Old Wire, New Switch

It can be difficult working with the deteriorated knob-and-tube wire ends inside a box. You might have to snip off the end, and the remaining wire can be a little too short to easily connect to a new switch or receptacle. In this case, you can pigtail a short, new piece of wire to the existing wire and connect the pigtail to the terminal screw on the device. This also will bring the wires into compliance with the NEC, which calls for six inches of workable wire length inside a box. The following diagram shows this type of pigtail.

Dimmers

You can replace any interior single-pole switch with a dimmer if the box is large enough to accommodate the larger body of the dimmer. Don’t try to pack it into a tight or overcrowded box because this is a fire hazard (see the instruction sheet that comes with the dimmer). Dimmer switches come with about four inches of their own wiring or lead wires (line and load and ground wire) ready to connect with cable from the circuit with wire nuts.

The Great Outdoors

You cannot replace an outdoor switch with an indoor switch unless you also use a bubble-type cover or a cover with a flip-style lid. These are weatherproof covers. Better yet, you can use a cover with a built-in, horizontal, lever-type switch that comes with a foam gasket between the cover plate and the box. The lever activates a regular toggle switch underneath. Other than that, the replacement procedure is the same as a regular single-pole switch.

Continuity Coming Up

A continuity test will tell you whether a switch’s metal components, which are critical for the flow of the current, are intact or broken. A continuity tester is battery-powered and provides a current that passes from the tester’s clip through a device or fixture. The tester’s other component is a probe that lights up if a current is passing through the device as designed. To perform the test, a switch or fixture must be disconnected from its power source and removed. (The tester will supply the current for the test.) A continuity tester should never be used on a live current.
The following figures show you how to do a continuity test on a single-pole switch and a three-way switch. If your tests show you that the switch is the problem, it’s time to replace it.
If your tests show you that the switch is the problem, it’s time to replace it.

Checking the Devices

Switches, appliances, and fixtures test a bit differently than receptacles. The first three are tested for continuity and power and require both testing tools. A continuity tester will indicate whether the circuit’s pathway within the switch has any breaks in it from metal fatigue. It also checks other appliances and fixtures for similar breaks. Let’s start with testing for a switch.
Follow these steps to test a switch for power:

1. With the switch off, touch one of the voltage tester’s probes either to the bare end of the ground wire (the inside of the wire nut holding the neutral wires together) or, if it’s a metal box, to the side of the box.
2. Place the other probe against each black wire either at the terminal screw or at the back-wired slot.
3. The bulb should light up for at least one of the hot wires, the line wire coming from the panel or fuse box. If the tester does not light up for either black wire, the problem is somewhere in the circuit between the panel and the device. (Go to step 4 if it does light up.)
4. Turn the switch on and check the other black wire, which is the load conductor. If the bulb on the tester does not light up, the switch is bad and needs to be replaced.
5. If both black wires show current passing through them, recheck the fixture and the appliance because the problem is not with the switch.
6. Note: In some older homes with knob-and-tube wiring, the neutral wire has been switched and used as a “hot” conductor. This makes the task of troubleshooting much more difficult. If you have any questions or concerns while testing, call an electrician.

Brass: New and Old

Many older homes have original brass cover plates, often with a dark bronze tone. These will readily take to a buffing wheel and will come out a fine, shiny brass if that’s your preference. New replacement brass plates also are available. Some homeowners and designers install them in kitchens and bathrooms, but such damp locations aren’t the best places for brass unless you like polishing them from time to time. If you go to any good-size street fair, at least in a large city, you’re likely to run into an artist’s booth selling ceramic electrical plates. Some have a theme (such as stars or suns); others are a little more whimsical. Check to see if they’re listed by UL; if they’re not, decide whether you think it’s a problem. These plates are usually ceramic, nonconducting material and can be pricey.
Local gift and design shops might carry these types of plates as well. They usually are purchased for a single room, such as a bathroom or a baby’s room, rather than an entire home.

Check the Cable Box Size

Boxes come in different sizes based on the installation need. Rectangular boxes, the most common ones used for single devices, generally are two inches by three inches for residential use. Depth ranges from 15/8 inches to 319/32 inches. The deeper the box, the more wires it can accommodate and the easier it is to tuck in the wires and install a device and still meet code. You’ll really appreciate this when you’re dealing with 12-gauge wire.
A round box with
extendible bars.
How many cables can your box accommodate? Well, the bigger the box the better, but to be more exact …

• Count the number of intended cables for the box. Each hot and neutral conductor counts as one wire each, and all the grounding conductors together count as a single wire.
• Take this total and add one for any cable clamps (if they’re the same type of clamp). If you have two different types, you have to count each as a separate number.
• Take this new total and add two for each device (switch or receptacle).
• If the box contains 14-gauge wire, multiply the total number (of wires, clamps, and devices) by 2 cubic inches. If 12-gauge wire is being used, multiply the total by 2.25 cubic inches.
• The result of this multiplication is the minimum allowable volume of wires, clamps, and devices for that box.

(The volume of a box usually is stamped on the back of the inside of the box.)
Let’s say you have a light switch in a plastic box with two 14-gauge cables coming
into it. (One is the line; one is the load.) This gives you two hot conductors, two neutrals,
two grounding conductors (these count as one wire in our calculations), and
one switch. Therefore …
Two hot conductors: 2
Two neutrals: 2
One grounding conductor: 1
Device: 2
Total: 7
7 2 cubic inches = 14 cubic inch minimum box size (Note: Most plastic boxes do not have any type of clamp.)

Plastic or Steel Cable Boxes?

Both plastic and steel boxes are used in residential construction. A box has to withstand a certain amount of construction trauma when it’s installed and later when drywall is installed around it. (Drywall hangers are not necessarily kind and gentle people, at least not when they’re getting paid by the square foot.) Plastic boxes are lightweight and are easy to install, especially those that come with nails for direct attachment to a wall stud or a floor joist.
Metal boxes are standard in most commercial work. Unlike a plastic box, a metal box is a good conductor of electricity and must be grounded along with the device or fixture. Special fittings are used to connect a metal box to conduit and conductors to the box. These fittings include an array of clamps, clips, and locknuts, most of which you’ll never use in the course of residential repairs and remodeling. A plastic box works well for a single gang or device use, but some electricians find that a larger plastic box’s shape distorts during installation or when the drywall is installed. For these reasons, they use tougher boxes, either Bakelite (reinforced phenolic) or metal for two gang installations and metal for three gang. The larger the box, the more difficult it is to keep it level and in line.

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.

Electrical Switches

The most common switch in your house is a single-pole switch with a toggle marked “On” and “Off.” It typically is used to control a light fixture or a receptacle. Single-pole simply refers to electricity flowing in one direction. In most cases, one black (hot) wire is connected to one terminal screw (or it might be back wired), and a second hot wire is connected to the other terminal screw, proceeding on to the light. In terms of physics, a pole is just one of two opposite points on a magnet that manifest the magnetic properties. (Remember, a spinning magnet, called a dynamo, at your utility’s power plant creates the electric current.) Unlike older switches, modern versions often come with a ground terminal for the green or bare copper ground wire.
A single-pole switch controls the current to its load from one location only. Other witches control the current from two or even three different locations