Responsibility for adequate grounding on the customer’s premises lies with the customer and not with the utility company.

Grounding is one of the most important subjects covered by the National Electrical Code and this code is very clear in regard to the purposes of grounding. It reads:

Circuits are grounded to limit excessive voltages from lightning, line surges, or unintentional contact with higher voltage lines and to limit the voltage to ground during normal operation.

The National Electrical Code requires the grounding of one conductor of electrical systems in which the voltage to ground does not exceed 150 volts. One of the wires in a single-phase, three-wire system, and also in a four-wire wye system is called the neutral conductor and is grounded within the company distribution system.

This same conductor, whenever brought onto the customer’s premises, must again be connected to a ground at a point as close to the entrance to the structure as possible, but at no other point. Since a two-wire system comprises the neutral conductor and one line conductor, the grounding of the neutral in the two-wire system follows the same rules as those applied in the three-wire system.

Grounding at one point only on the customer’s premises guards against the possible hazards due to difference in ground resistance. Also, with only one ground, it is easy to check the presence and adequacy of the grounding circuit.

In residential wiring systems, not only must the neutral conductor be grounded, but exposed metal such as cabinets and conduits which might come in contact with ungrounded current-carrying wires must also be grounded.

Most commonly, the ground connection to the neutral wire is made in the first switch, distribution panel, or meter mounting device installed as a part of the service equipment. The ground connection must be made on the supply side of the customer’s switch.

At this point, the neutral wire is connected to the metal enclosure, meter socket, or switch box and grounding of both neutral wire and “non-current-carrying parts” of the system is effected by one grounding conductor. There is, however, an important distinction. On the supply side of the service-disconnecting device, the grounded conductor may be used for grounding the meter socket or trough and service equipment.

On the load side, this grounded conductor shall not be used to ground equipment or conductor enclosures. Exceptions to this rule are made only for the frames of 120/240 volt electric ranges and electric clothes dryers which may be grounded to the neutral conductor of a three-wire circuit.

In city areas where there is a public water system, the grounding wire is connected to the water pipe near the point it enters the building.

To avoid corrosion, connectors for use on copper pipe should be made of copper; those for use on galvanized pipe should be made of galvanized iron. In areas not served by an extensive public water system or where plastic pipe is used, there can be difficulty getting a dependable ground connection.

A satisfactory ground connection is one which presents a low resistance to the flow of electric current. Such a ground connection usually consists of a rod, at least eight feet in length, driven into the ground adjacent to the building served.

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