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Landscape Lighting Junction Box (a.k.a. J-Box, Hub, Ganged Splice, Junction Box, etc).

landscape lighting hubVOLT's Zone Control is a junction box where you make multiple connections for the fixtures in that area or zone. It is simply a compartment where one home run from the transformer enters the junction box and you branch several runs out to each fixture in that area.

There is nothing magical about a junction box or hub as some call them -- it is simply a compartment for containing all your splices for that zone. Junction boxes have the following features and advantages.

  • Equalizes voltage at fixtures. Typically, a home run wire is run directly from the transformer to the junction box; from the junction, each fixture lead wire connects to the junction. A long as the fixture lead wires are of equal length then every fixture will get the same voltage. This is very important for halogen lamps because they have a narrow range of acceptable voltage (10V to 12V); less important for LEDs since the range is much wider (8V to 15V).
  • Reduces number of splices. With daisy chain wiring, one wire is run from fixture to fixture - with a splice at each fixture: 36 fixtures = 36 splices. When junction boxes are used, up to 6 fixtures can be connected at each junction: 36 fixtures = 6 splices. Reducing splices saves time and money, and increases the reliability of the system over time.
  • Makes splices accessible. When splices are made in junction boxes, they can be easily accessed for troubleshooting or for adding additional fixtures.

Installation Guide

Extend one cable to the center of a lighting zone and install a junction box hub there. From the junction box hub, connect separate wires out to each fixture. The purpose is to provide a compartment for the splices. A spider splice is comprised of one main cable connected to the hub, and many cables branching out toward each landscape lighting fixture.landscape lighting T

Layout Tips

TIP #1

Lower loads per run mean lower voltage drop. Break your layout up 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 and use two junction box hubs.


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 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 ft from the transformer on the same run as a fixture 80 ft 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 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 and lead to shorter lamp life.

TIP #3

Don't Daisy Chain fixtures with Halogen Lamps. In other words, for fixtures with halogen lamps, don't connect fixture after fixture in-line to the same cable. You can do a couple fixtures in a 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. Of course, with LEDs the daisy chain method is fine because their voltage range is broad. Still, many designers continue to use junction boxes for the other benefits listed above.

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 ft 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.

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