Precautions necessary when wiring outdoor fixtures
Q. I am in the process of updating the landscaping around my deck with more lighting and a fountain. I have done indoor wiring before. What are some of the precautions when running wiring outdoors?
A. The basic wiring concepts for outdoors are similar to indoors except you must follow some additional safety precautions. It is very important to follow the electrical codes for your area for both your safety and the next owner of your home. If you do not and the next owner is harmed because you did not follow code, you may be legally responsible.
Outdoor wiring is susceptible to damage and degradation from water, animals and digging which do not present problems for indoor wiring. This is particularly true around landscaping where there is constant watering and digging in the springtime.
You will have to install a GFCI (ground fault circuit interrupter) for the outdoor wiring. This protects you from minor shocks caused by a partial short circuit or ground. The shocks are mild, but if they hit the nerves in the chest, they can stop a person's heart. These are often built into an electrical outlet on that wiring branch circuit.
People usually run the wiring outdoors from the attic or a basement/crawl space foundation wall. Coming through the foundation wall is usually the shortest route to the outdoor lights and all the wiring can be hidden underground. The major problem is drilling through the poured concrete or block foundation wall. If you attempt this, use a hammer drill with a masonry bit.
If you can make a fairly straight path from the house to the lighting and fountain areas, it is best to use TW wire in conduit underground. TW wiring has plastic insulation sheathing, but it is not stiff or particularly strong. This is why it must be enclosed in conduit for safety. Metal or plastic conduit is acceptable, but metal will better resist the impact from an accidental shovel impact.
Plastic conduit is easier to work with than steel or aluminum. Standard PVC conduit is often run aboveground when the wiring comes down from an attic. For the underground portion, HDPE conduit is used. Select 3/4-inch conduit because it is easy to work with. If the aboveground PVC conduit will be exposed to direct sunlight, paint it with latex paint to protect it from the ultraviolet rays.
The other wiring option is UF cable. This type of wiring has a thick, very tough plastic sheathing to protect the wires inside. With the tough outer plastic cover, it does not have to be run inside of conduit. It is good to use where the wire path has to have many bends which would be difficult to accomplish with conduit. It is stiff though and somewhat difficult to work with.
Once you have selected to type of wiring to use, select the outdoor receptacle boxes. Cast metal boxes with gasketed metal cover plates hold up the best over time. They seal very well and make a strong attachment point for the conduit. Keep the outlets at least a foot off the ground or higher if you experience heavy snowfalls.
Tools and materials required: hammer drill, masonry bits, lineman pliers, wire strippers, tiling spade, outdoor receptacles/switches, GFCI, wiring, conduit, wire nuts, electrical tape.
•Ms. Builder's column appears in Homes Plus. Send questions to Ms. Builder, c/o Daily Herald, 6906 Royalgreen Drive, Cincinnati, OH 45244 or visit dulley.com/msbuilder.
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