luckyboy886
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Per NEC Section 220.61, the feeder or service neutral load shall be the maximum unbalance of the load between the neutral conductor and any one ungrounded conductor.
When I reviewed examples D1(a)/(B), D2(a)/(B) in Annex D, I was confused which appliance loads should be included on the neutral load for Dwelling feeder and service. However, I observed the following from these examples:
1) If the appliance voltage rating is 115V or 120V, it needs to be included in the neutral load calculation. (unbalanced load)
2) If the appliance voltage rating is 230V or 240v, it doesn't need to be included in the neutral load calc. (balanced load)
3) If the appliance voltage rating is not given, use common sense to justify whether the appliance voltage is 120V or 240V, then determine whether it should be included in the neutral load calcuation. (That's why A/C unit, space heating, and water heater are not considered for the neutral load calc in examples D2(a) and D2(B).)
The above is based on my own observation. Can anyone have a better idea how to determine the neutral load calcuation.
To extend further, how to size the neutral conductor? Use Table 310.15(B)(16) or something else?
Thanks!
When I reviewed examples D1(a)/(B), D2(a)/(B) in Annex D, I was confused which appliance loads should be included on the neutral load for Dwelling feeder and service. However, I observed the following from these examples:
1) If the appliance voltage rating is 115V or 120V, it needs to be included in the neutral load calculation. (unbalanced load)
2) If the appliance voltage rating is 230V or 240v, it doesn't need to be included in the neutral load calc. (balanced load)
3) If the appliance voltage rating is not given, use common sense to justify whether the appliance voltage is 120V or 240V, then determine whether it should be included in the neutral load calcuation. (That's why A/C unit, space heating, and water heater are not considered for the neutral load calc in examples D2(a) and D2(B).)
The above is based on my own observation. Can anyone have a better idea how to determine the neutral load calcuation.
To extend further, how to size the neutral conductor? Use Table 310.15(B)(16) or something else?
Thanks!
