Sure raider 1. I'll copy it word-by-word.
Given:
Load A is a continuous electric discharge lighting load. The load on each ungrounded conductor of the multiwire branch circuit is 15 amperes. Because of the ballasts used, the load is considered nonlinear (neutral is current- carrying). The lampholders are not heavy duty.
Load B is a noncontinuous multioutlet receptacle load for portable appliances and tools. Each ungrounded conductor of the multiwire branch circuit supplies 10 20-ampere, 125 volt duplex receptacles. The neutral conductor carries only the unbalanced current of the conductor.
Find:
What is the rating of the overcurrent devices and what are the minimum conductor sizes?
Load A Solution:
Minimum rating of overcurrent protection protection and minimum ampacity of conductors for the continuous load [210.19.210.20]:
125 percent X 15 amperes = 18.75 - minimum 20-ampere overcurrent device and minimum 18.75-ampere ampacity.
Based on 60'C terminals the minimum conductor size is 14 American Wire Gauge (AWG) from the 60'C column [110.14(C)]. Generally, however, 14 AWG must be protected at 15 amperes, so the minimum size is 12 AWG to coordinate the conductor size with the minimum overcurrent device rating [240.4(D)].
Maximum rating of overcurrent protection: Maximum 20 amperes, based on load restrictions on higher-rated circuits [210.23].
Actual calculated load from article 220: 15-ampere load (continuous/noncontinuous adjustment is not part of Article 220 calculation).
Minimum conductor size for load:
Temperature correction factor for 75'C insulation in a 115'F ambient is 0.75.
Adjustment factor for seven current carrying-carrying conductors in the raceway is 0.70.
Adjusted ampacity = Table ampacity X 0.75 X 0.70
Minimum adjusted ampacity = 15 amperes from Article 220.
Therefore the Table ampacity X 0.75 X 0.70 must be at least equal to 15 amperes, and
Minimum table ampacity (75'C column before correction or adjustment) =
15 amperes/0.70 X 0.75 = 15 amperes/0.525 = 28.57 amperes.
Minimum conductor size based on conditions of use: 10 AWG THWN [310.15 and Table 310.16].
Overcurrent device: 20 amperes to comply with both the minimum and the maximum sizes determined above.
Conductor size: No. 10 AWG THWN, the largest of the minimum sizes determined above.
Load B Solution:
Load calculated in accordance with Article 220:
Load = 10 X 180 VA per outlet = 1800 VA [220.14(I)]
1800 VA/120 volts = 15-ampere noncontinuous load.
Minimum rating of overcurrent protection and minimum ampacity of conductors for the noncontinuous load:
100 percent X 15 A = 15 - minimum 15-ampere overcurrent device and minimum 15-ampere ampacity [210.19, 210.20].
Based on 60'C terminals, the minimum conductor size is 14 AWG from the 60'C column [110.14(C)].
Minimum overcurrent device ratings and conductor sizes for type of load:
Only 20-ampere overcurrent device may be used for 20-ampere receptacles
[210.21(B)(3)]. (This is both the maximum and minimum rating of the overcurrent device in this example.)
Because 14 AWG must generally be protected at 15 amperes, the minimum conductor size is 12 AWG to coordinate the conductor size with the 20-ampere overcurrent device rating [240.4 and 2404(D)].
Minimum conductor size for load:
THHN conductors are 90'C conductors in dry or damp locations. However, since they are associated with 75'C conductors in the same raceway, they are limited to 75'C operating temperature [310.10].
Temperature correction factor for 75'C insulation in a 115'F ambient is 0.75.
Adjustment factor for seven current-carrying conductors in the raceway is 0.70.
Adjusted ampacity = Table ampacity X 0.75 X 0.70.
Minimum adjusted ampacity = 15 amperes from Article 220.
Therefore, the Table ampacity X 0.70 X 0.75 must be at least equal to 15 amperes, and
Minimum table ampacity (75' column before adjustment or correction) =
15 amperes/0.70 X 0.75 = 15 amperes/0.525 = 28.57 amperes.
Minimum conductor size based on conditions of use: 10 AWG THHN [310.15 and Table 310.16].
Overcurrent device: 20 amperes to comply with all the minimum and maximum sizes determined above.
Conductor size: 10 AWG THHN, the largest of the minimum sizes determined above.