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The requirements for feeders and service conductors are essentially the same as for branch circuits. The termination provisions in Section 110.14(C) are the same as the requirements of Section 310.15 for sizing a conductor based on the conditions of use. There is one significant difference for feeders and service conductors.Section 215.2 & Section 230.42
Sections 215.2 and 230.42 establish minimum conductor sizes based on continuous and noncontinuous loads and based on the typical noncontinuous rating of an overcurrent device.
However, Section 215.2(A)(1), Exception No. 2 Exception No. 2 This exception for the grounded conductor does not apply to branch circuits, because of the nature of the terminations on both ends of a branch circuit: typically an overcurrent device on one end and an “appliance” termination on the other. A grounded feeder or service conductor will usually terminate on a bus bar like that in a panel board or a switch board. also explains that grounded conductors that are not connected to an overcurrent device are not required to be increased in size for continuous loads. The same exception applies in Section 230.42.
Another thing to keep in mind with feeders and service conductors is that both of them have likely had some kind of a demand factor applied when the load is calculated in accordance with Article 220, because frequently they supply lots of loads, not all of which operate at the same time. Branch circuits for the most part are going to be sized to handle all the load that is connected to them, and it is generally assumed that the entire load could be on at the same time.
© Hughes Associates,Inc. 2012