Question? Just ask us!
Free Encyclopedia of Building & Environmental Inspection, Testing, Diagnosis, Repair
InspectAPedia ® Home
ELECTRICAL INSPECTION, DIAGNOSIS, REPAIR
ACCURACY vs PRECISION of MEASUREMENTS
AFCIs ARC FAULT CIRCUIT INTERRUPTERS
ALUMINUM SECs & WIRING
ALUMINUM WIRING HAZARDS & REPAIRS
AMPS & VOLTS DETERMINATION
AMPACITY - the LIMITING FACTOR
APPLIANCE EFFICIENCY RATINGS
BACKUP ELECTRICAL GENERATORS
BACK-WIRED ELECTRICAL DEVICES
BOOKSTORE - ELECTRICAL
BUILDING SAFETY HAZARDS GUIDE
Cadet & Encore Heater Recall
CIRCUIT BREAKER FAILURE
CIRCUIT BREAKER SIZE for A/C or HEAT PUMP
Classified CIRCUIT BREAKER WARNING
CORROSION in ELECTRICAL PANELS
CORROSION & MOISTURE SOURCES in PANELS
CUTLER HAMMER PANEL FIRE
DEFINITIONS of ELECTRICAL TERMS
DIRECTORY OF ELECTRICIANS
DMM Digital Multimeter HOW TO USE
ELECTRIC METERS & METER BASES
ELECTRIC MOTOR DIAGNOSTIC GUIDE
ELECTRIC MOTOR OVERLOAD RESET SWITCH
ELECTRIC PANEL AMPACITY
ELECTRIC PANEL INSPECTION
ELECTRIC PANEL MOISTURE
Electric Power Frequency Table
ELECTRICAL DISTRIBUTION PANELS
ELECTRICAL GROUND SYSTEM INSPECTION
ELECTRICAL SERVICE DROP
ELECTRICAL SERVICE ENTRY WIRING
EMF RF FIELD & FREQUENCY DEFINITIONS
FEDERAL PACIFIC FPE HAZARDS
FIRE SAFETY Checklist, CPSC
GFCI PROTECTION,Testing GFCIs AFCIs
HEATING COST FUEL & BTU Cost Table
HEAT TAPE USAGE GUIDE
Hertz - Definitions of KHz MHz GHz THz
KNOB & TUBE WIRING
LIGHTING, EXTERIOR GUIDE
LIGHTING, INTERIOR GUIDE
LIGHTNING PROTECTION SYSTEMS
LOW VOLTAGE BUILDING WIRING
LOW VOLTAGE TRANSFORMER TEST
MAIN DISCONNECT AMPACITY
MOISTURE SOURCES in PANELS
MURRAY SIEMENS Recall
PHOTOVOLTAIC POWER SYSTEMS
PUSHMATIC - BULLDOG PANELS
REMOTE ELECTRIC POWER, PHOTOVOLTAIC
RUST in ELECTRICAL PANELS
SAFETY for ELECTRICAL INSPECTORS
SE CABLE SIZES vs AMPS
SIEMENS MURRAY Recall
UNDERGROUND SERVICE LATERALS
VOLTS / AMPS MEASUREMENT EQUIP
VOLTAGE MEASUREMENT METHODS
WIND ENERGY SYSTEMS
WIND TURBINES & LIGHTNING
ZINSCO SYLVANIA ELECTRICAL PANELS
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). Details about how to wire up an electrical receptacle are at CONNECTION DETAILS - where to connect black, white, red, green, ground wires.
Watch out: mis-wired electrical receptacles are dangerous. This article series describes how to choose, locate, and wire an electrical receptacle in a home. 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. Also see SAFETY for ELECTRICAL INSPECTORS.
Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved.
The 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
Readers of this article should also see Electrical Code Basics, ELECTRICAL DEFINITIONS and also SAFETY for ELECTRICAL INSPECTORS. Our photo at page top is not an example of a proper electrical outlet installation.
Connect the Ground Wires to the Receptacle
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
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.
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.
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.
Green link shows where you are in this article series.
Frequently Asked Questions (FAQs)
Question: When wiring an electrical receptacle, what do I do with the red wire? Can I ground it?
I have a 3 wire (Black, White, Red and ground) feeding a outlet and I want to add another receptacle to run further down the line. The line out is 14/2. What do I do with the Hot Red wire? Can i attach it to the ground. - Rick
After capping off the red wire, can I extend the line to the next plug by following the diagram above and adding the black and white wires to the respective second screw connections?
You see, the wiring has already been installed by the builders and they left the boxes without receptacles so all I have to do is connect them to the. I don't know why the extra red wire is there. It was done over a year ago. I want to finish the connections. It runs 14/3 and then 14/2. That's why I have the extra red.
Reply: how three-wire circuits or multiwire branch circuits with a common neutral (and ground) are used and wired
Rick often electricians run a 3-wire system into a building area using two hot wires and a shared neutral, to permit providing two circuits in an area while having to pull just one wire to the area. But to sort out how your wires were connected and are being used requires some expertise, visual inspection, and testing using a VOM.
Take a look at multi-wire branch circuit wiring information and hook-up details at MULTI-WIRE CIRCUITS.
Question: how is an electrical outlet wired to the electrical panel?
how do wire the outlet plug to the electrical panel - Anon
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,
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
Questions & answers or comments about how to install and wire electrical outlets or receptacles in buildings.
Ask a Question or Enter Search Terms in the InspectApedia search box just below.
Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.