calculated Loads (kVA) 80% 100% 2013325 10% (amount over 200) + 160.0 "50% (amount over 200) + 200.0 3263800 50% (amount over 325) + 172.5 "45% (amount over 325) + 262.5 Over 800 50% (amount over 800) + 410.0 "20% (amount over 800) + 476.3 Note: Add all electrical loads, including both heating and cooling loads, to calculate the total connected load. Select the one demand factor that applies from the table, then multiply the total connected load by this single demand factor. V. Farm Load Calculations 220.100 General. Farm loads shall be calculated in accordance with Part V. 220.102 Farm Loads — Buildings and Other Loads. (A) Dwelling Unit. The feeder or service load of a farm dwelling unit shall be calculated in accordance with the provisions for dwellings in Part III or IV of this article. Where the dwelling has electric heat and the farm has electric grain-drying systems, Part IV of this article shall not be used to calculate the dwelling load where the dwelling and farm loads are supplied by a common service. (B) Other Than Dwelling Unit. Where a feeder or service supplies a farm building or other load having two or more separate branch circuits, the load for feeders, service conductors, and service equipment shall be calculated in accordance with demand factors not less than indicated in Table 220.102. Table 220.102 Method for Calculating Farm Loads for Other Than Dwelling Unit Ampere Load at 240 Volts Maximum Demand Factor (%) The greater of the following: #All loads that are expected to operate simultaneously, or 100 #125 percent of the full load current of the largest motor, or #First 60 amperes of the load Next 60 amperes of all other loads 50 Remainder of other loads 25 220.103 Farm Loads — Total. Where supplied by a common service, the total load of the farm for service conductors and service equipment shall be calculated in accordance with the farm dwelling unit load and demand factors specified in Table 220.103. Where there is equipment in two or more farm equipment buildings or for loads having the same function, such loads shall be calculated in accordance with Table 220.102 and shall be permitted to be combined as a single load in Table 220.103 for calculating the total load. Table 220.103 Method for Calculating Total Farm Load Individual Loads Calculated in Accordance with Table 220.102 Demand Factor (%) Largest load 100 Second largest load 75 Third largest load 65 Remaining loads 50 Note: To this total load, add the load of the farm dwelling unit calculated in accordance with Part III or IV of this article. Where the dwelling has electric heat and the farm has electric grain-drying systems, Part IV of this article shall not be used to calculate the dwelling load.