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AFCI
Electrical arcing and a ground-fault are different phenomena. As such, the devices to protect against them are also different, although they have similarities.
An arc-fault current interrupting (AFCI) receptacle has the same two buttons as a GFCI, but a more complex sensor. It doesn’t just detect conditions that can cause arcing before the arcing actually happens. It can also distinguish dangerous arcing from the normal arcing that occurs when you flip a switch, turn on a light or start an appliance.
The purpose of arc fault protection is to prevent fires, and the NEC has steadily increased the number of rooms in which AFCIs are required to cover practically the entire house. It’s becoming standard practice to install dual-function AFCI/GFCI breakers in the main service panel rather than individual combo receptacles throughout the house. It’s cheaper that way, and breakers provide more comprehensive protection.
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Polarized Plug
Some appliance plugs have only two prongs. If they’re different sizes, the plug is polarized. It will only plug into a receptacle with slots the same sizes as the prongs. Plus, you can only insert it in one direction. This is a safety strategy to prevent a ground-fault condition. The wide prong must be connected to the neutral conductor.
Appliances and portable lamps with polarized plugs are internally wired so the hot leg of the circuit terminates at the switch. Only after you engage the switch will power flow to the internal machinery or light bulb.
A good example is a table lamp. The wide prong connects to the neutral conductor of the circuit. This in turn connects to the metal screw threads of the lamp socket. The hot wire, via the switch, connects to the brass knob on the bottom of the socket where no one can touch it. If the wiring were reversed, you could get a shock when changing a light bulb or groping for the lamp switch in the dark.
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Outlet
Certain electrical terms mean different things to laymen and tradesmen. People usually refer to a wall plug as an outlet, but that isn’t what electricians mean by the term. An outlet is any location in a circuit that supplies electricity. It can power a light fixture, a smoke alarm or a hardwired appliance, as well as a wall plug, which is more properly known as a receptacle.
Electrical outlet box locations are typically established during the rough-in phase of electrical wiring, before drywall covers the framing. The electrician runs cable to the outlet box locations and secures it inside the electrical box as required. The electrician then circles back to make-up all the wires and splices inside the outlet boxes and add labels.
After the walls have been covered, the electrician simply connects the prearranged wires to whatever device, light fixture or appliance that is supposed to be installed at that location.
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