Reverse Polarity

If you’d like to watch my video on reverse polarity instead of reading about it, here it is…

What is reverse polarity?

Reverse polarity is when an electrical outlet is wired backwards. It’s when the white wire is connected where the black wire should be and vise versa.

To orient you a little further, an electrical system in a home typically has 3 wires going to a standard electrical outlet. Two of them are covered with insulation and one typically has no insulation. The insulation on the wires is a different color for each wire depending on what it does. Black for the ‘hot’ or ‘energized’ wire. White for the neutral wire and the bare wire has no insulation and is a ‘grounding’ wire used to make they system safer.

If you touch the metal inside a black wire and at the same time touch something connected to a neutral wire, grounding wire or ‘earth’ (dirt, concrete, a puddle, a ‘grounded’ device, etc.) you will likely get shocked. And you may be killed or injured by the shock. This is because the electricity ‘comes from’ the black wire and ‘moves to’ the white wire.

If you touch the metal inside a white wire and at the same time touch something connected to a ground wire, or ‘earth’, as above, you will likely not get shocked unless there is a problem in the system. Do not do this to experiment though on a ‘hot’ electrical system. Disconnect power to the wires you are working on before touching anything.

How do you test for reverse polarity?

Testing an outlet for reverse polarity is easy if you have the right tool. The best tool is an outlet or receptacle tester. Here’s a link to the one I use at Amazon.com. You can also get one at most hardware stores. All you have to do is plug the tester into an outlet and interpret the light pattern that you see according to the chart on the tester.

Another way is with a ‘voltage tester’. This is a device that senses voltage when you put it near a wire or outlet. Here’s a link to one at Amazon.com. If you’re looking at a three-hole outlet and the roundish hole is on the bottom then put the tip of the tester in the right or shorter slot and you should read a voltage. The tester usually beeps or blinks. If you read a voltage on the left or longer slot the outlet is wired wrong. It has reverse polarity.

Will something work when plugged into an outlet with reverse polarity?

Generally, yes. Devices will work if they are plugged into an electrical outlet when the polarity is reversed. So you don’t know if there is reverse polarity unless you test for it.

Why is reverse polarity a problem?

There are a couple problems that I can think of with reverse polarity. One is that device manufacturers always put the on/off switch of a device on what they expect to be the hot wire as it comes into the device. If the polarity is reversed in the outlet the device is plugged into then the neutral wire is switched, not the hot wire. Then, if someone opens the device while it is still plugged in, which they shouldn’t, and they touch a component inside, which again the shouldn’t, that component may be ‘hot’ and the person may get shocked. If the outlet was wired with correct polarity the electricity should be stopped at the switch and the components inside should not be hot.

Another situation is a light socket. In a typical light socket there are two metal connections. One at the bottom of the socket and then the rim or threaded part of the socket. The one at the bottom, which is the hardest to touch, is supposed to be the hot connection while the rim is supposed to be neutral. If the lamp is plugged into an outlet with reverse polarity and the switch to the light is off, the rim or threads will still be energized or hot, and if you touch them you will likely get shocked. If the outlet is wired correctly and the switch is off neither metal piece inside should be energized. Still, unplugging a lamp before changing a bulb is the safest thing to do.

How do you fix reverse polarity?

Fixing reverse polarity in an electrical outlet is pretty simple. Here are the basic steps:

  1. First you need to disconnect power to the outlet at the main electrical panel.
    1. Using an outlet or voltage tester, as describe above, is the best tool to determine if power is off to an outlet.
    2. Otherwise you can use a known- working lamp.
      1. Plug the working lamp into the outlet and make sure the lamp lights.
      2. Turn off breakers in your electrical panel until the lamp goes out.
      3. Double check with another known-working device like a toaster that the outlet is not energized.
  2. Remove the outlet cover – usually one screw
  3. remove the outlet – usually two screws
  4. Move the white wire to the side where the black wire is and vise versa.
  5. Put everything back together.
  6. Turn on power at the electrical panel.
  7. Test that the reverse polarity is corrected as directed above.

Note that I am not a licensed electrician and I’m really not qualified to teach anything. This document is for entertainment purposes only.

2 thoughts on “Reverse Polarity”

  1. Hi just saw your video on YouTube about reverse polarity. Thank you for the information. I’ve recently discovered 4 receptacles in my kitchen read reverse polarity and upon taking off covers noticed they’re wired properly. Any ideas where my issue can be? Any advice would be great! Thank you

    1. Those outlets you checked get their electricity from other outlets and eventually back to the main electrical panel. I would find the breaker in the electrical panel that turns off those outlets in your kitchen. Turn off that breaker, then figure out what other outlets or lights don’t work. Check the wiring at those locations. Be sure to look for outlets in unusual places like behind appliances and under sinks. Feel free to contact me via the contact page at HouseKnowHow.com if you need further assistance.

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