Direct Burial Transformer 12 & 24 Volts
General Notes
Be certain your transformer is the proper wattage. The best way to do this is to use
the Unique Lighting Load Calculation Form or the Unique Lighting exclusive Wiring
Wizard software. To order a complementary copy of the Wiring Wizard, call us at 1800-955-4831.
Transformer Location and Mounting Instructions
1. Select an appropriate location to install your Direct Burial transformer. The Direct Burial units will
need to have primary power brought to each unit.
2. Be sure to locate the transformer in an area that it will not be damaged by service vehicles or
maintenance crews.
3. Dig the appropriate sized hole to accommodate the box size and allow the lid to be approximately
1” above grade for easy access. A good tip is to use an over sized valve box and install the Direct
Burial transformer inside the valve box then fill the inside of the valve box with gravel. This will
give the Direct Burial added protection and the gravel is a clean back fill material.
4. The Direct Burial comes with 4 flat sides. These flat sides are where the primary and secondary
runs enter the box. Before drilling any entry holes make sure the unit is positioned correctly.
There is a divider between the primary and secondary wiring. Make sure the primary (small
compartment) is on the same side as the primary power input.
5. Drill all holes into box ½” above the reveal in the box. Make sure the top of the elbow is above the
green wax line.
6. Pull in primary and wire to pigtail inside the primary compartment. Make connections. Make sure
primary power is
before making connections.
7. Pull in all secondary connections.
Low Voltage Cable Connections
1. After all fixtures have been placed and Hubs have been connected, gather all Homerun wires at
the transformer.
2. Separate each cable (approx. 6”) and strip off 1” of the insulation.
Volt Testing
1. Connect the secondary wires to the 12 / 24 volt wire tap.
2. Once all connections have been made, turn transformer on.
3. All the lights should turn on. Using your digital volt meter, check the voltage at each Hub.
4. Make a note of each Hub’s voltage and proceed with adjusting the voltage at the transformer.
Proper Voltage
Polarity is not a problem with low voltage lighting. The wire is marked with the ratings on one leg
and ribbed texture on the other leg. Make sure one leg is attached to the common and the other is
attached to the voltage output tap.
The ideal voltage for a 12 volt halogen lamp is between 10.8 and 12 volts. The ideal voltage for a 24 volt
halogen lamp is between 21.6 and 24.0 volts. Too much voltage will shorten the lamp life. Too little
voltage may produce a yellowish, dim light.
1. If the volt meter reads 9 volts, you will need to add 3 volts at the transformer to compensate for
the voltage drop. You would need to connect this Homerun wire to the 15 volt tap wire since 12
volts plus 3 volts equals 15 volts. (The idea is to have 12 volts at the Hub).
2. Disconnect the Homerun wire from the 12 volt tap wire and reconnect to the 15 volt tap.
3. Follow the same procedure for each Homerun wire remaining.
4. 24 volt systems follow the same steps.
Waxing the unit.
After every step has been completed and the voltage is correct at all hubs, the unit is ready to be sealed
with wax. The wax acts like water when melted and will find every path out of the can. Use the Duct Seal
to seal around all entry points into the transformer. Take your time and make sure everything is sealed
properly. Press the putty into all conduit openings sealing them the best you can. Place primary power
connections at the lowest point in the primary compartment. Place secondary wire connections at the
lowest point in the secondary compartment. The primary and secondary divider plate has holes in it to
allow wax to flow from one compartment to another. Each Direct Burial comes with three pounds of wax.
Heat the wax using a camping style stove with pan or coffee pot. Pour the wax into the box while making
sure your connections are below the wax line. Make sure the PRIMARY FUSE is above the wax line. If
using secondary fusing, make sure it is above the wax line. Leave a service loop out of the wax for the
primary and secondary. This will allow fixtures to be added in the future. Leave lid off to allow wax to cure.
After this process is done you can install the lid.
Multiple Connections At Each Tap
You may use the various voltage taps as often as needed. Example: If you need to use a volt tap two
times, simply connect both cables to the volt tap. However, we do recommend that you limit the
amperage on any single tap to a maximum of 30 amps.