Replacing Switches and Outlets: Wire Colors, Screws and Safety

A non-contact voltage tester shows green when a circuit is dead and red when electricity is still running through it, and a red reading can mean the wrong breaker was turned off or that the switch or outlet is on a different breaker than expected. That check is the core of the safety steps in a Home Depot workshop on replacing switches and outlets, led by Robin Rebel.

Safety first

The workshop begins by turning off the breaker, ideally one labeled properly, then testing the circuit with a non-contact voltage tester. Everyone in the home should know electrical work is under way so nobody switches the breaker back on, and a sign on the breaker box can help.

Tools

Most tools are likely already in a toolbox: flat head and Phillips screwdrivers, needle nose or lineman's pliers, wire strippers, wire nuts and the voltage tester. A manual screwdriver is preferred over a drill driver because the screws are small and spaces tight. Wire nuts must match the wire size on the package. Inside boxes, only electrical tape should be used, not duct or masking tape.

Wires and switches

Most home wiring is non-metallic cable. In a label such as 14-2, the first number is the gauge and the second is the number of wires; the smaller the gauge number, the thicker the wire. Black is hot, white is neutral, bare is ground, and a red wire in 14-3 is a second hot.

Switches use brass screws for hot wires and a green screw for ground. To swap a toggle for a Decora switch, turn off the breaker, remove the plate, test, unscrew the switch, and photograph the wiring if unsure. Move the wires over, curling loops clockwise, with the stamped top facing up for up-on, down-off. Dimmers work the same way; the black wires go to the hot wires, and wire nuts join stranded to solid wire. A flickering dimmer may be caused by a bulb not marked dimmable.

Swapping a single pole for a three-way switch needs different wiring and often a 14-3 cable, so the workshop suggests an electrician.

Outlets

Duplex outlets come in 15 and 20 amp versions, the 20 amp having a T-slot. A 15 amp outlet can go on a 20 amp circuit, but not the reverse. Brass screws are hot and silver screws neutral. A third hole does not prove an outlet is grounded.

On a GFCI, line wires come from the breaker box and load wires go on to other outlets; the back of the outlet is labeled. To identify the line pair, separate the wires, restore power briefly, and find the hot pair with the tester, ideally with two people.

When replacing an outlet with a USB model, each screw can take up to two wires only when the hook method is not used; the wires are straightened and stripped using the guide on the back.