We wanted a simple light to illuminate the backyard and to serve as a focal point that divides the empty yard space between two houses. For this project, we chose a black-enameled aluminum three-head post light, Model 42278, made by Globe Electrical Co. Inc. The light costs about $150 at a local home center. Conduit, fittings, switch, cable, hardware, and concrete cost another $70. As with any electrical fixture installation, check with your local building department to see if any permits are required.
This project was originally published in the April 2001 issue of Popular Mechanics. You can find more great projects at Popular Mechanics DIY Central.
Step 1: Getting Power and Going Underground
The PVC coiduit that we used is RNC (Rigit Nonmetallic Conduit). This type of conduit can be buried. It's not to be confused with ENT (Electrical Nonmetallic Tubing), which is not rated for burial.
The conduit above the deck is EMT (Electrical Metallic Tubing), with rain tight fittings.
The first step is to use a posthole differ to rough out a hole that is about 18 in. deep. The, crosscut a concrete form so it is about 2 in. longer than the hole's depth.
Next, drill a hole near the bottom of the form, and fit the form with 1/2-in. dia. PVC couduit and a 90 degree elbow. Glue the pieces togeether with PVC cement. Center the conduit riser in the form, and tape the embow to the form. Protect both ends of the conduit by convering them with tape.
Set the form in the hole, and use a 2-ft.-long level across its top to ensure the form is level. Shovel concrete into the form and be sure to keep the conduit riser centered. Smooth the concrete with a hand float, and press the hold-down bracket into the concrete.
Step 2: Running Conduit
In case you are installing the conduit as we did, under a deck, you'll need to install a slip coupling and an LB conduit body when you get to the deck. The LB conduit body is the PVC fitting that - with the slip coupling - joins the vertical conduit to the horizontal conduit that comes through the deck. The slip coupling allows the conduit to move in response to settling soil.
Begin by gluing the slip coupling to the lower end of the 1/2-in. LB conduit body. Then, drill a 1-in.-dia. hole through the band joist of the deck. Glue a length of the 1/2-in. conduit to the LB fitting. Next, drive a screw through the LB conduit body's mounting tab and into the deck framing. Run the conduit under the deck, supported every 4 ft. with hangers. If you lack adequate headroom under the deck, you will have to remove deck boards to install conduit.
Step 3: Electrical Work
We installed separate insulated 14-ga. wires, avoiding cable, which is too difficult to pull through 1/2-in. conduit. We used a white, a black, and a green found wire. Pull these wires from the receptacle and switch box to the light. Leave at least 8 ft of excess wire above the concrete base.
Install the light heads on the post, and feed wires into the post from the bottom, until they protrude through the top. Then, connect the wire leads from the light heads to the circuit wires. Join like-colored wirese with twist connectors. For strain relief, takpe the wires together with vinyl tape. This keeps the weight of the dangling circuit wires from straining the connections. Stand the post up, and tighten it's bolts.
Now all that's left is the electrical connections at the house. The black wire from the light runs to the switch box. A second black wire runs from the switch box and is connected wbuy a pigtail to the black wire that comes from the house, and to the receptacle's brass crew.
Bring the white and green circuit wires from the light directly into the receptacle box, pigtail them to the white and green wires from the cable that comes from the house, and attach them to the outlet receptacle. The white wire attaches to the receptacle's silver screw, and the green wire to the green screw. The pigtailed black wire is connected to the brass screw.
Note: to ensure that the electrical assembly is safely founded, the switch must have it's own ground wire, and the metal conduit and fittings must be founded. A green wire from the switch box is connected by a pigtail to the cable that comes from the house and the green wire from the light. At the switch, it is pigtailed with two wires. One length from the pigtail attaches to the switch's green ground screw, the second is bonded to the switch box. Finally, connect the two black wires to the switch as shown. Mount the switch in the box and install a weather-proof switch cover.