Part III of NEC Art. 220 provides requirements for the calculated load of specific applications (after covering general loads and general lighting). Do you know the types of loads that are covered here?
They include:
- Show window and track lighting
- Receptacle loads other than dwelling units
- Motors
- Fixed electric space heating
- Small appliance and laundry loads (dwelling unit)
- Electric cooking appliances
- Kitchen equipment (other than dwelling units)
Then, it talks about noncoincident loads. These are loads that (normally) don’t run at the same time. For example, the heating and air conditioning system is considered a noncoincident load. Where you have such a situation, use the larger of the two loads for your load calculations [220.60].
The final subsection in Part III talks about the feeder or service neutral load. This is the maximum net calculated load between the neutral conductor and any one ungrounded conductor [220.61(A)]. For 3-wire, 2-phase or 5-wire 2-phase systems, multiply this number by 140%.
A feeder or service supplying permanent household cooking equipment and electric dryers can use an additional demand factor of 70% [220.61(B)(1)].
You can’t apply reductions of conductor capacity to any portion of a circuit consisting of non-linear loads supplied by a 4-wire, wye-connected, 3-phase system.
