Outdoor lighting

Outdoor lighting systems are commonly referred to as low-voltage lighting. The lamp in your living room is using 120 volts. Most landscape lighting systems utilize 12 volts.

My mother-in-law’s Christmas gift is complete.

I detailed the process of redesigning her front yard over my last few columns. The last step was to install one of the most underutilized aspects of the landscape. Outdoor lighting is not just about illumination, it adds an entirely new dimension to the design.

For simple outdoor lighting systems, all you need are uplight fixtures and path lights. There is such a thing as light pollution, but low-voltage fixtures in the landscape produce a low amount of light and don’t contribute to sky glow. Downlights provide wonderful effects on trees as well as paths. However, they require much more effort to mount and service.

Our first step was to determine what we wanted to light. We wanted to avoid the common mistake of overlighting. The dark spaces between the lights are as important. We decided to uplight three crape myrtles. The bark will provide interesting shadows and colors. The sidewalk would only require three staggered pathlights.

Outdoor lighting systems are commonly referred to as low-voltage lighting. The lamp in your living room is using 120 volts. Most landscape lighting systems utilize 12 volts. By comparison, this is very safe and requires minimal experience to install.

A transformer will be required to change the 120 volts coming out of the outlet to 12 volts that will go out to the lights. Transformers are typically nondescript black boxes that have a timer or light sensor to turn lights on. A sensor is convenient as day length changes throughout the year.

Watts are a measure of power. On old-fashioned incandescent bulbs, 60-watt bulbs were typical for a living room lamp. For quite a while, landscape lights utilized halogen bulbs, an efficient incandescent bulb that did not color-shift as it aged. However, LED bulbs are much more energy efficient and more commonly used. A 10-watt LED bulb will put out the same amount of light of a 60-watt incandescent.

Transformers are sized by the number of watts they produce. We decided on a 45-watt transformer because our lighting system utilized three 5-watt uplights and three 3-watt path lights. That’s a total of 24 watts. A 45-watt transformer will have plenty of wattage and we can still add lights at a later time.

Wire is the conduit for electricity.

A multistrand bundle of copper wires is bound within a black insulator. For landscape lighting, two wires are attached as a single circuit. Electricity needs to flow in order to work, so it travels out to the lights on one wire and returns to the transformer on the other.

Wire size is referred to as AWG, or American Wire Gauge. The lower the number, the bigger the wire. It’s important to use the correct gauge. If the wire is too small, lights won’t operate properly. In outdoor lighting systems, 12-AWG to 18-AWG are typically used. The larger wire is more expensive because there’s more copper.

There’s a voltage loss formula to calculate which wire is suitable that involves the total number of watts and length of wire. However, this column isn’t long enough and you probably don’t want to know it, anyway. The good news is that LED bulbs have made it much easier to choose wire because they use few watts.

Long wire runs often require larger wire. Since we were only doing the front yard, we used 16-AWG wire. If we were running it all the way to the backyard, we might have upgraded to 14-AWG or 12-AWG.

Connecting lights to the wires can be as simple as using quick connectors that come with each fixture. They are easy to set up and work reasonably well. We chose to use grease-filled wire nuts to make our connections. They will provide long-term protection against corrosion and are less likely to be faulty.

With all the lights working, the real treat came that night. With very little ambient light from the surrounding area, our fixtures were adjusted for maximum impact.

The Christmas gift was complete.

Tony Bertauski is a horticulture instructor at Trident Technical College. To give feedback, e-mail him at tony.bertauski@tridenttech.edu.

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