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Design a System

Design a System

The following design plan should give you an idea of what is involved in putting together a low voltage landscape lighting design.

Let's say we are planning to use 8 spot lights with 20 watts each, and 5 path lights with 10 watts each. This set up gives us a total of 210 watts.

Knowing how many total watts will be in our set-up will help us when choosing a transformer. There are several options to consider, but we will use the easiest one, a straight 300 wt. transformer with 2 sets of terminals. The allotted amount of voltage drop is estimated at 20%. What this means is that we must take the transformer wattage and deduct 20%, so we should only use no more than 240 total watts. Voltage drop occurs when electricity is lost due to distance or inadequate wire size.

Without using an ohmmeter, the general rule of thumb is as follows:

  • 12g wire will handle 100' and 100 watts
  • 10 gauge wire will handle 125' and 125 watts.
  • 8 gauge wire will handle 150 feet and 150 watts

For demonstration purposes, let's assume that all of our lights are going to run in a straight line with the furthest one being 100 feet away from the power source. We will use 12 gauge wire with 3 wire runs. We will put 80 watts on the shortest run, 70 watts on the middle run and 60 watts on the longest run. If the longest run was to be 125 feet away, we would use 10 gauge wire.

When we connect the fixtures to the wire we will use grease filled wire caps. It does not matter which ends couple together, as long as, the caps are tight.

Send us a photograph or digital picture of your house or yard and we can recommend a system design and fixtures that will work well in your situation. We can also digitally enhance the picture for you to see what your yard can look like with a dream lightscape. Please include some reference point and measurements.

Send photographs to: The Sprinkler Doctor 23705 Van Owen Street #213 West Hills, CA 91307

Attach digital images to email and send to the_doctor at lowvoltagelandscapelights.com or phone our west coast office at (818) 992-6353

Additional Tips

Low voltage (12 volt) systems are popular for landscape lighting for many good reasons. Low voltage systems are perfect for being creative when highlighting trees, gardens, artwork and other landscape features. Low voltage fixtures are easy to install because low voltage cable can be buried in a shallow trench, run through conduit or buried underground. A low voltage system is flexible because you can easily move fixtures around to accommodate the unique features of your yard or to change lighting effects. Low voltage systems are safe and energy efficient. Transformers reduce standard voltage from 120 volts to a safe 12 volts - so there is no risk of electrical shock to children or animals if the cable is accidentally cut.

Deciding What to Light

The first step in designing any lighting system is to determine what you want the light to do for you. Walk around your property, look out your windows and doors, and think about the kind of mood you would like to create. Do you want to emphasize a particular spot in your yard? Do you to create a safe pathway with lighting? What about creating romantic shadows with subtle moonlighting? How about making entertainment areas come alive with bright party lighting?

Next; try out different techniques, and have fun discovering the beauty of your yard at night. NOTE: Be sure the locations of your fixtures will not interfere with lawnmowers, traffic or be a source of irritating glare inside your house or to your neighbors.

Choose a Fixture

Once you have developed your lighting plan, select the style of fixture and lamps that best fit your needs. Remember, sometimes less is more...you do not need high levels of illumination coming from individual fixtures. Instead, use several fixtures at lower wattages for better effect.

Select a Transformer

Low voltage systems require the use of a transformer to reduce standard 120 volt power from your home to 12 volts. To determine the transformer size you will need, add up the wattages of all lamps you plan to use. Select a transformer that matches as closely as possible to the total lamp wattage. For example: if you have 11 fixtures all rated at 24.4 watts-you will need a 300 watt (VA) transformer. (11 x 24.4 = 268.4 watts). Generally, the total lamp load should not be less that one-third the transformer's wattage rating, nor exceed its maximum watttage capacity. If your total wattage is too high, either divide the load between two transformers or use a more powerful transformer.

Minimize Voltage Drop

The closer your low voltage fixtures are placed to the transformer, the higher their voltage (and wattage) readings will be. Those farther away you place the fixture the the lower the voltage it will receive. If a cable run is too long, or if too many lights are being powered by a single transformer, noticable voltage drop may occur. Voltage drop causes the lights farthest from the transformer to become dimmer then the other lights.

Voltage drop can be minimized in several different ways:

  • use heavier gauge cable
  • use a higher rated transformer
  • multiple taps
  • multiple transformers
  • shorten cable lengths
  • reduce individual fixture wattages
  • reduce the total number of fixtures on a run

Voltage drop can actually work to your advantage if differences in lamp brightness levels add a desired quality to your design. Lamps with lower voltage will last longer requiring less frequent replacement.

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