How to Wire an Isolated Ground Electrical Outlet

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An isolated-ground electrical receptacle provides additional grounding protection for computers and electronic equipment because its grounding path is wired directly to the main grounding bar for the entire house. This means there is less electrical "noise" interfering with equipment plugged into the receptacle, because it does not share a grounding path with the rest of the house's electrical system. The receptacle itself looks like a regular three-prong electrical outlet but is usually made of orange plastic and has a triangle marked on its face. Replacing a standard outlet with an isolated-ground one may not be an entirely simple task, but it's an excellent do-it-yourself project for those with home wiring experience.

Things You'll Need

  • 14/3 NM copper electrical cable
  • Single-pole 15A circuit breaker
  • Isolated-ground receptacle
  • Screwdriver
  • Fish tape
  • Circuit tester
  • Wire cutters
  • Wire stripper
  • Plastic wire connectors
  • Electrician's pliers
  • Cable clamp
  • Turn off the power to the old outlet at the breaker box. Remove the outlet's cover plate and use the circuit tester to make sure the power is switched off.

  • Unscrew the two screws holding the old outlet in its outlet box and gently pull it out of the box. Disconnect the outlet from its cable by loosening its terminal screws and removing the wires wrapped around each of them. Cap the bare ends of the old wires by twisting a plastic wire connector onto each one. Push them to the back of the outlet box.

  • Run the cable for the new outlet from the outlet box directly to the breaker box, using fish tape to guide the cable through the wall if needed. Leave 10 inches of cable hanging out of the outlet box at the receptacle end.

  • Strip the sheathing off the cable to expose the four wires inside: black, white, red, and bare copper. Loosen the grounding screw inside the outlet box, then use the pliers to wrap the bare copper wire around the screw. Tighten the screw.

  • Connect the new cable to the isolated-ground receptacle. Use the pliers to wrap the red wire around the receptacle's grounding screw, the black wire around its hot terminal (a brass or black screw), and the white wire around its neutral terminal (a silver screw). Tighten all the terminal screws.

  • Push the wires into the box. Attach the receptacle to the box by tightening its two mounting screws with the screwdriver. Attach the outlet cover plate to the outlet box with the screwdriver.

  • At the breaker box, switch off the main breaker, which will turn off power to all the circuits in the box. Use the circuit tester to make sure no electricity is flowing to the circuit breakers.

  • Run the cable into the box through one of the knockout holes in its side, leaving a length of about 2 feet of the cable inside the box. Secure the cable to the box using the cable clamp, and strip the sheathing off the end of the cable.

  • Attach the cable wire to the appropriate terminals inside the box using the screwdriver. The box contains two long bars with wires from the other circuits connected to them with screws: the neutral bar (white wires) and the grounding bar (bare copper wires). Use the screwdriver to connect the white wire to the neutral bar of the breaker box, the bare copper wire to the grounding bar, and the red wire to either the neutral bar or the ground bar.

  • Connect the black wire to the terminal on the new 15A circuit breaker and tighten its screw. Push the breaker into an open slot in the breaker box until it snaps in place.

  • Turn the main breaker back on and switch the the new circuit breaker switch to "on." Make sure the new outlet is working by checking it for electrical current using the circuit tester.

Tips & Warnings

  • Check your local electrical codes before you begin any home wiring project and obtain any permits you may need.
  • Never attempt any home wiring project without first turning off the electricity to the circuit at the breaker box.

References

  • "Complete Guide to Home Wiring;" Editors of Creative Publishing; 2005
  • Photo Credit electrical outlet image by Mat Hayward from Fotolia.com
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