All conditions and calculations are the same as for the multifamily dwelling of Example No. D4(a) served at 120/240 volts, single phase except service to each dwelling unit would be twophase legs and neutral.
Minimum Number of Branch Circuits Required for Each Dwelling Unit (See 220.11)
Range circuit: 8000 voltamperes ÷ 208 volts = 38 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)
For 120/208volt, 3wire system (without ranges) 
For 120208volt, 3wire system (with ranges) 

Minimum Size Feeders Required from Service Equipment to Meter Bank (for 20 Dwelling Units10 with Ranges)

Ranges: maximum number between any two phase legs = 4.2 x 4 = 8. Table 220.55 demand = 23,000 voltamperes 
Per phase demand: 23,000 voltamperes ÷ 2 = 11,500 voltamperes 
Equivalent 3phase load = 34,500 voltamperes 
Net calculated load (total): 40,590 voltamperes + 34,500 voltamperes = 75,090 voltamperes 
Feeder Neutral Size
Net calculated lighting and appliance load and equivalent range load
Net calculated neutral load:
Minimum Size Main Feeder (Less House Load) (for 40 Dwelling Units20 with Ranges)

Ranges: maximum number between any two phase legs = 7 
2 x 7 = 14. 
Table 220.55 demand = 29,000 voltamperes 
Per phase demand: 29,000 VA ÷ 2 = 14,500 voltamperes 
Equivalent 3phase load = 43,500 voltamperes 
Net Calculated Load (total): 69,150 voltamperes + 43,500 voltamperes = 112,650 voltamperes 
Main Feeder Neutral Size
99,600 voltamperes ÷ (208)(1.732) = 276.5 amperes
Further Demand Factor (See 220.61)
200 amperes at 100% 
200.0 A 
276.5  200 A = 76.5 amperes at 70% 
53.6 A 
Net computed load neutral 
253.6 A 