Service Drop
The service drop is the overhead service conductors located between the utility electric supply system and the service point.
Service Point
The service point is the point of connection between the facilities of the service utility and the wiring at the house. The point of attachment of the overhead service conductors to a building or other structure should be not less than 10 feet (3048 mm) above finished grade.
Overhead Service
In many older residential areas, and practically all rural locations, the electrical supply is delivered to the property via overhead conductors strung on wooden utility poles. The high-voltage lines connect directly to the property through a transformer delivering main power.
While the service overhead belongs to the utility company, the inspector should still evaluate it, particularly to determine the available voltage, its clearances, and any mechanical damage.
The Cable Assembly
Most residential buildings are supplied with 120/240-volt services. This means that the cable assembly is made up of two ungrounded (live or hot) conductors, each supplying 120 volts, with one neutral or grounded conductor acting as the return.
Many homeowners mistakenly believe that the three conductors include one each of a live, a neutral, and a ground. In fact, to have 240 volts available in the home, we need two separately derived 120-volt ungrounded conductors and a grounded conductor. The ground does not return to the pole through the cable assembly; the grounded conductor serves the role of the return path to the transformer.
There are, however, a few variations on the theme. It is not unusual to see one of the live conductors tied back. This is indicative of a 120-volt-only supply, which is still installed in some older properties, apartments and condos. Conversely, the inspector may see cable assemblies with more than three connected conductors. This is typically a 3-phase supply commonly found in both commercial and agricultural environments.
In the case of 120-volt-only supply, we recommend that the inspector's report shows this limitation. In the case of high-voltage, 3-phase supplies, we recommend that the inspector defers this part of the electrical inspection to a qualified industrial or commercial electrical contractor.
Service Cable Connections
(Image above courtesy of member Steve Stanczyk)
The service cables are connected to the service entrance cables by crimped connectors, which are then covered in an insulated sleeve.
The image above shows these insulators missing completely, and a very dangerous condition exists, especially to the unwary home inspector.
Point of Attachment to the Building or Structure
The neutral (grounded conductor) also serves as the main physical connection (though insulated) to the building.
The inspector should ensure that this strain relief is not detached or pulling away from the structure.
On some older properties, the conductors are not in an assembly, and each has its own connection to the structure, but this is rare these days, and probably in need of replacement.
The image above (courtesy of David Macey) shows one of these older connections.
The point of attachment of the service-drop conductors to a building or structure must have a clearance above the finished grade of at least 10 feet.
Clearances
The overhead service must have some minimum separation from both the structure itself and any walkways, driveways, balconies, patios and swimming pools.
Very often, an inspector will see properties that have been modified, and the service overhead should have been relocated but wasn't. This can obviously lead to some dangerous conditions, especially over swimming pools and decks where the service connections could be accidentally reached by the homeowner. Provided by Nachi.org