The National Electrical Code (NEC) is designed strictly as a safety measure to protect you and your property. It is not meant to be an instruction manual for amateur electricians or to be used as a design specification for your home or business. The NEC covers most, but not all, electrical installations.
If you have to change a fuse or check a circuit breaker in an area where the floor might be damp, lay down a piece of plywood first. Standing on this will keep you on dry ground, which is less hazardous than damp concrete. You also should wear dry, rubber-soled shoes and leave one hand in your pocket to keep from inadvertently becoming a pathway for the electrical current.
When replacing lights, don't assume you can install a light with higher wattage. The circuit might not support the additional power demand. You always should confirm the total demand by other lights, receptacles, or appliances before changing an existing fixture.
Electricity is the movement of electrons. A conductor holds its own electrons loosely, so current can easily pass through. Metals, such as copper wire, are good conductors for carrying electric current. An insulator has tightly held electrons, which means current does not flow through it. Plastic, used to wrap around copper wire, is a good insulator, as is cloth, which was once used for the same purpose.
The history of electricity and electrification is full of pioneering scientists, each building on the knowledge of the others.
A two-pronged plug adapter used to convert three-pronged plugs for use in older receptacles also can be used for adapting polarized plugs. The adapter enables them to be plugged in to nonpolarized outlets.
A branch circuit is separate and independent from any other circuit. It has its own circuit breaker or fuse, wiring, and loads. Your service panel has a number or branch circuits for both 120- and 240-volt loads.
CPSC research indicates that homes containing aluminum wire manufactured before 1972 are 55 times more likely to have one or more connections reach "fire-hazard condition" that home wired with copper. These conditions are defined as receptacle cover-plate screws reaching a temperature of 300ºF, the presences of sparking, or charred material around the receptacle. Wiring produced after 1972 solved some, but not most, of the material's failings.
A voltage tester and a receptacle analyzer are two inexpensive but indispensable tools for testing your circuits and electrical devices.
A double-insulated tool doesn't have a ground pin in the plug. Instead, the wire conductor is surrounded by additional nonconductive material such as plastic. This does not guarantee against shock in the even of frayed wiring or damage to the tool. Metal casing also can be lined with nonconductive material.
As a do-it-yourselfer, you want to handle your electrical work at least as neatly and as safely as a professional electrician.
Every switch and receptacle has a specific purpose: they're not interchangeable.
Always calculate the existing and potential load of a circuit before you add on to it.
The more carefully you plan your work and routing for circuits around finished walls and ceilings, the few repairs you'll have to do later.
A panelboard directory, or circuit directory, is the formal name for your list of circuits. (I discussed this previously when creating a circuit map.) Every electrician makes a directory when installing a service panel.