DIY Wiring Diagrams for Electrical Receptacles
Also see:This page contains wiring diagrams for most household receptacle including grounded and ungrounded duplex outlets, ground fault circuit interrupters (GFCI) as well as 20, 30 and 50 amp receptacles for 120 and 240 volt circuits.
Grounded Duplex Receptacle
This is the standard wall outlet wiring diagram. This is a polarized device. The long slot on the left is the neutral contact and the short slot is the hot contact. A grounded contact at the bottom, center is crescent shaped. Don't use this receptacle when no ground wire is available.
This device can be controlled with a switch or wired to other outlets. Use a 15 amp device and 14/2 cable for a 15 amp circuit and a 20 amp receptacle with 12/2 cable for the 20 amp circuit below.
Ungrounded, Polarized Duplex Receptacle
This is an older version of the device above. The plug slots are different sizes but it lacks a grounding contact. This device does not make use of a ground wire. There is no protection against electrocution as provide by the grounded device.
When replacing a ungrounded, polarized receptacle use this type and not the grounded type above unless it is grounded to a metal outlet box that is tied to the house ground.
Ungrounded Duplex Receptacle
This is the oldest version of a wall outlet that you will find. It lacks a grounding contact and the plug slots are the same size. These devices did not make use of a ground wire and both hot and neutral were treated the same.
With this configuration any wire may be hot at all times and there's no protection against electrocution. When replacing an ungrounded device in an older circuit use the polarized one above and not the grounded receptacle at the top unless it is grounded to a metal outlet box.
Wiring a Ground Fault Circuit Interrupter
There are two sets of terminals on a ground fault circuit interrupter (gfci) receptacle: the line terminals and the load terminals. The source from the circuit should be connected to the line terminals and any standard duplex outlet or other device connected to the load terminals will be protected by this gfci. To protect a garbage disposal against a ground fault a switch/gfci combo can also be used as in this diagram.
To wire more than one GFCI receptacle in the same circuit, connect the source to the line terminals on each device using a pigtail splice. The load terminals are not used for this circuit. See more GFCI wiring diagrams at this link.
20-Amp 120-Volt Duplex Receptacle
A 20 amp, 120v duplex receptacle like this should only be install in a circuit using 12 awg or larger cable and a 20 amp circuit breaker.
When using this device for heavy appliances like refrigerators, washing machines and microwaves it should be connected to a dedicated 20-amp/120-volt circuit breaker.
20-Amp 240-Volt Appliance Receptacle
This outlet is commonly used for a heavy load such as a large air conditioner. The outlet should be wired to a dedicated 20-amp/240-volt circuit breaker in the service panel using 12|2 awg cable.
With this wiring both the black and white wires are used to carry 120 volts each and the white wire is wrapped with electrical tape to label it hot. This circuit doesn't make use of a neutral wire and the ground wire is connected to the ground terminal on the device. The slots are configured to accept only plugs from compatable appliances.
30-Amp 240-Volt Receptacle
A 30 amp circuit was once the norm for large, high voltage appliances like a kitchen range or clothes dryer. This type of receptacle provides 240 volts and 30 amps of current. The smallest cable allowed for used with a 30-amp circuit is 10 gauge, but 8 gauge may also be found. A 3-conductor cable is needed to carry a total of 240 volts and a neutral return. The circuit is wired to a dedicated 30 amp circuit breaker.
This arrangement makes it possible to power the heating elements in the appliance using the two 120 volts combined and one 120 volt wire to power timers and lights. This circuit is no longer used for new installations of high voltage appliances, for that a 50 amp circuit (pictured below) is now required.
50-Amp 240-Volt Receptacle
This wiring diagram is used for 50 and 60 amp circuits. The receptacle should be wired to a dedicated 50 or 60 amp circuit breaker using 6 awg cable. The 50 amp circuit is required for new installations of some large appliances requiring 240 volts. Two wires carrying 120 volts each can be combined to provide high voltage to heating circuits and one of the 120 volt wires can serve lights or other low voltage circuits in the appliance. The neutral wire provides a return path for the circuit and the ground wire provides extra protection from electrocution not found on older 30 amp, 240 volt appliance hookups.