A multifamily dwelling has 40 dwelling units.
Meters in two banks of 20 each and individual feeders to each dwelling unit.
Onehalf of the dwelling units are equipped with electric ranges not exceeding 12 kW each. Assume range kW rating equivalent to kVA rating in accordance with 220.55. Other half of ranges are gas ranges.
Area of each dwelling unit is 840 square feet.
Laundry facilities on premises are available to all tenants. Add no circuit to individual dwelling unit.
Calculated Load for Each Dwelling Unit (See Article 220)
General lighting: 840 sq. ft. at 3 voltamperes per sq. ft. 
2520 VA 
Special appliance load: electric range (see 250.55) 
8000 VA 
Minimum Number of Branch Circuits Required for Each Dwelling Unit [See 210.11(A)]:
General lighting load: 2520 voltamperes ÷ 120 V = 21 amperes or two 15ampere, 2wire circuits; or two 20ampere, 2wire circuits.
Small appliance load: Two 2wire circuits of 12 AWG wire [see 220.11(C)(1)].
Range circuit: 8000 voltamperes ÷ 240 volts = 33 amperes or a circuit of two 8 AWG conductors and one 10 AWG conductor as per 210.19(A)(3).
Minimum Size Feeder Required for Each Dwelling Unit (See 215.2)
Calculated load (Article 220) 


2520 VA 

3000 VA 

5520 VA 
Application of Demand Factor (see Table 220.42)
First 3000 voltamperes at 100% 
3000 VA 
5520 VA  3000 VA = 2520 voltamperes at 35% 
882 VA 

3882 VA 
Range load 
8000 VA 

11,882 VA 
Size of Each Feeder (See 215.2)
For 120/240volt, 3wire system (without ranges): 

= 16.2 A 

For 120/240volt, 3wire system (with ranges): 

= 49.5 A 
Feeder Neutral
Lighting and small appliance 
3882 VA 
Range: 8000 voltamperes at 70% (see Section 220.61) (only for apart ments with electric ranges) 
5600 VA 

9482 VA 
Calculated Load for Neutral
9482 VA ÷ 240 V = 39.5 A
Minimum Size Feeders Required from Service Equipment to Meter Bank (for 20 Dwelling Units10 with Ranges)
Total calculated load: 


110,400 VA 
Application of Demand Factor: 


3000 VA 

37,950 VA 

40,590 VA 

25,000 VA 

65,590 VA 
Net calculated load for 120/240volt, 3wire system:
Feeder Neutral
Lighting and small appliance 
40,590 VA 
Range: 25,000 voltamperes at 70% [see 220.61(B)] 
17,500 VA 

58,090 VA 
Calculated Load for Neutral
Further Demand Factor [220.61(B)]:
200 amperes at 100% 
200 A 
242A  200 A = 42 amperes at 70% 
29 A 

229 A 
Minimum Size Main Feeder (or Service Conductors) Required (Less House Load) (for 40 Dwelling Units20 with Ranges)
Total calculated load: 


220,800 VA 
Application of Demand Factor (from Table 220.42)
First 3000 voltamperes at 100% 
3000 VA 
Next 120,000 VA  3000 VA = 117,000 voltamperes at 35% 
40,950 VA 
Remainder 220,800 VA  120,000 VA = 100,800 voltamperes at 25% 
25,200 VA 

69,150 VA 
Range load, 20 ranges (less than 12 kVA) (see Col. C, Table 220.55) 
35,000 VA 

104,150 VA 


Feeder Neutral
Lighting and small appliance load 
69,150 VA 
Range load, 35,000 voltamperes at 70% [see 220.61(B)] 
24,500 VA 

93,650 VA 
Further Demand Factor [See 220.61(B)]
200 amperes at 100% 
200 A 
390A  200 A = 190 amperes at 70% 
133 A 

333 A 
[See Tables Table 310.16 through 310.21 and 310.15(B)(2) and (B)(4).]
Article 90 Introduction
General
Wiring and Protection
Wiring Methods and Materials
Equipment for General Use
Special Occupancies
Special Equipment
Special Conditions
Tables
Annex C. Conduit and Tubing Fill Tables for Conductors and Fixture Wires of the Same Size
Annex D. Examples
Annex E. Types of Construction