How to Safely Bury Electrical Wires for Outdoor Lighting

Introduction

Installing outdoor lighting can greatly enhance the beauty and functionality of your home's exterior. However, it requires safely running electrical wires underground from your home's electrical panel to the desired lighting fixtures. Improperly buried wires can pose serious safety hazards, so follow these steps to bury electrical wires properly for outdoor lighting.

Gather the Required Materials

You will need:

Direct burial electrical cable - This wire is rated for direct underground installation. Romex and other standard indoor wiring cannot be buried.
Outdoor electrical boxes - Required for splicing wires and mounting fixtures. Use boxes rated for wet locations.
Conduit - Optional to protect wire runs. Use schedule 40 PVC or rigid metal conduit.
Trenching shovel - For efficiently digging a trench to bury the wires. A standard shovel can also work.
Gloves - Protect your hands when handling cables and materials.
Tape measure - To measure trench depth and wire runs.
PVC cement and primer - For gluing conduit connections if using.

Dig the Trench

Dig a trench from your home's exterior wall to each desired lighting fixture location. Here are key tips for digging:

Dig the trench 12-18 inches deep. This protects the wiring from accidental digging in the future.
Make the trench 6-12 inches wide. Wide enough to work in but not excessively wide.
Avoid utility lines. Call 811 before digging for them to mark any underground utilities.
Slope the trench towards fixtures, if possible, to prevent moisture buildup.
If digging near existing structures like sidewalks or walls, hand dig carefully to avoid damage.

Run the Electrical Cable

Now you can lay the electrical cable in the trench:

Use direct burial cable rated for wet/damp locations. Do not use standard Romex.
Provide a 6-12 inch loop of extra cable at each end to allow splicing.
For straight wire runs exceeding 200 feet, it is advisable to use 10 AWG wire for better voltage drop.
For added protection, run wires through conduit. Glue conduit joints with PVC cement.
For multiple wire runs, keep them spaced apart in the trench or use divider strips.

Prepare the Wiring End Points

Install outdoor electrical boxes at each end:

Mount a weatherproof box on the exterior wall near the home's electrical panel.
Ground the box according to local codes for safety.
Install boxes where fixtures will be located. Elevate above ground level if in a wet area.
Connect conduit ends to the electrical boxes, if using.

Backfill and Compact the Trench

Once wiring is laid out, backfill the trench with soil:

Partially backfill to cover wires, then hand compact with tamper to avoid damaging wires.
Fill the trench fully, compacting in layers to within 2-3 inches of grade.
Avoid pouring in soil rapidly or running heavy machinery over trench.
Mound remaining soil over trench and allow natural settling.

Splice Wires and Mount Fixtures

The final steps are to connect the wiring:

In the exterior wall box, use wire nuts to splice cable to existing home wiring.
At fixture boxes, connect cable and mount the light fixtures.
Allow enough excess wire (6-12 inches) for splices.
Use exterior rated wire nuts and electrical tape for waterproof splices.
Consult wiring diagrams for proper connections of multiple fixtures.

Following these key steps will allow you to safely run underground electrical wires for outdoor lighting. Take care when burying cables, splicing connections, and mounting fixtures to ensure a safe and functional outdoor lighting system.

Conclusion

Burying electrical wiring properly is crucial for outdoor lighting safety and functionality. By using the right materials, carefully digging the trench, running direct burial cables, backfilling properly, and making waterproof splices, you can create an outdoor lighting system that will last for years to come. Be sure to call 811 before digging, follow local codes, and use extreme care when working with electrical systems. With the right precautions, burying wires can expand your home's livable space and ambiance into the outdoors for all to enjoy.