Plan - Design - Install
Low Voltage Landscape Lighting
Table of Contents
Low voltage systems require the use of a transformer to reduce standard 120-VOLT power from your home to 12-VOLTS.
The transformer provides low voltage power to the lights. 12 volts is typical. (more thoroughly covered in components)
- Landscape Lighting Wire
Also called Landscape Lighting Cable - Connects lights to output from transformer.
This is two conductor wire designed for connection to + and - terminals on transformer, and connect to lights. The two wires from light fixture have no polarity choice. Does'nt matter which wire is which.
- Lights (Fixture and Bulb)
Decide what you want to light and which technique to use.
Fixture and bulb styles are available for desired lighting use and result; And there are lot of choices.
Todays LED bulbs using 7 times less power than halogen, and provide equal or better light out put.
Choose a fixture and bulb that can achieve the result you want. With some experimenting you can improve the look of the lights.
Different fixtures cast light in different ways.
LED light bulbs come with narrow to wide beam angles, color range from warm to cool and day light, and watt rating affects brightness.
Type of light produced; soft/warm light (2800 to 3500), cool light (3500 to 4100), day light (above 4100)
Light colors can make a big difference. Low numbers for softer mood lighting. Higher number lights things up better, plant foliage appears more natural; At least to the eye.
Fixture/Bulb combinations, create different light output, with different affects.
Start a Sketch
Create a drawing accurate enough to allow detail for a complete materials and component list.
Determine Light Requirements
- Accent lighting (Create new features with light)
- Mood lighting
- Light dark areas
Beam angle of bulb makes a big difference. A 20 degree beam angle focuses light output with a narrow beam angle. The spot light will use a narrow beam angle. A flood light, or wall wash light will use a wider beam angle.
- Up light a tree will require 1 or more spot lights. Spot lights can be a well light fixture (in ground level) or staked fixture (a few to several inches above ground). These will usually have a narrow beam angle and be on the bright side.
- A column of light up the side of a building hitting the roof over hang will use the same fixture and bulb as tree up lighting. Usually the narrowest beam angle, brightness is relative.
- Path lights less or more bright, the fixture style plays a role here. Some are designed to let light spread out a good distance, other fixtures are more like markers of light.
- Flood lights; Brightness is relative, usually wide beam angle.
- Warm or cool light? More on that below.
Fixtures that come with halogens can be fitted with LED bulbs. For a professional job, you use an appropriate fixture and bulb of adequate brightness, with a beam angle that best fits the result you are looking for. All the different fixtures that come with halogen bulbs, can be upgraded with LED bulbs. The bottom line is; 7 - 7 watt LED bulbs = 49 watts. 7 - 50 watt halogens = 350 watts. A 7 watt LED can out perform a 50 watt halogen. And the LEDs put out better light.
With LED bulbs you have
- Less Power Requirement
- Smaller transformer
- Smaller wire size
- Less power used = Less power loss
- Improved performance
- Arguably a more reliable system
Example Lighting JobMaterials List
Path Lights – 7 total
Well Light – 4 total
Light fixtures with 7 watt LED MR16
11 fixtures; 11 x 7watts = 77 watts
Transformer - 200 watt suggested, room for expansion
Landscape Light Wire (cable) - 100 feet used
Voltage drop calculations with 12 volt and 77 watts
#14 Wire - 4.03 volts drop farthest from transformer. Most modern transformers come with center tap feature where 15 volts DC is available to use. Voltage drop will still occur over the length of wire where fixtures at the far end farthest away from the transformer see a 4 volt drop down to 11 volts.
#12 Wire - 2.54 volts drop farthest from transformer. Here voltage drop at the farthest location from the transformer is only 2.5 volts. Improved performance with lights closer to same brightness.
#10 Wire - 1.6 volts drop.
A good strategy is to use #10 or #12 off the transformer as far as you can go with it, and use #14 or #16 to groups of fixtures. Smaller wire at fixture is easier to connect. Most fixtures use #18 - #22 AWG wire size.
To determine the transformer size you will need, add up the wattages of all lamps you plan to use.
- The transformer requires a 120 volt AC receptacle.
- In areas where winter snow piles up, the transformer should be mounted high enough to stay out of the piles. Melting snow is concern.
- Photo cell needs clear view of night and day. Photo cell should not be facing lights that turn on enough where the photo cell thinks it is day light out again. You can get a revolving door effect.A lot of transformers come with a photo cell with about a 60 inch reach wire. This makes placement easier. Garages, sheds anywhere there is power. Choose a location as close as possible to the areas to be lighted. Just because an a transformer is rated for outdoor use, doesn't mean it has to go out side. Mounting inside a garage and drilling a hole for the landscape light wire is good option.
The best placement for the transformer is as close as possible to the fixture locations. Sometimes it makes sense to use more than one transformer - especially when fixtures are situated throughout a large property. If multiple transformers are used then create a separate plan for each one. Mark transformer locations on your sketch.
