Everything You Need to Know About Electrical Codes to Safely Power Your Home
Learn information on national and local electrical codes, tips for having an inspector approve your work, how to load and ground circuits, and more.
If you're replacing an existing light fixture, switch, or power outlet, there's usually no need to contact your local building department. But when you run new electrical cable for new service, you'll want to be sure to work with a building inspector and comply with all local codes. This guideline applies to projects that involve wiring several circuits or adding an electrical receptacle. It's important to diligently follow both national and local electrical codes to ensure all components are installed safely and function properly. These codes exist to protect you and your home, so you should consult them carefully before you begin a remodeling project or install new electrical equipment. Verifying that your electrical work is up to code can help reduce the risk of fire or electrical shock.
To help you make sense of the various electrical codes, we'll walk you through some of the most common general requirements for home electrical systems, plus offer some general how-to tips for safe electrical work. This helpful information will give you a general idea of what electrical inspectors need to review before approving your work. Refer to this guide on electrical codes, including specific requirements for individual rooms, to make sure your electrical installation goes smoothly and safely.
National and Local Electrical Codes
Professional electricians often refer to the National Electrical Code (NEC), a massive volume that describes national codes for residential and commercial wiring. You don't necessarily need to buy this book, but you might need to refer to a library copy or an online version from time to time.
Local building departments often modify the NEC, and you must satisfy those local codes. It's not unusual for adjacent towns to have very different codes. For instance, one area might allow plastic boxes while another requires metal boxes. Have a local inspector approve your wiring plans before you begin work.
If existing wiring does not meet local codes, chances are that your building department will not require you to change the wiring. Usually, only new electrical work must be up to code. However, if the old wiring is unsafe, you should change it. Extensive remodeling could also require you to bring the entire house up to current codes.
Loading and Grounding Circuits
Any electrical plan, however simple or complex, must start with two considerations. First, make sure the new service doesn't overload a circuit. Second, see that all receptacles and appliances are safely grounded. Local codes probably require that switches and light fixtures also be grounded. Grounding protects against shock in case a wire comes loose or an appliance or device malfunctions. Check using a receptacle analyzer ($5, The Home Depot).
All receptacles and appliances must attach to a ground wire (or metal sheathing) that runs to the service panel. Check with local codes to determine the approved method. A thick ground wire should emerge from the service panel and clamp tightly to a cold-water pipe or grounding rods driven into the ground outside the house.
If the box is plastic, connect the ground wire to the receptacle only. For a middle-of-run receptacle (shown above), splice the ground wires together and connect to the receptacle with a pigtail.
With a metal box, attach ground wires to both the receptacle and to the box using a grounding screw. Use a pigtail and a grounding wire nut.
Systems that use armored cable or metal conduit might have no grounding wire. The sheathing or conduit provides the path for ground, so it must be connected firmly at all points.
Common Electrical Code Requirements
Here are some of the most common general requirements for home electrical systems. Local building departments might have different demands.
Boxes: Plastic electrical boxes are common throughout much of the United States and Canada, although some localities require metal boxes. Buy large boxes so wires aren't cramped. Attach them firmly to a framing member whenever possible or use remodel boxes that clamp to the wall surface.
Receptacles, fixtures, and appliances: New receptacles and appliances must be grounded. Fixtures and appliances should be approved by Underwriters Laboratories (UL).
Cable: Nonmetallic (NM) cable is the easiest to run and is accepted by most building departments. Wherever cable is exposed rather than hidden behind drywall or plaster, armored cable or conduit might be required.
Circuits: Most 120-volt household circuits are 15 amps, and all lights must be on 15-amp circuits. In kitchens and utility areas, 20-amp circuits might be required.
Wire size: Use 14-gauge wire for 15-amp circuits and 12-gauge wire for 20-amp circuits. Cable runs longer than 500 feet could need larger wire. Consult your building department.
Service panels: As long as you do not need to add a new circuit, your service panel, even if it is an old fuse box, is probably sufficient. If you add circuits, you might need to upgrade the panel or add a subpanel. Check with an inspector or professional electrician.
What to Know About Electrical Codes in Each Room
Some electrical codes apply to the entire house while others apply to specific rooms. Here are some general guidelines, but note that local codes might vary. These requirements usually apply only to new installations, as older wiring does not have to comply as long as it is safe. These requirements make good sense and are not overly strict. Wiring that does not meet these standards would be either awkward or unsafe.
Bedrooms, living room, and dining room: Every room must have a wall switch located near the entry door that controls either a ceiling fixture or a switched receptacle. All ceiling fixtures must be controlled by a wall switch and not by a pull chain. Receptacles must be no more than 12 feet apart, and there must be at least one on each wall. If a section of wall between two doors is wider than 2 feet, it must have a receptacle. Light fixtures must be on 15-amp circuits. Receptacles are usually allowed to share a circuit with lights. A heavy electrical user, such as a window air-conditioner or a home theater, might need to be on a dedicated circuit.
Hallways and stairways: All stairways must have a light fixture controlled by three-way switches at the bottom and top of the stairs. Hallways might also need a light controlled by three-way switches. A hallway longer than 10 feet must have at least one receptacle.
Closets: There should be at least one overhead light, controlled by a wall switch rather than a pull chain. The light must have a globe rather than a bare bulb; a bulb can get hot enough to ignite clothing, stacked blankets, or storage boxes.
Attached garage: There must be at least one receptacle, not counting receptacles used for laundry or other utilities. There should be an overhead light (in addition to a light that is part of a garage door opener) controlled by at least one wall switch.
Kitchen: Many codes call for two 20-amp small appliance circuits controlling GFCI receptacles placed above countertops. Other codes call for 15-amp split-circuit receptacles. The refrigerator, microwave, garbage disposer, and dishwasher might need to be on separate circuits. The lights should be on a separate 15-amp circuit.
Bathroom: Codes require that all receptacles be GFCI-protected. Any light fixture should have a sealed globe or lens to shut out moisture. A fan/light/heater might draw enough power to require its own circuit.
Outdoors: Standard-voltage wiring requires either waterproof underground feed (UF) cable or conduit or both. The depth at which the cable must be buried varies by local codes. Special waterproof fittings and covers are called for. For low-voltage lighting, standards are less strict, and usually, no permit is needed.