How to Safely Bury Underground Wiring for Outdoor Lighting

Introduction

Installing underground wiring for outdoor lighting can greatly enhance the look and feel of your yard or outdoor space. However, it's important to bury the wiring properly to ensure safety and prevent damage. In this guide, I will walk through the complete process of burying underground wiring for outdoor lighting and provide tips to do it safely.

Planning the Wiring Route

The first step is to plan out the wiring route. Make a simple map of where you want to install the outdoor lighting and trace the path where you will bury the wire.
Consider the locations of existing utility lines. You'll need to bury the wiring at least 12-18 inches away from any other underground utilities to prevent damage.
Account for any hardscaping or structures like patios, trees, or gardens. Try to find the most direct route that avoids having to dig under permanent structures.
Measure the total distance to determine how much wire you'll need. Add about 10% extra as a buffer.

Choosing the Right Outdoor Wire

For most outdoor lighting projects, direct burial cable is the best type of wire to use. It has a tough polyethylene jacket that stands up to being underground.
12/2 landscape lighting cable is a common size, with 12 gauge wire and 2 insulated conductors. Use a thicker 10 gauge wire for runs longer than 100 feet.
UF-B wire is another direct burial option that can be used for connecting outdoor lighting to the main circuit panel.
Make sure to get wire rated for wet locations and outdoor use. Do not use standard indoor electrical wire.

Digging the Underground Trench

Dig a trench along your planned route using a shovel or trencher. The trench should be 6-12 inches deep and 4-6 inches wide.
If digging near utility lines, dig very carefully with a shovel once you reach around 18 inches down. Use a wire detector to avoid buried wires.
Slope the bottom of the trench slightly to allow drainage and prevent water pooling on the wire.
Make gradual sweeps with the trench at any corners rather than 90 degree angles. This makes pulling the wire easier.

Burying and Protecting the Wire

Carefully lay the wire into the bottom of the trench. Avoid kinking or over-bending the wire.
For extra protection, you can lay the wire inside non-metallic conduit or a protective sleeve, but it is not required for most outdoor lighting.
Every 3-4 feet, secure the wiring to the bottom of the trench using landscape staples designed for underground use.
Before backfilling, run a final inspection to make sure the wiring is positioned correctly in the trench.

Backfilling and Completing the Installation

Use the soil removed from digging to backfill and cover the trench. Pack it down firmly every 6 inches to remove air pockets.
For the final 4-6 inches, use soil without rocks to avoid damaging the wire insulation. Tamp it down with the backside of a shovel.
At the ends, leave access boxes or coils of extra wire for connections to fixtures and the power source. Secure with wire nuts or waterproof connectors.
Test the wiring before burying the access points and installing your lights. Make any above ground connections you need.
Restore planting beds, sod, hardscapes etc to their original appearance. Aim to make the burial area minimally invasive.

Safety Tips

Always turn off power at the circuit breaker before starting. Verify power is off with a contact voltage tester.
Call 811 for utility marking if digging near potential utility lines. Respect their markings.
Use fiberglass handles for shovels and tools when working around potential underground power.
Wear work gloves when handling wire. Watch for sharp rocks or tools that could damage the wire jacket.
Keep children and pets away from the work area to avoid tripping hazards or tools being knocked into the trench.

By following these guidelines, you can successfully run underground wiring for outdoor lights in a safe manner that meets electrical code. Take it slow, bury the wire carefully, and use the right materials to ensure your wiring lasts for many years underground.