Outdoor Wiring Guidelines

TANAKA Juuyoh/FlickrOutdoor wiring is fairly similar to indoor wiring, with a couple of key differences. Outdoors, you have to protect all wiring and electrical devices from water and even excessive dampness. You do some of this indoors -- in kitchens and bathrooms for example -- but outdoors it's more comprehensive. You also have to protect outdoor wiring (and yourself) from run-ins with shovels, lawnmowers and other potential causes of a bad short circuit. Whether you're powering up an outdoor living room, a shed or a landscape lighting system, here's a general guide to your basic installation considerations.

Line-voltage and low-voltage

Line-voltage describes standard 120-volt household circuitry, the same wiring that powers everything in your house apart from 240-volt appliances, such as an electric range or central AC. In an outdoor wiring application, you use line-voltage circuits to power receptacles (outlets) and standard light fixtures.

Low-voltage wiring is found on most conventional landscape lighting systems. While these systems plug into a standard (line-voltage) outdoor receptacle, they have a transformer that "steps down" the voltage to the wires supplying the lights. This means that installing low-voltage outdoor wiring is relatively easy and often is done by homeowners (the system manufacturer should provide detailed installation instructions).

Wiring close to the house

For an outdoor living and entertaining space on a patio or attached deck, you might need only a receptacle or two, as well as some lighting (standard or low-voltage or both). For this kind of outdoor wiring, you probably can tap into an existing indoor circuit. If no circuit is available, or if adding new devices might overload the circuit, you'll have to run a new circuit from the breaker box. Chances are this can be done through the house, making installation easier. 

Wiring away from the house

Supplying power to a remote outdoor living space or an outbuilding often calls for a new, dedicated circuit with an underground cable. This is simpler than it sounds, but it does require a permit and careful adherence to the local building code. Typically you'll need to hire a licensed electrician. Once the main supply cable is installed, it can provide power to outdoor receptacles and light fixtures. Most codes specify 20-amp service for outdoor circuits, which is plenty of power for several devices.  

The right devices

Safety is critical with any wiring but is especially so with outdoor wiring. All receptacles must be GFCI (Ground-Fault Circuit-Interrupter)-protected, with either a GFCI receptacle or a GFCI breaker. Receptacles also should have a cover: One type seals the outlet from rain when not in use; another type has a plastic cover that shields the outlet's face even with cords plugged in. Line-voltage light fixtures must be rated for "damp location" if they're protected by a patio roof or eave. They must be rated for "wet location" if they're exposed to the weather. All surface-mounted electrical boxes must be watertight.

Outdoor wireless lighting

If you'd rather not bother running wiring throughout your yard to cut down on the cost for an outdoor lighting system or outbuilding, you have a couple of easy options. Solar landscape lights are self-contained little power plants with their own solar panels, storage batteries and lights controlled by a photocell switch (turns the light on only when it's dark). Pretty amazing, especially considering they cost about $3 to $5 apiece. As for outbuildings and other areas that need overhead lighting, the easy wireless option is to install a battery-powered LED light fixture. Many of these have motion-activated switches and photocells so they turn on automatically and only when they're needed.

Philip Schmidt writes for Networx.com.

Updated July 31, 2018.

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