Ask This Old House master electrician Heath Eastman explains the purpose of a ground wire and then grounds an outlet for a homeowner.
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Time: 3-4 hours
Skill Level: Professional Only
NM cable [https://amzn.to/2Rn8piJ]
Arc-fault breaker [https://amzn.to/2JS45ns]
GFCI receptacle or grounded receptacle [https://amzn.to/2xWfHTA]
Electrical staples [https://amzn.to/2UUAksr]
Steps for Replacing Two-Prong Electrical Outlets:
1. Heath starts by explaining the purpose of a ground wire:
a. To complete an electric circuit, power must be sent from the panel, through the hot wire, and back through the neutral wire. Under normal operating circumstances, the electric devices in a home should work without issue.
b. If a device faults, meaning that the current in the circuit strays from the path for a variety of circumstances (water near exposed wires, two wires touching, etc.), that current will go wherever is easiest, which can create a shock hazard.
c. A ground wire is a bare piece of copper that goes into the jacket of wiring with the hot and neutral wires. Due to its extreme conductivity, excess current from a fault will naturally travel on the bare copper and cause the breaker to trip.
d. While the lack of a ground wire won’t prevent an electrical device from working properly, the ground wire is an important safety device that is now part of the electrical code.
2. In most cases, grounding a receptacle means running new wiring with a ground wire in it. Start by cutting power to the main electrical panel.
3. Run the NM cable from the panel to the location of the outlet. This process could result in a wide variety of obstacles, including getting the cable through floors and behind walls, or in this case, running the cable across basement joists and stapling them in place with electrical staples and a hammer. The ease of running the wire will determine the overall cost of the job.
4. Next, wire the receptacle. If an old two-prong receptacle is still in use, that will need to be replaced with either a three-prong receptacle (in living spaces) or a ground fault circuit interrupting receptacle (in bathrooms, kitchens and basements), depending on its location. Wiring will usually require a pair of pliers and a screw driver to secure the wires to the receptacle.
5. Back at the panel, wire the new wiring to a circuit breaker. In this case, Heath used an arc fault breaker and added it to the panel. The hot and neutral wire to the breaker, the neutral pigtails to the neutral bar, and the ground wire ties into the grounding bar. These wires can be secured with a screwdriver.
6. Turn the power back on.
Any work that involves working on the electrical panel can be dangerous and should only be done by a licensed professional.
In this scenario, Heath found that none of the surrounding receptacles or their wiring were to code, so he removed and replaced them with a 12-2 NM cable and a single GFCI outlet. These materials can be found at any home center or electrical supply store.
Expert assistance with this segment was provided by Eaton and Eastman Electric (http://www.eatonandeastmanelectric.com/).
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How to Ground a Two-Prong Electrical Outlet | Ask This Old House