There are several types of conduit to choose from when wiring a house--EMT (Electrical Metallic Tubing) or "Thin-wall," RMC (Rigid Metal Conduit,) PVC Plastic, or FMC (Flexible Metal Conduit). When wiring a house during construction, any of these conduit system will work equally well. The best conduit to use when upgrading an electrical system in a finished structure is FMC because it can be fished through walls, ceilings, and floor just as cable can with minimal disruption to the structure's finish.
- Skill level:
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Things you need
- National Electric Code, 2008 Revision
- Flexible metal conduit
- Support straps
- FMC connectors
- Metal device boxes, "old work"
- Metal J-boxes (junction boxes) with metal covers, "old work"
- Metal lighting outlet boxes, "old work"
- Building wire (red, black, green and white)
- Fish tape (wire pulling tape)
- Electronic stud finder
- Measuring tape
- 3/8-inch battery powered drill/driver
- Spade bits
- Jab saw or portable jigsaw
- Diagonal pliers/wire cutters
- Lineman's pliers/electrician's pliers
- Needle nose pliers
- FMC cutter
- Flat pry bar
- Wood chisels
- Metal nail plates
- Nail set
Layout the location of all device boxes, the boxes that will house receptacle outlets and light switches, and all lighting outlet boxes on graph paper. Be professional here because the city engineer is going to want to see this drawing when you apply for the electrical permit.
Layout the location of the receptacle boxes so no point along the floor line is more than six feet from an outlet. Position the first box six feet from a door and then position the rest at 12-foot intervals. A duplex receptacle is considered two receptacles by the Code and covers a wall space of six feet to each side of its location. Any wall space two feet or more in width requires a receptacle.
Mark the intended height of all boxes on the layout. Standard mounting heights above the finished floors are: 46 inches for switches, 12 inches for receptacles, and 66 inches for wall-mounted lighting outlets.
Mark on the drawing the size of the FMC being used, the number of conductors in each section and their size.
Order materials and wait for permit to arrive before beginning actual work.
Remove the baseboards and cut a two-inch wide channel in the wall finish where conduit will be located. Use caution here because you don't want to cut through the wall studs. Use a wood chisel to remove the finished wall over the studs.
Using the portable jigsaw and a chisel, make a ¾-inch deep by one-inch wide notch in each stud face. This is the easiest way to run conduit while doing minimal damage to the wall finish.
Using one of the device boxes as a marking guide, draw around it with a pencil or fine tip marker and cut out the openings for all receptacle and switch boxes. Use the electronic stud detector to make sure you're not cutting into a stud or cutting so close to the stud that the mounting wings will not have enough room to open.
Lay in the flexible conduit. A helper really comes in handy here to guide the flex through the device box opening so you don't accidentally damage the wall surface. Once the conduit is in place, cover the notches with a "nailing plate."
Pull the required number of conductors through each section of flexible conduit before attaching the conduit to the boxes. Allow enough wire at each end so that there will be at least six inches of free conductor in each box.
Secure the flex to the metal boxes using a flex connector.
Slip the boxes into the wall and draw the wings up against the inside of the wall by turning the screws in a clockwise direction, securing the box in place.
Call for the rough-in inspection.
Replace baseboards. Install devices. Call for final inspection.
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