Electrical Outlet wire connections (C) D FriedmanElectrical Outlet Ground Wire Connections
How to connect the grounding conductor at an electrical plug outlet or wall receptacle
     


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How to connect the ground wires at an electrical receptacle:

Here we give the proper ground wire connections when hooking up an electrical receptacle (wall plug or "outlet")?

We describe connecting the incoming circuit grounding conductor wire, receptacle ground screw, and the electrical box (if metal boxes are used).

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Ground Wiring Details when Installing an Electrical Receptacle

Color coding of wires to properly connect an electrical outlet (C) Carson Dunlop AssociatesThe illustration at left shows the typical wiring of an electrical outlet or "receptacle", courtesy of Carson Dunlop Associates.

You can see the incoming ground wire aimed towards its connection point - the green screw on the electrical receptacle. But additional grounding connections are often required as well - as we will detail here.

Watch out: Electrical components in a building can easily cause an electrical shock, burn, or even death.

Even when a hot line switch is off, one terminal on the switch is still connected to the power source.

Before doing any work on the switch, the power source must be turned off by setting a circuit breaker to OFF or removing a fuse. See SAFETY for ELECTRICAL INSPECTORS and ELECTRICAL WIRING BOOKS & GUIDES

Connect the Ground Wires to the Receptacle

Electrical wire 14-2 with ground (C) D Friedman

The bare ground wire - this wire, visible in our photo as the un-insulated copper wire seen between the white (top) and black (bottom) wires, connects to the green ground screw usually found on the bottom of the electrical receptacle (photo at left).

What if there is no ground wire in the circuit?

If you are connecting an electrical receptacle to an older circuit that just provides hot and neutral wires, that is, no ground, and assuming you're not going to re-wire the circuit to provide a proper ground, there is no ground wire to hook-up. In this case you must use a type of electrical receptacle that does not include the third opening for the grounding prong on the wall plug.

Details are at CONNECTION for 2-WIRE RECEPTACLE CIRCUITS - no ground

Electrical Outlet wire connections (C) D FriedmanProper grounding connections for an electrical receptacle

The electrical receptacle must be properly connected to the building grounding system - not shown in our sketch.

That connection is made from the ground screw on the receptacle to the grounding conductor (usually bare copper) in the wire leading back to the electrical panel where in that location it is connected to a grounding bus and from that bus to the building grounding system, one or more earth-driven electrodes or their equivalent.

The incoming ground wire is connected to the ground terminal on the electrical receptacle (usually a green screw such as shown in our photo at left).

If the junction box is metal (not plastic) the ground wire is also connected to the metal junction box itself, usually by a special green screw that connects to a tapped threaded hole on the junction box back side, or by a grounding clip that secures the ground wire to the edge of the metal box.

If there is more than one feeder wire entering the electrical junction box then all of the grounds are connected together as well as being connected to the ground screw on the receptacle itself.

Ground connection in junction box (C) D Friedman Color coding of wires to properly connect an electrical outlet (C) Carson Dunlop Associates

If the junction box is plastic, you're done.

If the junction box is metal (photo above right) then a ground wire is also connected to the metal box using an approved grounding screw or clamp device to tie the wire end to the box. Most metal electrical boxes have a threaded hole intended for use as a connection point for the ground wire connecting screw, as illustrated in our photograph (left).

In sum, all of the grounds are tied together in the box: the incoming ground, outgoing ground, and ground wires to each of the electrical receptacles and if it's metal, to the junction box itself.

Electrical receptacle mounting strap and screw are not a ground (C) D Friedman

Watch out: Don't rely on the connection between the electrical outlet's steel mounting strap and the steel screw openings of the junction box to provide the ground connection. That's not a legal ground and it's unreliable

Use the a ground wire and ground screw on the receptacle itself to be sure that this important safety feature is correctly installed.

See ELECTRICAL GROUND SYSTEM INSPECTION

and Definition of Electrical Ground Terms.

It's easy for the receptacle mounting screws to be deliberately left loose or to work loose - making that ground connection unreliable. Use a ground wire, as the connection through the receptacle mount screws is simply not reliable.

Watch out: mis-wired electrical receptacles are dangerous. This article series describes how to choose, locate, and wire an electrical receptacle in a home.

Reader Question: how is an electrical outlet wired to the electrical panel?

how do wire the outlet plug to the electrical panel - Anon

Reply:

Anon, the electrical circuit that powers an "outlet plug" or receptacle is connected, usually through building walls, ceilings, or floors, from the first receptacle in the particular series back to a fuse or circuit breaker connection in the electrical panel. The fuse or circuit breaker, by its connecting mount in the electrical panel, receives electrical power from the income electrical service.

Ultimately in the electrical box where the electrical receptacle ("wall plug" or "wall outlet" in common speech) is mounted,

  1. The incoming black or hot wire in the electrical box is connected to the bronze or brass colored screw on the receptacle; the other end of the hot wire is connected to the circuit breaker or fuse connector screw in the electrical panel.
  2. The incoming white or neutral wire in the electrical box is connected to the white or silver colored screw on the receptacle and the other end of the neutral wire connects to the neutral bus in the electrical panel.
  3. The incoming ground wire or grounding conductor in the electrical box connects to the green ground screw on the receptacle and also, by extension or pigtailing, to the junction box if the electrical box is metal not plastic. In the electrical panel the other end of the grounding conductor connects to a ground bus bar that in turn is connected to earth, usually by grounding electrodes at the building exterior or in some jurisdictions to a buried metal water pipe.

Reader Question: what do I do with the screws to which no wire is connected on a conventional "plug" (wall receptacle)?

At the end of a circuit, I'm only using 2 of the 4 screws on a conventional plug. What should I do with the 2 unused screws? Should they be screwed all the way in? Or left partially unscrewed? Or does it matter? - Chris Rasko 7/8/12

Reply:

Chris:

regarding the un-used screw terminals on an electrical receptacle, you should simply screw them all the way in and leave them alone. Don't remove the screws - it's not necessary, they are deliberately hard to remove completely, and they could be needed in some future wiring change.

 

Continue reading at HEIGHT above FLOOR for OUTLETS or select a topic from the More Reading links shown below.

If you are wiring a 2-wire electrical circuit that has no ground wire, also see CONNECTION for 2-WIRE RECEPTACLE CIRCUITS for proper wiring details.

Or see CONNECTION DETAILS - where to connect black, white, red, green, ground wires.

Suggested citation for this web page

GROUND WIRE CONNECTIONS at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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