Sometimes you open an outlet and it has more wires connected on the inside than you thought it would. In many cases you will find two black wires and two white wires, but sometimes you will find four or five or even more than six! So, why are there two black and two white wires in your outlet box?
There are two black and two white wires in an outlet box because the outlet is in the middle of a series circuit, accepting power from another source and sending it on. Two cables are hot wires, bringing the power in and carrying it onward to the next. Two cables are neutral and do the same.
If you are re-wiring the outlet yourself this can be confusing, but it is not unusual or wrong to have more than one set of black and white wires in your outlet box. Each wire serves a purpose and understanding each one will give you confidence when working inside an outlet.
If you are unsure at all about the wiring in your house it is best to get a professional in to wire the outlet as faulty wiring may cause fires and other damage. But knowledge is always a good thing and being able to understand and wire your outlets is handy. Or, you may simply want to know what the electrical professional is talking about when they mention the four wires in your outlet. After a few minutes of reading this post, you will have a good idea about why there are two black and two white wires in your outlet (and what to do about it!)
Identifying The Different Wires In An Outlet.
For electrical circuits to work there must be: one wire to receive electric current into the outlet (often referred to as the ‘hot’ or ‘live’ wire); and one wire to send it on (usually referred to as the ‘neutral’ wire), this completes a circuit and allows electric current to ‘flow’. When an outlet is connected in the middle of a circuit it will generally have more than two wires because two hot wires bring power in and carry it out to the next outlet while two neutral wires do the same. There may be another wire as a ground wire and there may also be another wire if the circuit is branching in two directions from this outlet. So there may be as many as six wires or more in a given outlet. This is completely normal in the wiring of an outlet.
This table may be helpful to understand this:
|Black||Live/Hot wire||Carries the electric current from the breaker panel into the switch or light source|
|White||Neutral wire||Carries any unused electric current back to the breaker panel.|
|Plain (no color covering) or green||Ground wire||Carries electric current back to the breaker panel, then to a rod that’s buried in the ground preventing the circuit from ‘grounding’ through a person or other conductive object.|
What It Means When There Are 4 Wires In Your Outlet
Having more than two wires in an outlet simply means multiple outlets are using the same electric circuit and this outlet is a middle-of-run electrical outlet.
If there are more than two wires in the outlet (one black and one white), it means it is part of a series circuit, that is, it has more than one light fixture or switches that needs to draw electric current from the breaker panel and they are connected in a daisy-chain fashion. A series circuit can have two or more outlets powered by the same wiring and circuit. The one set of black and white wires are the ones supplying electric current to the light fixture or switch and the other set is completing the circuit and goes to the next outlet down the line.
Is It Safe To Have 2 Black And 2 White Wires In An Outlet?
It is safe to have two black and two white wires in an outlet provided each wire is correctly attached to the terminal and insulated from contact with other wiring.
An outlet is designed to receive electric current from the breaker panel or previous outlet, use it to power something, usually a light or switch, and return any unused electricity to the breaker/service panel. Current enters along the black (hot) wire through other outlets, switches, and light fixtures on the circuit and begins its return to the source through the white (neutral) wire.
Provided each of these wires are connected to the correct place in the outlet box using the screw-in panels, insulators, and covers these will safely conduct the electric current. Most panels will have recessed screw-in holes, secure screws, or snap-over covers to ensure there are no exposed wires or places where contact can accidentally happen.
Important Safety Note
Whenever you’re working with any wiring or appliance in your home that deals with electricity, be sure to turn off the breaker switch on the service panel before opening any outlet or appliance.
Before removing any covers from an outlet switch off that circuit on the breaker panel and test to check that there is no current in the outlet using an outlet tester. Only once you are satisfied there is no electric current in the outlet should you proceed.
Also be aware that on a standard 120-volt receptacle, the three types of screw terminals will tell you what wires they accept:
- Brass-colored screws accept black wires (hot/live)
- Silver-colored screw terminals accept white wires (neutral)
- A green screw terminal accepts the bare copper (or green) grounding wire.
If the wiring system you are working with is old the wires may not be correctly color-coded, but if you remember that brass screws accept hot wires, and silver screws accept neutral wires you will be able to tell the correct terminals to attach the wires to. In some instances, a hot wire may be red.
Do I Need To Change Anything In A 4 Wire Outlet?
An outlet with two black wires and two white wires will only need to be changed if the outlets connected to it are no longer needed and are being removed from the circuit. Each of the four wires provide a specific function and cannot be changed unless the needs of outlet are different somehow. If you are removing a part of the series circuit, call in a professional to assist with rewiring. A circuit needs to be viewed as a whole system where one part impacts other parts connected to it and a professional will be able to assist with connecting all the parts into one whole.
There are often more than an expected two wires in an outlet box: two black wires, two white wires, green wires and maybe some others. This is completely normal and is usually because the outlet is in the middle of a series circuit, accepting power from another source and sending it on. Each wire has a purpose and if they are connected correctly in the outlet box and are insulated where necessary they will be completely safe. For safety it is still advisable to use an electrician or other professional to access and make changes to the wiring if you are at all uncertain about anything.