Installing an Electrical Outlet Anywhere
Adding receptacles isn't overly complicated, but there are facts you should know in order to stay safe and code compliant. Longtime electrician Rune Eriksen shares his advice, tips and handy techniques to help you deal with wiring scenarios you may encounter.
Make a starter hole with a screwdriver
Drywall keyhole saws are often called “jab saws” because they can be used to jab through drywall to start a hole. But our expert finds that he damages less drywall when he makes a couple of starter holes in opposite corners with a skinny, flat head screwdriver. When you're cutting, let the saw do the work. Over-aggressive sawing can tear the paper on the back side, which will weaken the drywall significantly. It's important to stay inside the lines; a hole that's too big will be unusable. If a hole ends up too small, you can carve away at the edges with a utility knife.
Find the wall cavity with a clothes hanger
When you're pulling power up from an unfinished basement, a simple way to figure out where to drill the hole for the new cable is to drill a small “finder” hole near the base of the wall and stick a length of wire clothes hanger down through the hole. Our expert uses a wire cutter to make a 45-degree cut and actually uses the cut end to do the drilling. The hanger will bore through carpeting, hardwood floors, subfloor and even drywall. If you're going into the attic, poke the hanger through, and then go downstairs and measure over about 3-1/2 in. (3/4-in. quarter round, 1/2 in. base trim, 1/2-in. drywall and half the width of a 2x4 = 3-1/2 in.). That’s where to drill your new hole.
Patching the finder hole is a piece of cake. The same trick works when pulling power from the attic. Just drill up into the attic where the wall intersects the ceiling. Because there's no trim, measure over only 2-1/4 in. from the hanger instead of 3-1/2 in. If you run out of wire hangers, go to your local dry cleaner, because most stores only sell plastic hangers these days.
Strip cables before pulling them
It's a lot easier to remove the sheathing from the cables before you install the box. Make sure there's at least 1/4 in. of the sheathing pulled inside the box beyond the cable clamp. And at least 6 in. of wire should be left in the box, measured from the front edge of the box opening. After the box is installed, bend the end of the wires using the hole on your wire stripper.
Cut holes in tile with a rotary tool
A rotary tool is a great, safe way to cut through tile. Set the depth of the tile-cutting bit shallow to avoid hitting plumbing or wires in the wall cavity. Whenever possible, use grout lines for two sides of the hole because they're much easier to cut through. Drill starter holes in two opposite corners with a glass-and-tile drill bit.
"Old Work" boxes
There are several kinds of “old work” boxes, sometimes called “remodel” boxes. Some are easier to find than others (but all are available online), and some are easier to install and more durable (details below). Instead of being nailed to a stud, “old work” boxes are clamped onto the drywall. Here are a few of the most common styles:
(A) This tough fiberglass box is a favorite of many contractors although it's a bit more expensive (top). They like it because the rugged clamping system is much more secure than that of cheaper styles. These boxes aren't always available at home centers, but you can find them at electrical supply stores. Or you can go with the “Carlon 70108.” This style works well especially if the outlet gets a lot of use.
(B) This PVC box is the least expensive and most readily available, but it's also the flimsiest. Some pros complain that the clamping tabs aren't strong enough and the screws strip out the plastic.
(C) This fiberglass box is a good choice. It's reasonably priced , available at many home centers and stronger than the PVC version.
Fold wires into the box
Our expert connects all the wires together and then runs short individual wires (pigtails) to the receptacle. Pigtails also ensure that the rest of the circuit remains energized downstream even if this receptacle fails. Try to fold all the wires as neatly as you can and push them into the back of the box. Cramming receptacles into a crowded box can result in loose connections and damaged wire insulation, which can cause a fire.
Use the same gauge wire
If you're pulling wire from a circuit that has 12-gauge wire, don't install 14-gauge wire to the new receptacle or vice versa. The new receptacle should be wired with the same gauge wire as the source.
Trim metal supports
Our expert prefers working with the “old work” boxes with metal flanges. They provide more support than the boxes with flip-out wings. One drawback of these boxes is they aren't made for thicker walls. So when you need to add a receptacle to a wall with drywall and thick wainscoting, we recommend cutting about 3/4 in. off both metal flanges with aviator snips before installing it. Make straight cuts or the box will end up crooked in the hole.
Where to get power
When you're choosing which circuit to add on to, the ease of pulling the wire to the new receptacle will likely be the most important factor. Here are some acceptable options.
DO add on to these circuits:
- General-purpose receptacle circuits in living areas, attics and unfinished basements.
- Light switch and light fixture locations where un-switched 120-volt power is available.
- Smoke detector locations.
You can't add on to just any circuit in your house. Here are some circuits you definitely want to avoid.
DON'T add on to these circuits:
- Dedicated kitchen, bathroom and laundry circuits.
- Individual circuits for motor-operated appliances like garbage disposers, refrigerators, furnaces, dishwashers and trash compactors.
- Circuits for specialty appliances like microwave ovens.
- A box with too many wires.
AFCI protection for the whole circuit
When you're pulling power from a source other than a receptacle (such as a light fixture or smoke detector), the new cable and receptacle will need to be arc-fault circuit interrupter (AFCI) protected. If there are no receptacles upstream where you could install an AFCI-type receptacle, you have no choice but to protect the entire circuit by installing an AFCI circuit breaker at the panel.
Install an AFCI receptacle at the source
Newer electrical codes require arc-fault circuit interrupter (AFCI) protection for all branch circuits supplying receptacles, switches, light fixtures, smoke detectors, etc., in essentially all locations in the dwelling except bathrooms, basement storage areas and garages. AFCI circuit breakers and receptacles are designed to detect dangerous, abnormal arcing in branch circuits and cut off the power before a fire can start.
When you pull power from an existing receptacle for a new receptacle, the electrical code requires AFCI protection for both the existing wiring and the new wiring. The easiest way to do this is to install an AFCI receptacle at the first receptacle outlet of the existing circuit. The AFCI receptacle will provide downstream protection for the majority of the existing circuit and the new extended wiring too.
How to calculate electrical box size
Use this chart to determine the correct electrical box size.
Tamper-resistant receptacles are designed to help prevent children from shoving a metal object into an outlet. Tamper-resistant receptacles are now required at all indoor and outdoor locations for dwelling units.
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