Code Change Summary: New footnotes appear under Table 300.5.

NEC Table 300.5 provides minimum cover requirements for wiring methods and raceways from zero to 1000 volts. There is a common misconception that spare, unused raceways and low voltage installations are exempt from the requirements in the table. The simple fact that the table covers installations starting at zero volts says otherwise.

It is important to remember that minimum cover and minimum trench depth are not the same. According to note 1 under the table, cover is defined as the shortest distance in inches 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. In order to get the proper cover over the top of the wiring method, the overall depth of the trench will need to be deeper than the minimum cover requirements.

Column 5 of Table 300.5 provides the cover depth for irrigation and landscape lighting circuits operating at 30 volts or less and installed using UF cable or other identified cables or raceways. Unless covered by concrete or installed directly under a building, the minimum cover depth in column 5 is six inches.

In some cases, the manufacturer furnishes the wiring method for the lighting kit which may include cables that are not intended for direct burial outdoors but may be suitable for indoor installations just under the top soil or bark in an above grade planter box. For these listed lighting systems, the installation instructions will specify if the wiring method can be buried at all and if so, the minimum or maximum required burial depth.

In the 2017 NEC^®, two new footnotes were added to specifically address listed low-voltage lighting systems:

• Footnote A allows a lesser depth than permitted in column 5 where specified in the installation instructions of a listed low-voltage lighting system.
• Footnote B allows a depth of 6 inches for pool, spa, and fountain lighting, installed in a nonmetallic raceway, limited to not more than 30 volts where part of a listed low-voltage lighting system.

Below is a preview of Article 300. See the actual NEC^® text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the 2017 NEC^® edition of NFPA 70.