They’re Not All the Same

The following is a list of the most common electrical boxes:

• Rectangular for switches and receptacles
• Square for junctions or two receptacles/ switches
• Octagonal and round for ceiling fixtures
• Retrofit types for inserting into existing walls and ceilings
• Aluminum and PVC plastic for exterior use
• Boxes with extendible bars or braces for attaching between joist
• Pancake boxes for limited circumstances when a regular box is too deep for the wall or ceiling space (Most of the plastic ones are not listed as tested by UL, and the metal ones are rated for only one cable, usually 14 gauge.)
• Fan-rated boxes—the only boxes you can use to install paddle fans

Don’t Forget the Boxes

The NEC code requires that any wires connected to each other or attached to a fixture or device must be enclosed in a box with a cover plate. This means that receptacles, switches, lights, wall heaters, anything that requires electricity will have its wiring housed in a box. A box serves a number of purposes:

• It serves as a point of attachment for a device or a fixture. (It has to be screwed to something.)
• It keeps wires that could short and then spark away from wood framing, decreasing the possibility of fire.
• It protects people from accidental exposure to wires and possible shock.

There are boxes for every purpose: ceiling lights, retrofitting fixtures into existing walls, weatherproof designs for outdoor use, and junctions for wire connections that aren’t immediately attached to a device or fixture. As with switches and receptacles, you’ll have to choose the right box for the job at hand.

Receptacles Galore

Most of the receptacles in your home are the duplex type and have been in common use for the better part of the century. Current versions differ from those used through the 1950s because the newer ones have a grounding hole. Polarized receptacles came into use in the 1920s. The different-size slots (the longer one always goes with the neutral wire, the shorter with the hot) maintain consistent, directed current flow along the respective hot and neutral wires. The earliest receptacles were an odd arrangement. The plug-in part of the outlet was actually a screw-in affair, something like a light bulb. The receptacle plate had a small flap that flipped up to reveal a socket into which the plug-in was screwed. (Hey, electrification had to start somewhere.)
The following are specialized types of duplex receptacles:

• Floor receptacles
• Clock receptacles
• GFCIs

Floor receptacles are specially designed to withstand foot traffic. They are installed in the middle of large rooms or in other areas far away from a wall receptacle. They often are seen in offices and other commercial settings with large, undivided floor spaces.
A clock receptacle is recessed so that a clock and its cord can be hung flush against a wall. You used to see these more often in kitchens, but you don’t see them as often now, especially since the advent of inexpensive battery-powered wall clocks. This type of receptacle is now more common for plugging in microwaves and for picture lights that plug in behind pictures and paintings.
A GFCI can be used for a single location such as a bathroom or a kitchen, or it can offer protection to an entire circuit of receptacles or other loads. This is possible only if the GFCI is the first receptacle on a circuit. From that point on, anything beyond it on the same circuit will have GFCI protection. If it’s in the middle of a circuit or in any other position than the first receptacle, it will not offer any protection to any load between it and the service panel.

Timers and Doorbells

Timers, either manual or automatic, also are types of switches. Manual timers regularly are used with bathroom fans and heat lamps. A frequent residential use of automatic timers is to control a whole-house ventilation system. Doorbells are switches, too. When you press the button, a low-voltage current flows to the chimes or the buzzer. Thermostats are another low-voltage switch, except these are activated by temperature changes. Elaborate thermostats have separate switches for controlling the furnace fan and for turning heat and air conditioning on and off manually.

Dimmers

In addition to their romantic value, dimmer switches enable you to decrease the lighting in the dining room so your kids can’t see that you’re feeding them Brussels sprouts, a side dish that no human being should ever eat anyway. Dimmer switches come in several styles including those with …

• A toggle control.
• A dial control.
• A sliding control.
• Automatic dimming.

A dimmer reduces the voltage reaching a light fixture, but in doing so, the switch builds up a small amount of heat. Because of this heat and the large size of a dimmer switch compared to other switches, it might not work as a replacement for an existing switch if you have an undersized or crowded box.

Pilot-Light Switch

A pilot-light switch resembles a standard singlepole switch, except it has a built-in bulb (either the toggle is illuminated or the bulb is on the face of the switch) that lights up when the switch is in the “On” position. This usually is installed when the fixture or light is out of sight of the switch (say, a light in a detached garage). The illuminated switch lets you know if someone forgot to turn the lights off.

Ganging Up

Switches for multiple light fixtures often are ganged up in one box. If all the lights are on the same circuit, one feed wire from the panel will supply the power for all the switches and their loads. A separate cable will run to each fixture. Sometimes you’ll run across a single gang box with a double switch, but this isn’t very common in residential systems.
How many switches can you fit in one box? Leviton offers one switch plate that has space for 10 switches. You’ll find these in commercial settings or maybe in an Internet gazzillionaire’s new mansion.

Switch/Receptacle Combo

This handy device is half receptacle and half switch. It’s a quick way to add a receptacle to a room (after you’ve calculated the amperage of the new load—remember not to overload your circuits). The receptacle will be at switch height, which typically is four feet from the floor to the top of the receptacle box. The switch and the receptacle can operate independently of each other, or the receptacle can be controlled by the switch, perhaps for a hanging ceiling lamp not directly wired to a circuit that came with a lamp cord and plug.

Four-Way Switch

This one is always found between a pair of three-way switches. You’d have to have a really long hallway or a large room needing switch controls from three locations. A four-way switch comes with two pairs of color-matched terminal screws that conveniently connect with color-matched wires from the two three-way switches.

Three-Way Switch

Three-way switches come in twos so you can control a light from two locations. Their most common location is at the top and bottom of a staircase or at opposite ends of a large room with more than one entrance. Three-way switches come with three terminal screws: Two are the traveler screw terminals; the third, which is darker in color, is the common screw terminal. The traveler terminals connect one switch to the other. The cable that runs between the switches has two hot wires: one neutral, and one ground.