minimum cover

[novemberaudi]

What is the minimum cover requirement for non metallic conduit under the floor of a parking garage that has a 5 inch thick slab on grade?

300.5 column 3 reads 1) 12 inches if under 2 inches of concrete, 2) 0 inches if under a building, 3) 24 inches if under driveways and parking lots.

Also a second question, what is the required depth for the GEC that goes between 2 ground rods driven 6 feet apart?

 

[ritelec]

interesting question

 

[iwire]

What is the minimum cover requirement for non metallic conduit under the floor of a parking garage that has a 5 inch thick slab on grade?

300.5 column 3 reads 1) 12 inches if under 2 inches of concrete, 2) 0 inches if under a building, 3) 24 inches if under driveways and parking lots.

I would call a parking garage a building but I would likely talk to the inspector first.

Also a second question, what is the required depth for the GEC that goes between 2 ground rods driven 6 feet apart?

0"

 

[Smart $]

I would call a parking garage a building but I would likely talk to the inspector first. ...

I agree. I don't believe the intent of the "Under a building" condition was meant to include one in which there would be vehicular traffic on the lowest level. My guess is the AHJ will err to the side of caution and require the same cover as parking lots.

 

[kwired]

I agree. I don't believe the intent of the "Under a building" condition was meant to include one in which there would be vehicular traffic on the lowest level. My guess is the AHJ will err to the side of caution and require the same cover as parking lots.

then we ask him how much cover is necessary on the upper levels

 

[novemberaudi]

Thanks for the responses.

 

[petersonra]

What is the minimum cover requirement for non metallic conduit under the floor of a parking garage that has a 5 inch thick slab on grade?

300.5 column 3 reads 1) 12 inches if under 2 inches of concrete, 2) 0 inches if under a building, 3) 24 inches if under driveways and parking lots.

is a parking garage a building?

Also a second question, what is the required depth for the GEC that goes between 2 ground rods driven 6 feet apart?

what difference does it make how far apart they are? they could be two feet apart or 50 feet apart and the answer is still the same - zero.

 

[GoldDigger]

Also a second question, what is the required depth for the GEC that goes between 2 ground rods driven 6 feet apart?

As long as it is not exposed to physical damage (and is not a tripping hazard!) no cover at all is required.

 

[infinity]

As long as it is not exposed to physical damage (and is not a tripping hazard!) no cover at all is required.

I agree, but where is the part about physical damage in the NEC?

I attempted to get the wording that no cover was required into the 2014 but the CMP rejected my proposal. They did comment that T300.5 does not apply.

3-39 Log #2733 NEC-P03 Final Action: Reject
(Table 300.5)
________________________________________________________________
TCC Action: The Correlating Committee directs this proposal be
forwarded to Code-Making Panel 5 for comment.
Submitter: Robert Meier, Norwood, NJ
Recommendation: Add text to read as follows:
Table 300.5 Minimum Cover Requirements, 0 to 600 Volts, Nominal,
Burial in Millimeters (Inches)
Notes:
1. Cover is defined as the shortest distance in millimeters (inches) measured
between a pint 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.
6. The information contained in this table shall not apply to grounding
electrode conductors or bonding jumpers.
Substantiation: Although grounding electrode conductors and bonding
jumpers are not required to meet the minimum cover requirements of this table
some inspectors have been requiring them to be installed as such. Their
(incorrect) interpretation of this table is that an individual grounding electrode
conductor or bonding jumper would fall under Column 1 which is for Direct
buried Cables or Conductors. The addition of this not the T300.5 will clarify
that the conductors listed in Column 1 are not grounding electrode conductors
or bonding jumpers.
Panel Meeting Action: Reject
Panel Statement: The scope of Article 300 covers wiring methods for all
wiring installations, unless modified by the other articles in Chapter 3. Article
300 and Table 300.5 would not apply to grounding electrode conductors and
bonding conductors installed from the grounding electrodes to the grounding
electrode, unless a wiring method provides physical protection as required by
250.64(E).
There certainly is not an issue of too much current or voltage on these
conductors or cable. However, protection of these important conductors and
cables are imperative. A ground ring grounding electrode, which is a conductor
or cable, is required to be buried at least 30 inches deep.
Adding a note, as recommended, could cause confusion relating to other
sections in other chapters of the NEC that are not directly related to wiring
methods with an implied burial depth based on Table 300.5.
Grounding electrode conductors and bonding jumpers are under the
jurisdiction of Code-Making Panel 5. Whether to apply Table 300.5 or not to
these applications must be decided by Code-Making Panel 5. Code-Making
Panel 3 recommends that this proposal be sent to Panel 5 for comment.
Number Eligible to Vote: 14
Ballot Results: Affirmative: 14