By convention, the white wire is neutral , the black wire is hot, and a green or bare wire is ground. The simple explanation is that every color used for electrical wiring has a specific meaning, with different colors indicating different circuit types and purposes. NEC imposes the following electrical wiring color standards: Ground wires : green, green with a yellow stripe, or bare copper. Neutral wires : white or gray. If the multi-colored wire is black and red, the black wire is the negative wire , while the red one is positive.
If both wires are black but one has a white stripe, the striped wire is negative, while the plain black wire is positive. How do you know which wire is hot and black? Place the prong of the multimeter's black wire on the bare metal on the end of a white wire, then read the meter.
If you get a reading, the black wire is hot; if you don't, the black wire isn't hot. Can red and black wires go together? In volt circuits, red wires are the secondary live wires. Like black wires, they can be used in some types of switch legs.
They are also used to connect hardwired smoke detectors to the home's power system. A white wire being used this way should be marked, but it might not be. So be careful with In a 4-wire volt setup, white should be common. The hot wires can be black and any other color besides white, gray, or green. On this multimeter, you use the setting in the lower right to measure AC voltage. You have to do this with the power on, so be very careful.
Once you figure out what the mystery wires are, writing a note on the back of the faceplate with a permanent marker is always a good idea. If you find an odd-colored wire, you can use a multimeter to figure out what it does. With the power back on, touch one lead from the multimeter to the white wire and the other lead to the mystery wire.
If you have more hot wires than you need for your application, cap the unused wire off with a blue wire nut to prevent short circuits. That may help you avoid confusion in the future.
One other thing to consider. Lighting circuits are often run with wire gauges that can carry less current as lights do not normally draw as much power as appliances plugged into duplex outlets. Using a higher number gauge, which is a thinner wire, saves money during construction but means it can only safely carry a lesser current. I am not a licensed electrician. The electricians are licensed to know the local electrical codes where they work.
Having practical knowledge does not mean wiring you do will be considered up to code or safe in the eyes of code enforcement. This can affect resale value of your home and more importantly, affect safety for your homes occupants.
You will need to turn off the power to the switch you are wiring to. You will need to verify which breaker powers that switch, unless you turn off the main breaker in which case an assistant with a flashlight is recommended.
Even with the main breaker off, it is wise to verify there is no measurable voltage present on the hot wire you are tapping off of before you start your work. It is also wise to ensure no helpful but misguided family member is present who might decide to turn the breaker back on while you are working. Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams?
Learn more. In a light switch, how can I tell if the black wire is really hot and the white wire is really neutral? Ask Question. Asked 1 year, 5 months ago. Active 1 year, 4 months ago. Viewed 28k times. Improve this question.
JACK Jason Thompson Jason Thompson 3 3 gold badges 5 5 silver badges 10 10 bronze badges. The way to do this safely is to call an electrician. It sure looks like this switch is wired to switch the neutral instead of the hot. That's a big bad no-no. Either that or all the wire colours are backwards One way or the other, this was installed by a drunk.
Be careful with youtube videos - they might show you part of how to do something right but they won't give you the experience to notice when something is very wrong. Does your location in the world even permit power sockets wired to lighting circuits? To back up what Criggie says - this would not be allowable in the UK - lighting circuits should not be used for power, or vice versa.
Show 10 more comments. Active Oldest Votes. Improve this answer. Thank you for your response. I'll admit that AC is still a mystery for me and I think I'm figuring out that my initial mental model is incorrect. My I think incorrect mental model is that the wires took turns as to which one supplied electricity. But if I'm hearing you right, the neutral only has a current if it is fed by the hot.
That is to say that the electrical panel doesn't push electrons through both wires, but pushes and pulls through one wire.
Is that correct? JasonThompson the panel doesn't push and pull, it just supplies power. The appliance "takes" what it needs from the circuit breaker wire and sends it back through the neutral or return wire. It is a loop system. If it's a V appliance like an oven, then the two breaker "take turns" supplying power. JasonThompson If the appliance "takes" more than the rating of the breaker, the breaker will trip. The difference is that neutral is tied to ground somewhere in the electrical system usually in the main panel.
Hook an appliance across those two hots and it sees the difference, V. Picture 2 D-cell batteries connected end to end like in a flashlight.
These wires only connect to other green wires and act as a failsafe, allowing for electricity to have a place to escape. They can carry significant current, so treat them cautiously. These are the most common colors used in electrical wiring. Other color combinations, such as striped wires, may be used for other applications. Remember, black and red wires are always hot, meaning they are source wires that carry power from the electric service panel to a destination, such as an outlet or a light.
White wires augmented with red or black tape or markings are used as hot; however, a black wire can never be used as a neutral or ground wire, or for any purpose other than to carry a live electrical load. Blue and yellow wires are sometimes used as hot wires and as travelers, green wires and bare copper wires are ground wires, and white and gray wires are neutral. However, all electrical wires, regardless of their function, may carry an electrical current at some point and should be treated with equal caution.
We hope this list helps you differentiate between the colored wires in your home. If you are unsure of what any of these wires mean and what they do, it is important that you seek a qualified professional to answer any questions you may have.
While DIY options are feasible, dealing with the electrical issues in your home can be an overwhelming task.
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