Wire types for North American wiring practices are defined by standards issued by Underwriters Laboratories, the Canadian Standards Association, the American Society for Testing and Materials, the National Electrical Manufacturers Association and the Insulated Cable Engineers Association.

Knob-and-Tube

Knob-and-tube wiring is so named because of the porcelain fittings used to support and insulate the conductors from the timber components in the home. The knob holds the wire away from rafters and joists, while the tubes are inserted into holes bored though joists and studs to protect the conductor and its rubber insulation.

Circuit Breaker Panels

These are probably the most common type that home inspectors will come across, as they have replaced fuse panels over the last 40 years or so. As we saw for fuse panels, breakers are far from foolproof and require some particular checking.

Moisture

A crucial point to always bear in mind is that water can be a very good conductor of electricity. Any panel that is damp or wet should NOT be touched or opened by an inspector.

Remote Distribution Panels

Although this topic is covered in other areas, because the emphasis is on safety, it's important to review.

The purpose of bonding is to ensure the electrical continuity of the fault current path, provide the capacity and ability to conduct safely any fault current likely to be imposed, and to aid in the operation of the over-current protection device.

What Is Grounding?

Generally speaking, the difference between grounding and bonding is: Grounding is a direct connection to the earth to aid in removing damaging transient over-voltages due to lightning. The purpose of bonding is to ensure the electrical continuity of the fault current path, to provide the capacity and ability to conduct safely any fault current likely to be imposed, and to aid in the operation of the over-current protection device. Properly bonding all metal parts within an electrical system helps ensure a low-impedance fault current path.

Service Drop

The service drop is the overhead service conductors located between the utility electric supply system and the service point.

The service-entrance cable SEC (blue arrow) is a line of service conductors (white arrows) located between the terminals of the service equipment (main disconnect) and a point usually outside the building, clear of building walls, where they are joined by a tap or splice (orange arrows) to the service drop or overhead service conductors (red arrows).

Plumbing Vents

Depending on location, there are primarily two different types of plumbing vent flashing. The most common in northern climates is the neoprene or metal boot. In Florida and in many other southern states, a lead flashing, which also protects the plastic vent pipe from ultraviolet damage, is more common. The stack vent is provided for the waste stack. The stack vent is the extension of a soil or waste stack above the highest horizontal drain that is connected to the stack. This is the main commonly-observed pipe that is observed penetrating the sloped roof surface, and it may also be visible in the unfinished attic space. This is an inspection image of a stack vent pipe penetrating the roof covering surface.