Electricity is a vital part of our everyday lives. We use it for lighting, heating, cooling, cooking and many other things. When electricity goes out, our normal activities are interrupted and sometimes our safety is put at risk. Electric utility crews are the unsung heroes of society that work tirelessly to restore electricity when it is out. These brave men and women, working in the rain, snow and freezing temperatures, are the first line of defense for our families and communities.
Electrical Service refers to the conductors, materials and equipment that transfer power from the utility system to the wiring system that supplies a building with electrical energy. This includes the service drop, the service panel, and all components connected to it. It also includes a main disconnecting means on the outside of the building. The rules of the National Electrical Code (NEC) apply to the entire system up to and including this point, unless local provisions or codes specify otherwise.
The service drop is a set of overhead wires that connect the utility electric power supply system to the service entrance conductors at the customer’s building. The service drop may consist of one or two wires that carry either 120 volts or 220 volts. The wires are usually a solid core, bare metal, or insulated and include the neutral and hot legs. The service drop is the responsibility of the utility company, except for the point of connection to the customer’s revenue meter base and service riser, which are the responsibility of the customer.
In some areas, the electrical power is delivered underground instead of overhead. This is especially common in older neighborhoods and rural settings. Regardless of the type of service, a professional should always be cautious when touching any part of the electrical system, especially the service wires. Screwdrivers, wire cutters and strippers, pliers, and other tools can all cause an electric shock if they come in contact with a live wire.
Once the power is received at the building, it flows through a service panel that contains individual branch circuits that run through the house. Each branch circuit is a group of fuses or circuit breakers that protect different areas and outlets of the home from damage due to overloading a circuit, improper usage, or an external event such as a lightning strike.
It is important for the design engineer to determine the type of electrical service to be provided, and then build the correct service equipment. The service equipment must be sized to accommodate the load requirements for the project. This can be done using an electrical service data chart. This chart, combined with Item 628 and ED standards, can provide the contractor with enough information to build the correct service equipment for the project. The sizing is based on the amount of current that is required to operate the loads. The design engineer should carefully study the available load in the area and calculate the load factor to ensure that the proper equipment is used.