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Designing and Installing Outdoor Lighting

Description/Purpose:

Low voltage outdoor lighting can be used in a landscape to provide safety, security, accent, and character. The specific design of a lighting system will be influenced by a variety of things, including the site characteristics, the scope of the landscape, its function, and the homeowner's desires.

Types of Outdoor Lights:

  • Uplights: Lights placed at ground level with the lights aiming upward to highlight focal points in the landscape, such as specimen trees, signs, and architectural features. The lights not only highlight features from the outside, but they also provide for an extension of the interior living spaces at night. Fixtures of this type may include spot or flood lights as well as in-ground fixtures.

  • Downlights: Lights placed above an object or area and aimed downward to imitate natural light such as simulating moonlight, or for providing security to an area, such as at back entrance. Care should be taken to hide or shield these light fixtures from view to create a true natural light. Fixtures of this type include spot or flood lights.

  • Backlights: Lights placed behind artistic objects or plant material to cast a silhouette on a wall for a striking effect. As with downlights, care should be taken to place the fixtures so that they are hidden from view. Lights of this type may include spot or flood lights as well as in-ground fixtures.

  • Pathlights: Lights placed just above grade level along sidewalks, driveways, or informal paths in the landscape to safely lead a person from one location to another. Path light fixtures are generally low to the ground and cast a spreading light.

  • Specialty lights: Lights that add accent to a space, especially in the evening. Their purpose is to set a particular mood or create atmosphere. Examples of specialty lights include string lights in a gazebo, lights that resemble patio torches and/or flickering flames, and lights used in underwater settings to highlight a waterfall or rock bank.
Amount, Specifications & Supplies:
  • Lighting fixtures chosen based on the landscape, home, budget, and user's tastes
  • Electrical source (120-volt)
  • Correct size of wire based on number of fixtures and transformer size
  • A correctly sized transformer that has been chosen based on number of fixtures and for such features as indoor or photoelectric control
  • A length of conduit to run the wire under a sidewalk or driveway
  • 1 1/2" galvanized screws for mounting the transformer (deck or concrete screws depending on the location)
  • Small flags or stakes to mark the location of the light fixtures
  • Electrical staples to attach cable to building
Tools and Equipment:
    Design

  • Blueprint of landscape design
  • 100' measuring tape
  • Graph paper or drawing paper
  • Lighting fixtures catalog
  • A few flashlights with varying degrees of intensity to test locations for light fixture placement

    Installation

  • A garden hose for marking underground wire placement
  • A squared-nosed shovel for cutting a trench to place the wire into the ground (a lawn edger may also be used)
  • Wire cutter/stripper for cutting wire
  • Landscape rake to move mulch or rock for installing and covering the cable
  • Screwdriver and drill to mount the transformer
Site Considerations:

The amount and type of lighting will depend on the function and character of the landscape and the desires of the homeowner. A variety of lighting types may be used in outdoor landscapes including path/safety lighting, security lighting, silhouetting, grazing, up-lighting, down-lighting, and more. For illustrations on various lighting techniques go to How to Plan Your Landscape Lighting (http://www.weberelectricsupply.com/Ambiancep2.html) at Weber Electric Supply.

Before designing and installing an outdoor lighting system, a number of important issues should be addressed:

  1. Consider outdoor lighting only after all of the landscaping elements are installed. This will allow you to see all the aspects of your design and how outdoor lights will accent them. Make your lighting system flexible to change as plants grow.

  2. Before commencement of any digging, a utilities locator, such as Minnesota's Gopher State One (651-454-0002), should be called to locate all underground pipes and wires. If you have an irrigation system, it will also be important to know the locations of controller wire, pipes, and sprinkler heads.

  3. Check with your local municipality to determine if a permit is needed and to locate property line easements.

  4. If you have sidewalks and/or driveways cutting through proposed lighting areas, it will be necessary to run a cable underneath them. It is best to hire a professional to install conduit under these obstructions.

  5. A licensed electrician will be required to wire an outdoor receptacle and/or switch to control the new lighting system and may also be needed to establish a circuit and install the fixtures for outdoor flood lamps.
Step-by-Step Process:
    Design

  1. Refer to a copy of the landscape design blueprints or measure and sketch a scaled plan on graph paper. Include the house, other structures, driveway, walkways, steps, large trees, gardens, specimen plants, etc. as illustrated below. Information on developing a base plan can be found at http://www.sustland.umn.edu/design/module2.htm.

    Figure 1. A typical residential landscape plan

  2. Choose the desired focal points -- the entrance, a large tree, fountain, or other interesting feature within the landscape. Select no more than two focal areas and sketch them onto the plan.

    Figure 2. Locating focal points and trafficked areas

  3. Select the high traffic areas, such as driveways, walkways, decks, and steps that need to be illuminated. Determine the desired lighting and effects needed for these areas; use a flashlight, after sunset, to test the location and illumination effects. For example, walkways usually require low lighting, which spreads horizontally across the path.

  4. Choose the type of fixtures best suited to the landscape from an outdoor lighting catalog. There are a variety of fixtures to choose from, with an array of wattages and lighting radii. These fixtures include directional/spot lights, floodlights, pathway lights, deck and patio lights, underwater lights, and more.

