Low Voltage Direct Burial Cable

Layout TIPS for perfect installation and results:

TIP #1

Lower loads per run means lower voltage drop. Break your layout up into multiple cable runs of around 100-150 watts per run. If you have more than 150 watts in an area -- break it up into 2 runs.

TIP #2

Break your layout into "Distance Zones". For example put fixtures 15-30 feet away from the transformer on one run, fixtures 25-40 feet on another run, fixtures 30-50 feet on another run, and so on. The goal is have all the fixtures on a run be roughly the same distance from the transformer so they have similar amounts of voltage drop. That way when you adjust for voltage drop by increasing the voltage for that one run, the lights are not over-volted or under-volted. For example, never have a fixture 20 feet from the transformer on the same run as a fixture 80 feet from the transformer. Why? Because if you use the 12v tap, the close fixture will have the correct voltage (about 11 volts) but the far fixture will only have about 8 volts and will be dim (because of voltage drop). However if you use a higher voltage tap to make the far fixture brighter, the close fixture will be over-volted (dangerous, fire risk, lights will be uneven, lamp lifespan drastically shortened). Anything over 12 volts dramatically reduces lamp life--13 volts cuts the lamp life in half!).

TIP #3

Don't "Daisy Chain" the fixtures. In other words don't connect fixture after fixture in-line to the same cable. You can do a couple fixtures in series, but we don't recommend exceeding more than 3 fixtures or 75 watts in series. Instead form T's or spider splices so that there is never more than 2 fixtures between any one fixture and the transformer. Example you might have 6 fixtures on a run but the cable layout is like a T with 3 fixtures on the upper left part of the T and 3 fixtures on the upper right part of the T. Even the end fixture only has 2 fixtures between it and the transformer. Why? Well as an analogy, if you had a hose and it had 6 equal sized holes, the first hole would squirt a lot of water but the last hole would only be dribbling water due to lack of pressure (i.e. voltage drop in electricity). However if you "T" off the hose, that is connect the water supply to the middle of that hose (between holes 3 and 4) the holes would squirt a more equal amount from each hole. You want to do the same with your low voltage cable layout—equalize the voltage to each fixture. Make sense?

TIP #4

For each run, bring the wire from the transformer to the middle of that zone, and then branch off more cable from there to reach different areas. This can be done with a hub or by simply splicing in more cable to form a "T" layout. This T layout somewhat incorporates objectives we discussed above in TIPS 2 & 3 –getting all fixtures with roughly the same length of cable to reach the transformer (TIP #2) and avoiding daisy chaining (TIP #3).

Layout Example:

For example if you have 4 path lights along a driveway each 10 feet apart, run the cable from the transformer to the area between fixtures 2 & 3 (even if it means passing fixtures 1 & 2 without connecting them). Then splice in a "T" with cable going back to fixtures 1 and 2 and cable going out to fixtures 3 and 4 – then connect the fixtures. This way electricity has to travel the same distance to reach the closest fixture (fixture #1) as it does to reach the farthest fixture (fixture #4). Additionally you only have 2 fixtures daisy chained in a row. If the farthest fixture is dim you can use a higher voltage tap on the transformer without over volting the closest fixture. All your lights in that distance zone/on that run have the same amount of cable to reach the transformer and accordingly will all have the same voltage and all be bright and even. It may seem odd to pass by a fixture with cable and then run more cable back to it—but what you are really doing is adding more cable distance to your close fixtures so that they equal the cable used in far fixtures.