A low-voltage transformer is an electrical device that changes voltage by inversely adjusting the current. A transformer contains a positive terminal and a common terminal. Your supply cable is connected to one of each terminal thus making a circuit as soon as the first quick connector is attached. The transformer is critical to your low-voltage landscape lighting.
The low voltage transformer is selected by first determining the total wattage being used in your plan. Select a transformer that has a higher wattage capacity than the total wattage being used; this will give you potential to expand or alter your design. You may need multiple transformers to achieve your landscape look. No single circuit may have more than 300 Watts of power, but one transformer can handle multiple runs of cable. The transformer will be placed close to the power source, and some are even rated for indoor installation. Your transformer must be at least one foot off the ground to avoid potentially rising water. All transformers must dissipate heat to cool; you should leave a 3-inch clearance around the transformer housing for indoor transformers.
- Choose Transformer Size
Transformer size is based on power output. Power output is measured in watts.
Transformers are not the large heavy things they used to be. Low power consumption LED lights allow for smaller, lighter weight transformers. Todays electronics and packaging provide easy to use features for lighting control.
Calculate expected power consumption
Add together the wattage of your individual lights
Multiply that total by 1.5
The new total is a safe transformer size, in watts. Any upgrades aside. Add future lights! Plan Ahead? Yes. Keep in mind, much of the it is more convenient to add a second transformer. Wire runs to separate areas is planning that keeps a lighting job more simple and expandable.
You can plug most low-voltage transformers into a GFI outlet. Save on cable by finding an outlet closest to your lighting needs.
Set Fixture Locations
Before you install any fixtures in the property, mark their approximate positions in the landscape using small flags or pencils. Indicate the positions on your sketch and mark what fixture types will go at each location. As you walk the property, make rough measurements to indicate the distances between fixtures and the transformer, and between the fixtures themselves.
- Landscape Lights
LED lights use less energy, allowing you to run your system on a smaller, less costly transformer
LED's last longer than other bulb types, and generate little to no heat. As mentioned above; LED bulbs using 7 times less power than halogen, and provide equal or better light out put.
A little light can go a long way outdoors. Create layers by using a combination of path lights, up lights and flood lights.
Determine Wire Runs
We recommend simply running cables along the ground and tucking them behind plantings or covering them lightly with dirt or mulch. Most light fixtures include stakes so you can simply insert them in the ground.
Across lawns Take a flat bladed spade and create a 4 inch to 6 inch deep slit and push the wire down in.
Boring under borders and side walks is common. For a sidewalk, dig an 18 inch deep hole on each side of the walk. At the bottom of each hole start an underground trench towards the other side. It is easier than it sounds.
Now, the task is to plan how to provide power to the fixtures. There are many wiring methods available. You don't want to run a single wire from each fixture to the transformer - 20 fixtures, 20 wires all ending at the transformer - that would waste a lot of wire. Instead, we minimize the total amount of wire by using one of the following wiring methods
Low voltage landscape lights should be wired in parallel when using output from a standard 12 - 15 volt DC transformer.
Lights wired in parallel will share equal voltage and show the same brightness according to the bulb wattage rating.
Lights wired in series; wires from fixtures are smaller wire size and will cause excessive voltage drop, wired in series as shown, the smaller wire size is not meant to carry this much load. The lights wired this way will appear dimmer and some may not come on at all.
Layout TIPS for Optimal Installation and Results:
Lower loads per run means lower voltage drop. This is not much of a concern for LED systems since voltage drop for most systems is minimal. But if your system is large (more than 15 fixtures or about 100W) break up your layout into multiple cable runs of ~ 100-150 watts per run. If you have more than 150 watts in an area -- break it up into 2 runs. For LEDs, lower wattages mean you can group more fixtures onto single runs, but keep in mind that it still makes sense to use one home run wire for each zone; this is more energy efficient and makes for easier troubleshooting.
Break your layout into Distance Zones. For example, put fixtures 15-30 ft away from the transformer on one run; fixtures 25-40 ft on another run; fixtures 30-50 ft on another run; and so on. The goal is to have all the fixtures on a run be roughly the same distance from the transformer so they have similar amounts of voltage drop.
Always start your calculations with 12-gauge wire. The voltage at a fixture is the actual voltage supplied (12 Volts) minus the voltage drop. The voltage supplied may be increased by use of a multi-tap transformer. These multi-taps have alternate voltage sources to counteract a long cable run with too high of a voltage drop. Another way to counteract a high voltage drop is change to a thicker wire, such as 10-gauge. If you need more voltage drop than you are getting, you may change to a thinner wire, such as 14-gauge, but a thinner wire supports less wattage.
Here is a chart to determine the maximum wattage allowed for each buried wire.
Gauge - Max Wattage
#18 GA - 120 W
#16 GA - 156 W
#14 GA - 180 W
#12 GA - 240 W
#10 GA - 300 W
#8 GA - 480 W
lightscaper.com - How To Design / Install Low Voltage Landscape Lighting