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While it’s usually easier and neater to run cables inside walls, sometimes surface wiring is the best way to go. It eliminates the hassle of tearing open finished walls and ceilings, and it solves the problem of running power across masonry surfaces. Plus, it eliminates the risk of running extension cords. The easiest and least expensive surface-mount system is EMT (electrical metallic tubing) conduit with metal boxes for receptacles and switches.In this article, we’ll show you the tools, materials and techniques you’ll need to cut, bend and connect a metal conduit system, as well as run wire in it. To illustrate, we chose a garage workbench area that was poorly lit and underpowered. To upgrade it, we added seven receptacles and a switch.
We’ve kept our conduit route and bends very simple for this job, but you can apply the same techniques to a more complex design with a longer run.
All new 4" x 4" x 1-1/2" metal boxes
Keep in mind that electrical wiring is not a project for novices. You should have an understanding of basic wiring techniques, how to determine circuit size and evaluate loads, and know safety precautions. And always check with your local building department to get a permit and an inspection for all work you do.
For safety, exposed electrical wiring (in the garage, basement and outdoors) must be protected by sturdy tubing. We chose 1/2-in. EMT metal conduit for this project because it’s easy to bend and assemble (and take apart if you make a mistake!). PVC conduit is another good option, but it differs in that you glue the joints.
Plan Your Run
The first step is to find your power source. We tapped in to a 15-amp garage outlet receptacle to power the “light-duty” workbench area. If you copy this project and operate power-hungry tools such as circular or table saws, you may need to tap in to or run a new 20-amp circuit. Check the circuit breaker in the main electrical panel to determine the circuit size. If you’re uncertain about circuit sizing, consult a licensed electrician.
Next, sketch the conduit route from your power source to the new electrical box locations and note the length of the run and all the boxes, connectors and wire you need. Our materials included 1/2-in. EMT conduit (10 ft. long, $1.25), 4 x 4 x 1-1/2 in. metal boxes (which hold two receptacles), 4-in. square raised covers, one 1/2-in. offset setscrew connector ($1.25) for each conduit/box connection, plus 1/2-in. couplings (to join two pieces of conduit in longer runs—not shown), conduit straps, a 15-amp switch, receptacles and 14-gauge THHN wiring (the type of wire to run inside the conduit). If you get power from a 20-amp circuit, use only 12-gauge THHN wire. These items are at home centers and full-service hardware stores.
Simple Tools
A 1/2-in. conduit bender is the only specialty tool you need to bend 10-ft. sections of 1/2-in. EMT conduit. You’ll spend $9 to $12 for the head and $2 to $3 for a 3/4 x 24-in. water pipe, which serves as the handle and screws into the bender head. Along with that, you need basic hand tools, a hacksaw and a drill with a 1/4-in. masonry bit ($2). And you may need a fish tape ($30) to pull wire if you have long conduit runs with multiple bends.
Bending Basics
We’ll only show how to make 90-degree bends, since they’re the easiest and most often used. Another common bend is an offset, which is a difficult two-part bend that positions the conduit slightly off the wall to connect straight into electrical boxes. We chose to use offset setscrew connectors to simplify this task.
Bending conduit isn’t difficult. But you may not get perfect bends on the first try, so buy an extra 10-ft. length just in case. If you don’t want to bend conduit, you can buy gradual “90-degree sweep bends” or “90-degree square corner elbow fittings.” However, your project won’t look as professional because of the numerous connectors, and the extra joints make it harder to push or pull wire.
Power-Hungry Tools
If you plan to power any tools, be aware that a common 15-amp circuit may overload and trip if any of the following tools are run simultaneously (especially if your shop lights are on too):
Miter saw | 13 to 15 amps |
Circular saw | 13 to 15 amps |
Router | 9 to 11 amps |
Belt sander | 6 to 12 amps |
We recommend a maximum connected load (lights and other permanently plugged in devices) and operating load (tools and other temporarily running devices) of 1,440 watts (12 amps) for a 15-amp circuit and 1,920 watts (16 amps) for a 20-amp circuit.
Start at the Power Source
After you’ve chosen the electrical box to tie in to, turn off the circuit breaker or unscrew the fuse that protects the circuit.
Some electrical boxes may contain wires from more than one circuit. Before doing any work, test all the wires with a non-contact voltage sniffer ($12 at hardware stores and home centers) to make sure they’re “dead.”
Next, remove the existing receptacle and box from the stud. Now position (not attach) a 4 x 4 x 1-1/2 in. metal electrical box on the drywall surface, slightly above or below the existing opening so you can pull at least 1/4 in. of the cable sheathing through the back of the box. Cut the drywall and shift the box if necessary to get more sheathed cable inside the box. You have to patch the drywall anyway, before you screw the new box to the wall.
Bending Conduit
For 90-degree bends in 1/2-in. conduit, the rule is to subtract 5 in. from the connector-to-wall measurement. If the total distance is 33 in., mark the conduit at 28 in. Be sure to measure to the inside of the offset connector where the conduit actually seats.
Bend conduit by positioning it in the bender so your distance mark on the conduit lines up with the bender arrow. Apply pressure with your foot and hand to bend the end of the conduit straight up. Then check the angle with a magnetic torpedo level (or with the bubble level built into some bender heads) and adjust the bend until you get 90 degrees.When measuring for the vertical rise, measure the height difference between the two boxes. Again, take that distance and subtract 5 in. Then add 3/4 in. to account for the thickness of the conduit in the first bend. Attach Boxes to MasonryAfter leveling the conduit and marking the location for Box 2, be sure to smooth all cut edges with a pliers. Now drill the two holes for plastic anchors and a clearance hole for the ground screw. Attach the box to the concrete with plastic anchors and panhead screws.
Repeat this process to attach all other boxes, as well as the straps that hold the conduit to the masonry. When using 1/2-in. EMT conduit, position straps within 3 ft. of each box and within 10 ft. thereafter. Once you’ve installed the conduit and rotated the offsets so the conduit rests against the wall, tighten the offset connector locknuts with a sharp rap of a hammer on a screwdriver.
When running wire short distances with few bends, such as between Boxes 2 and 3, and 3 and 4, you can simply tape the two wire ends together and push them through the conduit. For longer distances, or runs that have two or more bends, run a fish tape through the conduit and tape the wires to it.
CAUTION:
If you have aluminum wiring, leave it alone. Call in a licensed pro who’s certified to work with it. This wiring is dull gray, not the dull orange that’s characteristic of copper.
Garage receptacles must be GFCI protected. Before wiring the GFCI receptacle into Box 1, bend or break off the top and bottom ears. Repeat this step with all receptacles so they fit inside the metal box as well as screw to the 4-in. square cover (that is raised 1/2 in.). Now connect the GFCI receptacle as shown, followed by the other boxes. Then screw all receptacles to the covers and attach the covers to the boxes.
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