Electrical Codes for Underground Wiring

By Dave Rongey
Summary: Listing of electrical codes for underground with examples of electrical underground codes for home electrical wiring.

Electrical Code Definitions for Underground Home Electrical Wiring

UNDERSTANDING THE IMPORTANCE OF PROPER UNDERGROUND WIRING

NEC 300-3

All conductors of the same circuit, including grounded conductors, shall be contained in the same raceway, cable, or trench.

Code Adoption Information:
The codes shown are examples only and may not be current or accurate for your application or jurisdiction. Contact your local building authority for complete information.
NATIONAL ELECTRICAL CODE

NEC 300-5 Generally, cables approved for direct burial shall have a minimum cover of 24 inches. When wiring is installed at dwellings in approved non-metallic raceways, the minimum cover can be reduced to 18 inches.

NEC 300-5 GFCI When a GFCI protected residential branch circuit is rated 20 amps or less and 120 volts or less, the minimum cover can be reduced to 12 inches.

NEC 300-5 Conductors emerging from underground shall be installed in rigid metal conduit, intermediate metal conduit, or Schedule 80 rigid nonmetallic conduit to provide protection from physical damage. This protection shall extend from 18 inches below grade or the minimum cover distance, above, to the point of termination above ground.

Residential Electrical Code Examples for Underground

NEC 300.5 Underground Wiring
Conduit Identification Underground service laterals shall have their location identified by a warning ribbon placed in the trench at least 12 inches above the underground installation.

NEC 300.5 Underground Wiring conduit movement protection Where subject to movement, direct buried cables or raceways shall be arranged to prevent damage to the enclosed conductors or connected equipment;

NEC 300.5 Underground Wiring Conduits emerging from the ground Conductors emerging from underground shall be installed in rigid metal conduit, intermediate metal conduit, or Schedule 80 rigid nonmetallic conduit from 18 inches below grade or the minimum cover distance to the point of termination above ground.

Always contact your local building authority for complete and up to date code information.

More about Electrical Codes for Underground Electrical

« Electrical Codes for Grounding

Electrical Codes for Home Wiring »

Questions about Electrical Codes for Underground Wiring

Questions about Residential Electrical Wiring Codes for Underground Wiring

Question from Joshua, a Student from Kansas City, Missouri.

What is the underground service entrance conduit fitting called that would absorb shock?

The inspector said I needed some sort of fitting to attach to the conduit of my underground service entrance that would absorb shock if the house should ever come off of its foundation. This device would ensure that my conduit and wires didn’t shift as well and prevent potential damage. What is this fitting called?

Dave’s Answer:

I believe the inspector is describing an Expansion Joint, as referred to in NEC Article 300.5(J) Expansion Joint. The article also explains how cables shall be arranged so as to prevent damage to the enclosed conductors.


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Home Electrical Wiring - Room by Room
Wiring 120 and 240 Volt Circuits
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Grounding and Bonding
55 Electrical Code Topics
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11 Home Wiring Plans
28 Wiring Diagrams and Illustrations
Illustrated Wiring Methods
NEC Codes for Home Electrical Wiring
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Electrical Tip

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The Non-Contact Electrical Tester
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Electrical Code Questions and Answers