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Understanding Switch Leg Wiring

Master electrician Heath Eastman explains a common issue he finds in many folks’ homes—switch leg wiring—and explains how to fix it.

Kevin O’Connor meets master electrician Heath Eastman for a lesson on switch leg wiring. Heath explains that many homeowners have a switch in their home that doesn’t appear to control anything.

Heath tells us that, in many cases, these phantom switches are intended to control an outlet, but that renovation and repairs along the way could be the cause of the missing functionality.

Switches to Nowhere

Many folks have a switch on the wall somewhere in their house that appears to go nowhere. It doesn’t seem to activate a light, and nothing seems to turn on or off with a flip. Often, this switch is wired to an outlet, and the homeowner doesn’t realize it.

Switches can control entire outlets (top and bottom) or individual receptacles (top or bottom). When wired incorrectly, both outlets might have constant power at all times—even with the switch installed.

Switch and Outlet Wiring Can Be Tricky

When wiring a switch to just one outlet, there are some minor details to pay attention to. To wire the switch correctly, the power typically enters the receptacle first. The neutral wire will attach directly to the outlet, while the hot wire will be split. With a wire nut, the hot wire will splice back to one receptacle, but another wire tied into the same wire nut runs to a switch. A wire then runs back from the switch to the other receptacle. But, this will still result in constant power unless you…

Break the tab

There’s a small tab in between the two gold screws on most outlets. This tab is designed to be broken, and once it is, the two outlets can work independently from one another. One outlet can have constant power, while the other outlet operates on a switch. Sometimes, someone will replace a device and not know to break the tab, or they might’ve forgotten. If that’s the case, the switch on the line will appear to do nothing, while the problem is really within the actual outlet box.

How To Fix It

The hardest part about fixing this condition is locating the switched outlet. If you’re able to locate it (which will likely require removing the cover plates and investigating each outlet, you can easily fix the issue. All it takes is a pair of needle-nose pliers or a pair of diagonal cutters to break or cut the tab. Just be sure to shut the breaker powering the outlet first.