ELECTRICAL SERVICES

Bonding

Bonding Metal Service Components
1. Connect (bond) together all metal non-current carrying components in an electrical system so that any current imposed on the components will be safely carried to ground. Such components include metallic conduit and tubing, cabinets, and junction boxes. Read the full Topic

Electrical Service Load Calculation

Limitations of the Material in this Section
We do not recommend that most readers of this book determine electrical service load. Leave this to experienced electrical contractors. For readers who are interested in how to calculate service loads, we provide the following explanation.

Electrical Service Minimum Size
1. Provide at least (≥) 100 amp service to a single family dwelling unit.
2. Provide at least (≥) 60 amp service to an accessory structure. Exceptions to the 60 amp minimum service exist for one and two circuit service to some accessory structures. Read the full Topic

Electrical Service, Feeder, and Grounding Electrode Wire Size

Service, Feeder, and Grounding Electrode Wire Size
1. Use the following table to determine the minimum wire size for service entrance, feeder, and grounding electrode wires. This table applies to service entrance wires, and to feeder wires serving the entire dwelling, and to feeder wires serving accessory structures that require at least (≥) one 240 volt circuit or more than (>) two 120 volt circuits. This table applies only to wire with insulation types THHW, THW, THWN, USE, and XHHW.
2. Refer to Sections 3607 and 3608 for information about grounding electrode wires and grounding electrodes. Rod in this table means that the grounding electrode is a driven rod or a pipe installed according to Section 3608. Ufer in this table means that the grounding electrode is encased in concrete and installed according to Section 3608. Other in this table means that the grounding electrode is one of the other grounding electrodes allowed by Section 3608. Driven rods, water service pipes, and concrete encased electrodes are used as grounding electrodes in most homes.
3. Refer to Section 3704 in Chapter 37 for information about calculating the grounded (neutral) conductor size. While the grounded (neutral) conductor is often 2 sizes smaller than the grounded (hot) wire, this general rule is not technically correct. The grounded (neutral) conductor size should be calculated. Read the full Topic

Electrical Servies General Requirements

One Electrical Service Per Dwelling Unit
1. Provide only one electrical service per dwelling unit. This usually means one electric meter and one main service disconnect per building. Att ached townhouses are considered separate buildings and usually have one electrical service per townhouse unit. Duplex and other two-family buildings are not considered separate buildings, although they are separate dwelling units. Check with the local building offi cial before any project that contemplates providing an additional electrical service to a building.

Electrical Service Run Through Building Interiors
1. Do not run service wires that serve one building through the interior of another building. A building’s interior includes the attic, basement, and crawl space. Service wires are considered inside the building even if they are run in conduit. Service wires that are encased in concrete or buried underground are not considered inside a building’s interior. Read the full Topic

Grounding Electrode

Connect (Bond) All Grounding Electrodes
1. Connect (bond) together all grounding electrodes that may be available at a building. This includes underground metal water pipe, reinforcing bars or wire in concrete, ground rings, and ground rods. The IRC does not require that all possible types of grounding electrodes be installed. It requires that if a grounding electrode is installed, it must be connected (bonded) to all other grounding electrodes and to the neutral (grounded) wire.
2. You are not required to bond reinforcing bar in an existing building’s foundation if the bar cannot be accessed without disturbing the foundation.
3. Use a bonding jumper at least (≥) as large as the grounding electrode wire to connect (bond) the grounding electrodes. You may connect bonding jumpers between grounding electrodes at any convenient point.
4. Connect the grounding electrode wire at any convenient grounding electrode. Read the full Topic

Service Drop Clearances and Installation

Service Drop Clearances to Decks and Openings
1. Provide at least (≥) 3 feet clearance between service drop and service entrance wires and porches, decks, stairs, ladders, fi re escapes, balconies, sides of doors, and sides and bottoms of operable windows (not the tops of operable windows even if the top sash is operable). Clearance is required only to service drops and service entrance wires that consist of individual wires that are not protected by a raceway or outer jacket. This means that clearances are usually required for utility service drop wires and are not required for SE type service entrance cable and for wires or cables installed in conduit or tubing.

 

Read the full Topic

Service Entrance Wire and Mast Installation

Service Entrance Wire Insulation
1. Insulate hot (ungrounded) service entrance wires with approved insulation.
2. You may use uninsulated copper wire as the neutral (grounded) wire if it is inside a raceway or if it is part of a service entrance cable or if it is buried in an approved manner.
3. You may use uninsulated aluminum wire as the neutral (grounded) wire if it is part of a service entrance cable or if it buried in an approved manner.

Service Entrance Cable Protection Against Damage
1. Run above ground service entrance cable inside approved conduit or tubing (such as RMC, IMC, EMT, Schedule 80 PVC) if the wire is subject to physical damage and if required by the local building official. Places where service entrance cable might be subject to physical damage include near driveways and walkways and where doors, shutters, or awnings might impact the cable.
2. Use service entrance cable labeled as sunlight resistant if the cable is exposed to any direct sunlight. Read the full Topic

Service Grounding General Requirements

Service Grounding
1. Connect the neutral (grounded) wire to the grounding electrode wire at the nearest accessible point at or before the service equipment (main disconnect). The service equipment is usually the most convenient accessible grounding point because the meter enclosure and points before it are  usually locked or secured and not accessible. The grounding electrode wire connects the neutral (grounded) wire to a grounding electrode.
2. Do not connect the neutral (grounded) wire to ground at any other place downstream from the service equipment grounding point. An exception to this rule exists when two buildings are supplied by one electric service.
3. Connect (bond) all metal parts of the electrical system to the neutral (grounded) wire. This includes service equipment and panelboard cases, any metal electrical conduit or tubing, all metal pipes in the building (such as metal water and gas pipe).

 

Read the full Topic