  5. Determine the positioning and spacing for each type of fixture based on your lighting needs, and plot them to scale on the plan. The figure below contains walkway lights shown as single dots and down-lighting fixtures shown as circled dots.

    Figure 3. Plotting out the spacing and positioning of fixtures on the landscape plan

    For photographs of the different types of lighting fixtures go to Nightscaping® at http://www.nightscaping.com and click on the different lighting types located under "Products." For a detailed description of each fixture, click on the fixture photos.

  6. Locate your electric source and determine the total length of wire you need to supply all of the fixtures. Run wires so that they do not interfere with normal landscape maintenance (mowing, aerating), or obstructions such as utility pipes, meters, cables, shrubs and trees. Remember that with most systems, multiple fixtures can be run off of the same cable. Twelve-gauge double wire is standard, but 10-gauge and 8-gauge wire is also used when resistance is a problem due to long wire runs or too many fixtures. Most residential outdoor lighting uses a 120-volt outlet as an electric source, which is converted to a much safer 12-volt system through the use of a transformer.

  7. Select a position for the transformer and controller that is easily accessible, located near the power source, and close to where the fixtures will be installed. The wire should begin and end at the transformer creating a looped run. Avoid straight wire runs of more than 100 feet and looped runs of more than 200 feet.

  8. Calculate the required size of the transformer needed based on total wattage of the fixtures. More than one transformer may be necessary depending on the size of the system. From our example site above, we need 9 pathway and 2 down-lighting fixtures. Down-lighting is illustrated below.

    Figure 4. Downlighting

    The following calculations are used to determine the size of the transformer needed for our residential site example:

    9 path lights x 18 W     =      162 W
    2 down-lighting lights      x      50 W     =      100 W
    262 W

    A 300-watt transformer would be adequate to supply this lighting system; however a larger transformer may be desired to allow for further expansion. The additional wattage of the transformer should not exceed one-third of the total wattage needed. Transformers can range from 150-watt to 900-watt. For this example, the transformer could be placed near the electric source along with the controller for easy access. Controllers can range from simple switches to motion and light detection sensors to automatic timers. The type of controller will depend on the desires of the homeowner.

    Installation:

  1. Determine if the electrical cable will need to be run under sidewalks, driveways, patios, etc. Install conduit under these elements to protect the cable. It is best to hire a professional to install the conduit.

  2. Consult a licensed electrician to install an outdoor GFI outlet and/or wire an additional circuit and switch to power the lighting system.

  3. Flag or stake the locations of the light fixtures and adjust them if necessary to avoid damage from snow removal equipment, lawn mowers or aerators, tree or shrub branches, and gutter downspouts. For above ground fixtures, place a flag at the base of where the fixture will be located.

  4. Assemble and position each light fixture in its desired location, but do not put them in the ground or hang them from their desired location yet.

  5. Place the cable, based on the lighting plan, along each fixture run leaving an additional 12-24" of cable at each fixture depending on the size and manufacturer of the fixture as well as the location. This will allow for fixture attachment and for possible relocation in the future. Additional cable should be left at the transformer location(s) for system hook-up.

  6. Attach the cable to the fixture. The method by which this is done will vary depending on the manufacturer and type of light fixture. Most systems run the cable through the fixture's stake where it is connected to the light bulb and then down the stake to the next fixture. For specific installation instructions, consult the lighting installation guide that came with the fixtures. When installing the fixtures, be sure that the connections are secure and free of dirt or dust.

  7. Install the transformer in the desired location making sure it is placed out of the reach of children and animals. Use the screws and staples, if necessary, to hang the transformer and cable.

  8. Plug the transformer in and test the lighting system for operation. Check for loose connections and chafed or cut wires.

  9. If all the components are in working order, bury the cable underground or beneath the mulch. In planting beds, bury the cable in a trough created with a landscape rake and cover the cable with the mulch. It is not necessary to position the cable under landscape fabric, but be sure that the cable is 2-4" below the mulch. To bury the cable under turfgrass, use a square-nosed shovel to slice a 4-6" deep trench along the run. Insert the cable in the trench. Replace the turfgrass and "seat" it by stepping on it. A motorized lawn edger will also cut in a trench. If fixtures are above ground, the cables can be stapled to trees, posts, or walls using electrical staples.

  10. Finally, imbed the fixtures in the ground or hang them from their desired locations. This is also the time to make any adjustments to the direction of the light or the final position of the fixtures.


References:

Landphair, H. and F. Klatt. 1999. Landscape Architecture Construction. Prentice Hall PTR: NJ.

Night Lighting. 2000. "The Romantic Ambiance of the Nightscape," http://www.igin.com/Landscaping /ambiance.html.

Nightscaping®. 2000. Available at: http://www.nightscaping.com.

Outdoor Lighting Perspectives. 2000. http://www.outdoorlights.com.

Sauter, D. 2000. Landscape Construction. Delmare Thompson Learning.

Weber Electric Supply Website. 2000. "Cable/Fixture Layout Guides," http://www.weberelectricsupply.com/gde.html and "How to Plan Your Landscape Lighting," http://www.weberelectricsupply.com/Ambiancep2.html.


This implementation report was developed by Amy Berquist and Alex Stuedemann, students, University of Minnesota Department of Horticultural Sciences.

 
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