How to Use a Non Contact Voltage Tester

Non-contact voltage testers provide the safest way to make sure the power has been turned off without touching any cables.

When you open an electrical box, you should:

  -cut the power to the outlet at the main electrical panel

  – make sure you turned off the correct circuit

Non-contact voltage testers can be useful for this purpose.  Testers will light up and make noise when they come close to a live (hot) wire, even those covered in insulation. During testing, the device cannot pass through metal sheathing or conduits.

The easiest way to test the tester’s batteries is to shove the tip into a live electrical socket or hold it against the cord or bulb of a lamp.  If the tester has detected voltage, you’ll hear continuous chirps or see a series of flashes. 

The tip of the tester should be put into the smaller (hot) plug slot when testing a receptacle. As a safety precaution, it’s a good idea to check the larger slot (neutral) in case the receptacle is wired incorrectly. If the receptacle is connected to a wall switch, make sure it’s on during testing.

Ensure that you have checked all slots in the receptacle in case they were wired differently or on different circuits. Pull the receptacle out and test each wire directly to confirm they aren’t live after you unscrew it. Additionally, it’s a good idea to test any other wires accessible at the back of the receptacle.

To test a power switch, unscrew and remove the cover plate, then place the tester nose against the screw terminals on the side of the switch.  It is safe to unscrew the switch once you have verified that the wires are not live and then test the other wires in the box.

If you are testing a light fixture, be sure the light switch is turned on and the circuit is turned off at the main panel. Once the light bulb is unscrewed, place the nose of the tester on the center socket button.

If there are two switches (on a three-way switch), test with one switch up as well as down. When you’ve confirmed that the fixture isn’t live, you can take it out of the electrical box and test its wires.

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