|
Table 300.5 Minimum Cover Requirements, Nominal Burial in Millimeter
(Inches) |
|
Type of Wiring Method or Circuit |
|
|
Column 1 |
Column 2 |
Column 3 |
Column 4 |
Column 5 |
|
Direct Burial Cables or Conductors |
Rigid Metal Conduit or Intermediate
Metal Conduit |
Nonmetallic Raceways Listed for
Direct Burial Without Concrete Encasement or Other Approved Raceways |
Residential Branch Circuits Rated
120 Volts or Less with GFCI Protedtion and Maximum Overcurrent
Protection of 20 Amperes |
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 |
|
Location of Wiring Method or |
mm |
in. |
mm |
in. |
mm |
in. |
mm |
in. |
mm |
in. |
|
Circuit |
|
All locations not specified below |
600 |
24 |
150 |
6 |
450 |
18 |
300 |
12 |
150 |
6 |
|
|
|
|
|
|
In trench below 50-mm (2-in.) thick
concrete or equivalent |
450 |
18 |
150 |
6 |
300 |
12 |
150 |
6 |
150 |
6 |
|
|
|
|
|
|
|
Under a building |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
|
(in raceway only) |
|
|
(in raceway only) |
(in raceway only) |
|
Under minimum of 102-mm (4-in.) |
450 |
18 |
100 |
4 |
100 |
4 |
150 |
6 |
150 |
6 |
|
thick concrete exterior slab with no |
|
|
|
(direct burial) |
|
|
vehicular traffic and the slab |
|
|
|
|
|
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extending not less than 152 mm (6 in.) |
|
|
|
100 |
4 |
|
|
beyond the underground installation |
|
|
|
(in raceway) |
|
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|
|
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Under streets, highways, roads, |
600 |
24 |
600 |
24 |
600 |
24 |
600 |
24 |
600 |
24 |
|
alleys, driveways, and parking |
|
|
|
|
|
lots |
|
|
|
|
|
One- and two-family dwelling |
450 |
18 |
450 |
18 |
450 |
18 |
300 |
12 |
450 |
18 |
|
driveways and outdoor |
|
|
|
|
|
parking areas, and used only |
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|
|
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for dwelling-related purposes |
|
|
|
|
|
In or under airport runways, |
450 |
18 |
450 |
18 |
450 |
18 |
450 |
18 |
450 |
18 |
|
including adjacent areas |
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where trespassing prohibited |
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Notes: |
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1.
Cover is defined as the shortest distance in
millimeters (inches) measured between a point on the top surface of
any direct-buried conductor, cable, conduit, or other raceway and the
top surface of finished grade, concrete, or similar cover. |
2.
Raceways approved for burial only where concrete
encased shall require concrete envelope not less than 50 mm
(2 in.)
thick. |
|
3.
Lesser depths shall be permitted where cables and
conductors rise for terminations or splices or where access is
otherwise required. |
|
4.
Where one of the wiring method types listed in
Columns 1–3 is used for one of the circuit types in Columns 4 and 5,
the shallowest depth of burial shall be permitted. |
5.
Where solid rock prevents compliance with the
cover depths specified in this table, the wiring shall be installed in
metal or nonmetallic raceway permitted for direct burial. The raceways
shall be covered by a minimum of 50 mm
(2 in.) of concrete extending
down to rock. |
