How to Wire a Small House

You can tackle a home wiring project yourself.

Install the appropriate electrical boxes wherever your cable is cut. They protect exposed wire.Install the appropriate electrical boxes wherever your cable is cut. They protect exposed wire.
Doing so will save you money, but before beginning any large-scale home wiring project, you may want to consult with your electric utility and a licensed electrician to be sure you have all the information you need to do it right.

Map out the exact locations in the house that will need electrical outlets and wall switches.

Check local and state electrical codes for single-family residences to determine any requirements for the height of outlets from the ground, the distances between outlets, the location of the electric service panel and any other requirements relevant to your project.

Make an amperage estimate by anticipating the appliances, devices or lights that will need to be powered simultaneously on a given outlet or switch. Add up their amperage values to determine the total for that outlet or switch.

Determine which outlets and switches should be connected in a circuit. Look for outlets and switches in close proximity to one another. Add up their maximum current needs until you are at about 15 to 17 amps. This is a good number to aim for because regular, modern home electrical circuits typically carry 20 amps of current before overloading and tripping the circuit breaker. To save yourself work and money, you should connect as many outlets and switches as possible to a single circuit without risking an overload.

Map out the path your regular electrical circuits will take. Circuits usually travel straight up from the main service panel, above the ceiling or sometimes behind the wall and then straight down behind the wall to the location of the outlet or switch.

Map special circuits for major appliances such as electric ovens and clothes dryers. These appliances each tend to require their own dedicated circuit and often run on 240 volts, which will require double wiring---basically just two 120-volt circuits running side by side.

Plan special circuits to supply outdoor outlets. These should be separate from any indoor outlets or switches and may be either 120 or 240 volts, depending on your needs.

Install the main service panel. You may want to consider having an electrician perform this step for you. Despite its highly specialized nature, it's really just a big box. Mount it securely to the wall near where your feeder lines will enter the house. The service panel should be rated to supply between 200 and 400 amps, depending on your needs. You can purchase one from any good hardware store or electrical supply warehouse.

Install 20-amp circuit breakers into the main service panel. They will fit neatly into the slots on the service panel and are usually secured in some fashion. Do not connect the feeder lines to the main breaker until the end of the entire project, which guarantees that the rest of your wiring work will carry no risk of electrical shock. As you carry out the installation, make sure that all live, neutral and ground terminals on each circuit breaker are correctly and securely connected to the corresponding hot, neutral and ground buses on the main service panel. You need not fill up all the circuit breaker slots on the panel.

Run your regular circuits throughout the house using standard 12-gauge nonmetallic sheathed electric cable. In open areas, such as the attic, secure the cable to the beams along which it is running with fasteners. Do not damage the cable.

Lay your 240-volt circuits in the same fashion, running two electric cables side-by-side instead of just one.

Install electrical junction boxes wherever your circuits drop down to serve an outlet or switch. Cut the sheathed cable and strip the individual wires at both ends. Do the same with one end of a second cable that will run down from the main cable to the outlet or switch. You will end up with three hot wire ends, three neutrals and three grounds, all in the same place. Run these wires into the junction box, making sure that the stripped portions are located entirely within the junction box. Braid the three hots together and cap them with a black-colored wire cap. Do the same with the other wires, making sure each wire goes into a cap matching its color.

Install your outlet and switch boxes into the walls. Run the cable into the box, strip the ends of the wires and connect the hot, neutral and ground wires to their respective terminals on the outlet or switch. Do the same with any special outlets for major appliances.

Double check all your work. In particular, look for accidental damage to the wires and loose connections in the boxes.

Hire a licensed electrician to inspect and certify your work. Make any changes the electrician requires.

Ask your electric utility to disconnect your power for a specified amount of time so that you can connect your main service panel to the incoming main power line. After the power is off, test it with a multimeter to be sure, and then make the connection. You may want to have your electrician handle this step.

Turn on the main circuit breaker on your service panel, once your electric company has restored your power, and individually turn on one circuit at a time, testing it for functionality.

Things You Will Need

  • Electric service panel, rated 200 to 400 amps
  • Circuit breakers, 20-amp
  • Nonmetallic sheathed electric cable, 12-gauge with 2 or 3 service wires and ground
  • Electrical wall outlet boxes, standard and special
  • Electrical wall switch boxes and switches as needed
  • Electrical junction boxes
  • Ladder
  • Multimeter
  • Screwdriver
  • Screws
  • Drill
  • Wrench
  • Hammer
  • Nails
  • Fasteners
  • Wire strippers
  • Wire cutters
  • Wire caps in black, white, green, red, yellow

Tip

  • If your devices do not list amperage values, you can divide their wattage values by the house voltage, 120 volts or 240 volts, depending on the device. This will yield an amperage.

Warning

  • Never work on live circuits.

About the Author

Josh Fredman is a freelance pen-for-hire and Web developer living in Seattle. He attended the University of Washington, studying engineering, and worked in logistics, health care and newspapers before deciding to go to work for himself.