Working with armored cable

MATERIALS: BX or MC cable, protective bushings

TOOLS: Side-cutting pliers, screwdriver, hammer, channel-joint pliers, armored cable cutter

Armored cable is the middle ground between NM and conduit. It is easier to install than conduit and less flexible than NM. It protects wires better than NM but not as well as conduit. There are two types of armored cable. BX cable has no ground wire, the sheathing itself providing the ground. MC cable has a green-insulated grounding wire and is often required by code. Some codes call for armored cable instead of NM. Others require NM or conduit where the cable is exposed. Run armored cable inside walls, and protect it from nails as you would NM cable.

1 TWIST THE CABLE. Grasp the cable firmly on each side of the spot you want to cut. Twist the waste end clockwise until the armor comes apart far enough for you to slip in cutters. If you have trouble doing this with your bare hands, use two pliers. SNIP AND REMOVE THE ARMOR. Cut through one rib of the armor with a pair of side-cutting pliers. Slide the waste arm off the wires, keeping your hands clear of sharp edges.

2 TRIM SHARP ENDS. Remove paper wrapping and plastic strips. Leave the thin metal bonding strip alone. Use side-cutting pliers to snip away pointed ends of sheathing that could nick wire insulation. SLIP ON THE BUSHING. Slip a bushing over the wires. Slide it down into the armor so the bushing protects the wires from the sharp edges of the armor. If there is a bonding strip, ask your inspector what to do with it. Most inspectors want you to cut it to about 2 inches and wrap it over the bushing and around the armor, helping to ensure conductive contact between the armor and the box.

3 ATTACH THE CLAMP. Remove the locknut from an armored cable clamp. Slide the clamp down over the bushing as far as it will go, and tighten the setscrew. Double-check to make sure that none of the wires are in danger of being nicked by the armor. CONNECT TO THE BOX. Remove a knockout slug from a metal box and poke the connector into the hole. Slide the locknut over the wires and tighten it onto the cable clamp. Use a hammer and screwdriver to tap the locknut tight.

Running conduit

MATERIALS: Conduit and fittings, wire, PVC cement, lubricant

TOOLS: Screwdriver, lineman’s pliers, hacksaw, conduit reamer, fish tape

Conduit is the most durable product for running wire. It’s more expensive and time-consuming to install than cable, but it is no longer necessary to learn how to bend conduit. Ready-made parts make installation easier than ever. Use conduit on unfinished walls and ceilings where wiring will be exposed. Use electrical metallic tubing (EMT), or thin wall conduit, for most indoor installations. Use thicker intermediate metal conduit (IMC) above ground outdoors. Use plastic rigid nonmetallic conduit (PVC) for underground applications.

ASSEMBLING THE PARTS. Take a rough drawing of your installation to a home center or electrical supply store. Ask a salesperson to help you gather all the pieces you need. Generally use 1/2-inch conduit for up to five #12 wires or six #14 wires, and 3/4-inch conduit for more wires. (Larger conduit will make pulling easier, so consider buying 3/4 inch in every case.) Use a sweep to turn most corners. Use setscrew couplings and elbows for indoor installations (you'll have to use compression fittings outdoors). At every four bends install a box or a pulling elbow. If the conduit and the box are installed flush against a wall, you'll need an offset fitting.

Greenfield conduit - Greenfield. Also called flexible metal conduit, Greenfield is essentially armored cable without the wires. It is expensive, so use it sparingly for places where rigid conduit would be difficult to install.

PVC conduit - PVC conduit. In many areas PVC is acceptable for indoor and outdoor installations. Cut it with a backsaw or hacksaw and a miter box. Glue the pieces together using PVC cement approved by an inspector.

1 MEASURE AND CUT. Install the boxes first, then cut conduit to fit between them. At a corner, have a helper hold a sweep in place while you mark the conduit for cutting. Use a hacksaw with a fine-tooth blade to cut.

2 REMOVE BURRS. Ream out all burrs with a conduit reamer so the wires can slide smoothly past joints without damaging the sheathing. Any tubing that carries electrical wires must be free from burrs and sharp edges that could damage the wire while it’s being pulled.

3 RUN FISH TAPE AND ATTACH THE WIRES. Feed the fish tape through the conduit in the opposite direction from which you will pull the wires. Trim the insulation in a stair-step fashion (staggered exposure of wire) to make the wire easier to pull. Poke the wire ends through the fish tape's loop and bend them over. Wrap firmly and neatly with electrician's tape so the joint will not bind when it goes through a sweep.

