National Electrical Installation Standards

Standards as High as Your Own

Wednesday, September 5, 2018


There are 2 sections I'd like to be clarified 1. Load calculations per 220.40 2. Grounding per 250 service grounding. - 2

Bob Gregg



Hey Bob here is the answer to your second question. A Service is defined in Article 100 as the conductors and equipment for delivering electric energy from a utility to premises wiring. A grounding electrode conductor must be connected to the grounded service conductor (often also a neutral conductor) as stated in 250.24(A). A main bonding jumper must connect the, the grounded service conductor to the equipment grounding conductor(s) and service disconnect enclosure within that enclosure as stated in 250.24(B). The service grounded conductor must be installed as stated in 250.24(C) and a grounding electrode conductor as stated in 250.24(D). This is a basic overview of 250.24 for grounded services but there are a lot of details that need to be followed.

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