Back in the early 80’s we installed post lights along our driveway. We lived on a flag lot then and the driveway was about 200 feet long. The lights were spaced approximately 10 feet apart and buried in concrete. We made the mistake of not burying the wire deep enough (which came back to bite us in the back side later when we rototilled). Additionally, we didn’t use sturdy enough poles for our lights. Needless to say the job had to be redone a little more than 10 years later. Since then we’ve learned a few things.
If you plan on installing a light post there are a couple of really important considerations that you will need to make for sure.
- If you will be running new electrical wire it is important to be absolutely sure that the wire is buried at least 18 inches. There are alternatives, but this is the safest and least expensive method.
- Even at a depth of 18 inches we strongly recommend that you run you wire inside a very large plastic conduit that is many times the diameter of the wiring to be run. The tubing (and the wiring) should be waterproof and buried above and below layers of sand. Obviously, this would require the trench itself to be deeper than 18 inches.
- Even if the circuit already exists be sure that it is on a GFCI breaker. If not add one.
- If you are placing your post light on a pole that will be buried in concrete (as opposed to something bolted into a wall or curb) then you will want to consider a post made from thick, heavy-gauge tubing or install the post into a slip-fitting (a sleeve in the concrete).
Running an electrical circuit outdoors differs quite a bit from indoor wiring. Outside, water and extreme dampness are involved. Also, exterior wiring run underground is somewhat more accessible than the wiring in wall and ceiling cavities. A rototiller, an aerator and a pick or a shovel can easily slice through or chew up an electric wire. In a split second you can end up with a repair job that can take hours to complete and cost hundreds of dollars. Special wiring is available for direct burial that has an extremely durable casing meant to resist damage by dampness, water and abuse. However, the casing is plastic and can be cut. The standard alternative is to run groups of individual wire in a plastic conduit. Better yet we like running direct burial wiring inside a conduit instead – it’s the best of both worlds – sturdy waterproof wire in a damage resistant casing. Heat dissipation can be a minor problem here. Check with your local building department to find out what size conduit will work best for your project. Never use metal conduit below grade. It will rot in a matter of years. And always make sure to use wire that is 12 gauge or larger. Also keep in mind that 12 gauge wiring requires a 20 amp breaker.
Whether you decide to use conduit or the direct burial method it is wise to backfill your trench with a little sand first. Then lay the wire, and then a couple more inches of sand and finally native soil. Sand is less likely to damage the wire (or the conduit) and when you are digging in that vicinity late the sand warns you that wiring or conduit is near. If you can’t bury your wire at least 18 inches below grade then cover it with a little concrete (3-4 inches is plenty about 8-12 inches wide. Protecting a buried wire with a 4 x 12 inch concrete cover makes good sense. But be careful. Running a rototiller across a 4 x 12 inch concrete strip can ruin your day.
NOTE: All electrical connections should be made above ground in a special water-tight junction box. In other words, if your intention is to place the light 30 feet from the house then plan on purchasing one 50 foot long piece of wire for the task. Any connections you make between the house and each light will add unnecessary expense to the project. Never bury a high voltage wire junction. It makes no difference whether the connection has been contained in a waterproof box or not. Waterproof boxes rust and can leak. Nothing will blow a fuse quicker than water. And there is more water underground than you can shake a stick at. OK, if you must make a junction in the line then make it above ground. Be sure to use a watertight box to make the connection.
We goofed when we purchased our pole lights in kits and got second rate poles. They lasted about 10 years – literally a blip in time. Were we to do it again we would either use much heavier poles, or we would place less expensive poles in sleeved concrete piers. In other words we would either concrete in the best to if less than the best was all that was available we would be sure that our assembly was such that the pole could be replaced without removing the concrete support pier. In this way a less expensive pole could be replaced in a matter of an hour or so without any major complications.
When adding new exterior lighting it is wise (and a code requirement) to use a GFCI circuit. A GFCI breaker can be added to your electrical panel, but it may be easier (and far less expensive) to use a GFCI receptacle instead. No, you don’t have to plug your exterior connection into the receptacle. You can wire directly into the back of it using it. It becomes its own “mini breaker panel”.
Finally, make sure that all electrical boxes and connections are waterproof. Do this under the auspices of your local building department. The alternative could prove to be shocking. And, that’s all there is to it.
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