The Electrical Tool Store - Electrical Wiring Tools, Coax Cable Installation Tools and Phone & Data Wiring Tools
 

Top

Minimum Depth Requirements for Installing Underground Electrical Circuits

February 11, 2007

Buried Electric

 

 

Before you begin any underground electrical wiring project, you must first get a locate to find out what is underground. To schedule a locate call 811 in all 50 states and you will be connected to your local locator service.

Now that the locate is done, you need to determine which wiring method you will use. Are you going to install direct burial wire or cable? Perhaps you will use rigid metallic conduit or PVC. They all have different cover requirements.

For installations in a trench below 2 inches (50mm) thick concrete or equivalent:

  • Direct Burial Cables or Conductors need to be 18 inches (450mm) deep
  • Rigid Metal Conduit or Intermediate Metal Conduit need to be 6 inches (150mm) deep
  • Nonmetallic Raceways Listed for Direct Burial Without Concrete Encasement or Other Approved Raceways need to be 12 inches (300mm) deep
  • Residential Branch Circuits Rated 120 Volts or Less with GFCI Protection and Maximum Overcurrent Protection of 20 Amperes need to be 6 inches (150mm) deep
  • Circuits for Control of Irrigation and Landscape Lighting Limited to Not More Than 30 Volts and Installed with Type UF or in Other Identified Cable or Raceway need to be 6 inches (150mm) deep

For installations under a minimum of 4 inches (102mm) thick concrete exterior slab with no vehicular traffic and the slab extending not less than 6 inches (152mm) beyond the underground installation:

  • Direct Burial Cables or Conductors need to be 18 inches (450mm) deep
  • Rigid Metal Conduit or Intermediate Metal Conduit need to be 4 inches (100mm) deep
  • Nonmetallic Raceways Listed for Direct Burial Without Concrete Encasement or Other Approved Raceways need to be 4 inches (100mm) deep
  • Residential Branch Circuits Rated 120 Volts or Less with GFCI Protection and Maximum Overcurrent Protection of 20 Amperes need to be 6 inches (150mm) deep for direct burial or 4 inches (100mm) deep in a raceway
  • Circuits for Control of Irrigation and Landscape Lighting Limited to Not More Than 30 Volts and Installed with Type UF or in Other Identified Cable or Raceway need to be 6 inches (150mm) deep

For installations under streets, highways, roads, alleys, driveways, and parking lots:

  • Direct Burial Cables or Conductors need to be 24 inches (600mm) deep
  • Rigid Metal Conduit or Intermediate Metal Conduit need to be 24 inches (600mm) deep
  • Nonmetallic Raceways Listed for Direct Burial Without Concrete Encasement or Other Approved Raceways need to be 24 inches (600mm) deep
  • Residential Branch Circuits Rated 120 Volts or Less with GFCI Protection and Maximum Overcurrent Protection of 20 Amperes need to be 24 inches (600mm) deep
  • Circuits for Control of Irrigation and Landscape Lighting Limited to Not More Than 30 Volts and Installed with Type UF or in Other Identified Cable or Raceway need to be 24 inches (600mm) deep

For installations under one- and two-family dwelling driveways and outdoor parking areas, and used only for dwelling-related purposes:

  • Direct Burial Cables or Conductors need to be 18 inches (450mm) deep
  • Rigid Metal Conduit or Intermediate Metal Conduit need to be 18 inches (450mm) deep
  • Nonmetallic Raceways Listed for Direct Burial Without Concrete Encasement or Other Approved Raceways need to be 18 inches (450mm) deep
  • Residential Branch Circuits Rated 120 Volts or Less with GFCI Protection and Maximum Overcurrent Protection of 20 Amperes need to be 12 inches (300mm) deep
  • Circuits for Control of Irrigation and Landscape Lighting Limited to Not More Than 30 Volts and Installed with Type UF or in Other Identified Cable or Raceway need to be 18 inches (450mm) deep

For installations under a building:

  • Direct Burial Cables or Conductors need to be 0 inches (0mm) deep (in raceway only)
  • Rigid Metal Conduit or Intermediate Metal Conduit need to be 0 inches (0mm) deep
  • Nonmetallic Raceways Listed for Direct Burial Without Concrete Encasement or Other Approved Raceways need to be 0 inches (0mm) deep
  • Residential Branch Circuits Rated 120 Volts or Less with GFCI Protection and Maximum Overcurrent Protection of 20 Amperes need to be 0 inches (0mm) deep (in raceway only)
  • Circuits for Control of Irrigation and Landscape Lighting Limited to Not More Than 30 Volts and Installed with Type UF or in Other Identified Cable or Raceway need to be 0 inches (0mm) deep (in raceway only)

