Best practices when working with electricity ?

[Ed, Fl]

Trying to save a few dollars, I thought I could replace a light switch by myself. I turned off the breaker for the room, and then I used the vacuum cleaner to make sure there was no power at the outlets.

When I tried to replace the switch, I got a shock when I touched the wires. How is this possible?

[home improvement guy]

Never touch the wiring unless the power to the home is shut off at the main breaker or the main fuse has been removed. Never take a chance when working with or around high voltage wiring. I can think of two scenarios that can cause such a shock when the power is turned off at a single breaker. The first is the room's light fixture is on a separate circuit with other lighting fixtures. You turned off the power to the outlets, but not the lights. It is important to test the switch you're working on to make sure there is no current to the wiring that could hurt you.


In articles published in the past, I received mail from electricians explaining they would provide a circuit to the room's lights and a different circuit to the room's outlets. Their reasoning was to provide lighting when the power was off to the outlets so they could work on the wiring to the outlets. The other situation is reversed polarity.


There are three insulated wires inside an insulated jacket of common residential wiring commonly referred to as Romex. The black wire sends the electrical current to the outlets or light fixtures and the white wire is neutral and returns the current to the electric panel. The third is a bare copper wire for grounding of the circuits. In a properly wired situation where there is no power "on" to anything in the room, the white wire could be accidentally touched without receiving a shock. Reversed polarity often occurs when unauthorized people cross-splice electrical wires at a junction box, and in some homes the junction box is at the ceiling light fixture. When black and white wires are crossed in a light fixture's junction box, the current to the switch is through the white wire and you will receive a shock by touching what you thought was a neutral wire. White wires should not be switched.


Reversed polarity can also occur at a lamp base, and you can receive a shock by touching the metal socket when removing or replacing a light bulb. If an outlet has RP, the appliance plugged into the outlet can be damaged or any metal part on the outside of the appliance can be charged with an electrical current. Purchase a three-pronged circuit tester at any home, hardware or electrical supply store and check every outlet in your home. If only one outlet is discovered to have RP, hire a licensed residential electrician to make the repairs and to inspect all fixtures and junction boxes for reversed polarity.