05/06/2024
Services, Part 2
Mike Holt, NEC Consultant
Service Conductors
Service conductors must have an ampacity of at least the largest of the calculations in 230.42(A)(1) or (2) [230.42]. For example, service conductors must have an ampacity of at least 125 percent of the continuous loads, plus 100 percent of the noncontinuous loads, based on the temperature rating of equipment per 110.14(C)(1) and Table 310.16.
The service neutral conductor must have an ampacity to carry the maximum unbalanced load per 220.61 and not be smaller than required by 250.24(D) [230.42(C)].
Service Disconnect
The service disconnect must be marked to identify it as suitable for use as service equipment and must be permanently marked to identify it as a service disconnect [230.66(A)].
The service disconnect must open all phase conductors [230.70]. It must be placed at a readily accessible location either outside the building or inside nearest the point of service conductor entry [230.70(A)(1)].
Each service must have only one service disconnect except as permitted in 230.71(B). Each service can have up to six service disconnects per 230.71(B)(1) through (5). For example, panelboards with a service disconnect in each panelboard.
The service disconnects for each service must be grouped and marked to indicate the load served [230.72(A)].
Service Conductor Overcurrent Protection
Each service phase conductor must have overload protection [230.90].
The service overcurrent protective device provides overload protection for the line side of service conductors, but not short-circuit and ground-fault protection because that protection can be provided only at the supply end of a circuit.
The rating of the overcurrent protective device must not be greater than the ampacity of the service phase conductors [230.90(A)].
The service overcurrent protective device must be an integral part of the service disconnect or be immediately adjacent to the service disconnect [230.91].
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