For all installations not specified above:

  • Direct Burial Cables or Conductors need to be 24 inches (600mm) deep
  • Rigid Metal Conduit or Intermediate Metal Conduit need to be 6 inches (150mm) deep
  • Nonmetallic Raceways Listed for Direct Burial Without Concrete Encasement or Other Approved Raceways need to be 18 inches (450mm) deep
  • Residential Branch Circuits Rated 120 Volts or Less with GFCI Protection and Maximum Overcurrent Protection of 20 Amperes need to be 12 inches (300mm) deep
  • Circuits for Control of Irrigation and Landscape Lighting Limited to Not More Than 30 Volts and Installed with Type UF or in Other Identified Cable or Raceway need to be 6 inches (150mm) deep

I don’t believe that I need to explain how to install your conduit or cable from point A to point B. However, I may be able to offer some tips.

Tip # 1 - When installing PVC conduit, it is easiest to glue your conduit together before you place it in the ditch.

Tip # 2 - When you place the PVC conduit in the ditch, be sure the bottom of the ditch is fairly level. If there are large rocks or deep valleys in certain spots, when you backfill, the PVC will pull apart at the nearest coupling. This defeats the purpose of installing the conduit in the first place.

DIY Electrical Wiring Help from a Master Electrician Do you need assistance with your electrical wiring project? Please visit my DIY Electrical Wiring Help from a Master Electrician page. Where I provide electrical wiring tips, expert electrical advice, answers to your electrical questions and electrical consulting & design services over the phone, via instant messenger or via email.

If you enjoyed this post, make sure you subscribe to my RSS feed or receive updates via email. You can also follow me on Twitter and "LIKE" me on Facebook.

Similar Posts:
Site Sponsor
The Electrical Tool Store - Your online source for electrical wi


Comments

7 Responses to “Minimum Depth Requirements for Installing Underground Electrical Circuits”

  1. E. Diehl on September 25th, 2007 9:32 pm

    What are some ways to get a “pull cord” 300 ft. throught 3″ PVC Conduit? We are doing our own underground conduit in advance of the Elect. Co. putting in a Primary feed from street. We must supply a “pull tape” or other suitable strong “cord” for them to attach the Primary power cable, and then, for them to pull their entire cable throught to the new Ground level Transformer. Someone mentioned using a Shop Vac and a plastic bag tied to end of cord. Can you help describe these steps or are there other ways? Thanks, E. Diehl

  2. John Lind on March 26th, 2010 10:10 am

    Requirements for depth (if any) for communications cables such as telephone in streets and roadways..

  3. keligi on April 14th, 2011 12:58 pm

    1.What are the rule and regulation on installation on underground electrical line and main waterline?
    2. We are planning to install a 6″waterline and the plans call for a underground electrical line to run under our waterline 1′ separation. Is this allow in the rules and regulation?

  4. Jackie Sandoval on May 2nd, 2011 6:05 pm

    Can you provide the references used for these depths? Are they based off the NEC?

  5. Larry Billups on July 12th, 2011 11:30 am

    I have a 220 volt airconditioner installed in my sunroom. I see the 220 volt line go straight from the wall into my yard and as far as I can tell it is just a vinyl gray colored molded wire with no conduit. Is this OK per code?

  6. jim on August 17th, 2011 2:31 pm

    what min depth should a phone line be in conduit in a back yard

  7. Tre LaDormin on January 29th, 2012 1:52 pm

    Regarding the minimum depth requirements, can you cite the applicable NFPA 70 NEC code chapter/paragraphs/sections? I’m writing a short paper on direct burial vs buried conduit. I keep getting conflicting depth answers but everyone claims they are correct per NEC. I’m looking at concrete encased raceway &/or rigid (PVC or metalllic) in an area of solid rock(limestone) and would like to avoid trenching. The run would be less than 600 volts, three phase with ground and neutral conductors. Thanks for your help!

Do you have a question or idea to add to this post? Feel free to post it below. Due to a large backlog and an overwhelming response, it takes approximately 30 days to receive an answer to your electrical question for free. Simply subscribe to this blog (use one of the subscription methods listed in the top right corner of this page) and your answer will be listed in a new blog post in the near future.

To receive an immediate answer (in less than 24 hours) please visit my DIY Electrical Wiring Help from a Master Electrician page.






seven − = 3

Bottom