How to Convert 2-Wire House Wiring to 3-Wire Ground

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Homes more than 30 years old may have a number of wiring issues caused by the changing National Electrical Code. Tips that a house may require electrical upgrades includes the presence of older service panels with fuses, and the presence of two-prong electrical outlets. The older, fabric-covered, nonmetallic cable may not have a ground wire inside and will need to be replaced. Current electrical code requires that all electrical outlets be properly grounded. To do this, houses with older two-wire cable need to be upgraded with three-wire ground circuits.

Things You'll Need

  • Panel service tag
  • Screwdriver
  • Electrical pliers
  • Cable ripper
  • Nonmetallic three wire cable rated for the circuit
  • Electrical staples
  • Three-pronged outlets
  • Outlet tester
  • Switch the main circuit breaker to the "Off" position. If the main panel has a fuse, remove the main fuse blocks. Place a service tag on the circuit breaker to warn others not to turn the power on. Loosen the fasteners on the panel box and remove the panel cover. Set the panel cover aside. Unscrew the fuse to the circuit.

  • Loosen the black wire lug using a screwdriver. Loosen the white neutral wire lug from the neutral bus using a screwdriver. Loosen the cable connector clamp holding the wire to the panel by turning the screws counterclockwise. Pull the old nonmetallic cable from the panel. Loosen the outlet covers and outlets using a screwdriver. Remove the double-pronged outlet. Loosen the cable clamp on the receptacle box. Remove the old electrical wire and any electrical staples.

  • Insert the new nonmetallic wire into the main panel through the cable connector. Insert enough wire to reach the load lug terminal, the neutral bus bar and the grounding bar. Use an electrical staple to fasten the new wire within 8 inches of the panel. Tighten the cable connector turning a screwdriver clockwise. Strip the nonmetallic plastic cover from the cable using a cable ripper and electrical pliers, taking care not to damage the wire insulation inside.

  • Strip 1/2 inch of insulation off the black load wire and white neutral wires. Insert the black wire into the load lug and the white wire into the neutral bus. Tighten the lug screws with a screwdriver. Insert the bare ground wire into the grounding bus and tighten the lug screw with a screwdriver. Insert the cover screws into the panel cover and tighten them with a screwdriver.

  • Thread the rigid wire fish tape to the electrical panel from receptacle box and twist the new electrical cable to the end of the fish tape. Pull the fish tape with the wire to the receptacle box. Fasten the new electrical cable with an electrical staple within 8 inches of the electrical outlet and every 4 1/2 feet along the circuit.

  • Insert the electrical cable into the receptacle box through the cable clamp. Remove six inches of external insulation from the cable using the cable ripper and electrical pliers. Thread the three wires through the cable clamp in the outlet box. Tighten the cable clamp screws using a screwdriver. Strip 1/2 inch of insulation from the black wire and from the white wire.

  • Bend each of the wire ends into a c shape using the electrical pliers. Unwrap a new three-pronged outlet. Tighten the black load wire onto the brass colored screw, the white neutral wire onto the dulled screw and the bare ground wire onto the green screw. Push the outlet into the receptacle box and tighten the retaining screws with a screwdriver. Insert the outlet cover plate screw into the outlet cover and tighten with a screwdriver.

  • Remove the service tag from the panel. Turn the circuit breaker to the "On" position, or plug the main fuse back into the outlet. Screw the circuit fuse back into the fuse holder. Plug an outlet tester into an outlet on the new circuit to check that the ground, load and neutral sides of the circuit work and are properly connected.

Tips & Warnings

  • Old wiring becomes brittle with age and will crack if bent. When working with older wiring, check the service panel to ensure the amperage is adequate for the house. Some older houses have 30-amp service that must be upgraded to 100 amps. Check with the electrical inspector when applying for a building permit if this is the case.
  • Never use the white neutral wire as an improvised ground. This practice was done in some locations and may result in electrocution. Never touch the service lugs in the main panel. They remain energized after the circuit breaker or fuse is removed.

References

  • "National Electrical Code Handbook, 25th Ed."; Brian J. McPartland, Joseph F. McPartland; 2005
  • "The Complete Guide To Home Wiring"; Andrew Karre; 2005
  • "The Complete Idiot's Guide to Remodeling your Home"; Terry Meany; 1999
  • Photo Credit Light Switch and Outlet image by Towards Ithaca from Fotolia.com
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