4 SQUIRT LUBRICANT. To make pulling easier on long runs, pour a bit of pulling lubricant on the wires. (Avoid using substitute lubricants like dishwashing liquid or hand soap. Some can dangerously degrade wire insulation overtime.)

5 PULL THE WIRES. Have someone feed the wires through one end while you pull the fish tape on the other end. Pull with steady pressure and keep the wires parallel to avoid twists that will jam in the conduit. Try to keep the wires moving, rather than starting and stopping. If they get stuck, back up a few inches to gain a running start.

INSTALL PULLING ELBOWS - If the conduit will make more than three turns between boxes, install a pulling elbow to make fishing easier. Don't splice wires here; just use the opening to pull the wires through.

Adding a circuit

MATERIALS: Cable and clamp, new circuit breaker

TOOLS: Hammer, screwdriver, lineman’s pliers, combination stripper

If you’re uncomfortable with the prospect of adding a new circuit on your own, get some advice from your home center or hire a pro.

FIRE PROTECTION - The NEC now requires the use of Arc Fault Circuit Interrupters (AFCI) for bedroom circuits. AFCIs provide greater fire protection than a regular breaker. Regular breakers trip for overloads and short circuits. AFCIs offer protection when arcing occurs because of frayed and overheated cords or from faulty wire insulation.

The physical work of installing a new electrical circuit is simple and calls for no special skills. Most of the work is completed outside the service panel. To get a breaker that will fit in your panel, jot down the brand and model number or bring a sample breaker to the store. First determine whether your service panel can accommodate a new breaker, and then plan a circuit that will not be overloaded. If the circuit will be in a bath or along a kitchen countertop, consider installing a GFCI breaker, so that you won’t have to install individual GFCI outlets. Install the new boxes. Run cable from the boxes back to the service panel. Electricians call this practice a “home run.” Hook up the devices and fixtures. Now you’re ready to energize the new circuit by installing a new breaker and connecting the wires to it. Always buy breakers made by the same company that made the boxes they’ll go in.

BREAKER OPTIONS - If the service panel has room, install full-size, single-pole breakers. If you're out of space, see if your panel can accommodate half-size or skinny breakers, or tandem breakers. In some panels, these breakers only fit in slots near the bottom. You'll need double-pole breakers or a wafer breaker for 240-volt circuits. A quad breaker can supply two 240-volt circuits. Your building code limits the number of breakers that can be installed. If you add too many, an inspector will require you to put in a new panel or a subpanel.

1 SHUT OFF MAIN POWER. Work during the daytime and have a reliable flashlight on hand. Turn off the main circuit breaker. All the wires and circuit breakers in the panel are now de-energized except for the thick wires that come from the outside and connect to the main breaker: Do not touch them.

2 REMOVE A KNOCKOUT. Remove the service panel cover. Remove a knockout slug from the side of the service panel and install a cable clamp. Also remove a knockout tab from the panel cover. (For a double-pole breaker, remove two knockouts.)

3 CLAMP THE CABLE. Determine how far the wires must travel to reach the breaker and the neutral bus bar. To avoid tangles, plan a path around the box’s outside perimeter. Strip about a foot more sheathing than you think you will need. Thread the wires through the clamp and secure the cable. Don't over tighten.

4 CONNECT THE NEUTRAL WIRE. Run the neutral wire toward an open terminal in the neutral bus bar, bending the wire carefully so it will easily fit behind the panel cover. Cut the wire to length and strip off about Vi inch of insulation. Poke the end into the terminal and tighten the setscrew. Connect the ground wire to the ground bar (or neutral bus bar if there is no ground bar).

5 WIRE THE NEW BREAKER. Run the hot wire, bending it carefully so it will easily fit behind the panel cover. Cut the wire to length. Strip off 1/2 inch of insulation. Poke the wire into the new breaker terminal. If bare wire is visible, remove the wire, snip it a little shorter, and reinsert it. Tighten the setscrew.

6 SNAP THE BREAKER INTO PUCE. Make sure the breaker is in the off position, and then slip one side of the breaker under a tab to the right or left of the hot bus bar. Push the other side onto the bus bar until the new breaker is flush with the other breakers. (Some brands of breakers may require a slightly different installation method; check the instructions.) Restore power, turn on the breaker, and try the switches or receptacles to see if they're getting power.

7 INSTALLING DOUBLE-POLE BREAKERS. Check to see if you have the two free spots you'll need for a 240-volt breaker. (A tandem breaker takes up only one spot and can be substituted as long as there are two lugs for it.) Shut off the power. Connect the black and red wires to the breaker terminals. Connect the white wire to the neutral bus bar and the ground wire to the ground bar (or neutral bus bar if there is no ground bar).

Log in to comment