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What's Wrong Here?

Jun 5, 2008 1:15 PM, By Joe Tedesco, NEC Columnist

Timothy Thomas, manager/chief inspector, Commonwealth Electrical Inspection Service, Inc., New York State, couldn’t believe it when he saw this one. “They did not even call for a stake out,” says Thomas.

Was the required warning ribbon in place when the digging began for this pool or not? There are several requirements of 300.5 (Underground Installations) that are worth taking note of for this particular installation.

• 300.5(A) Minimum Cover Requirements. “Direct-buried cable or conduit or other raceways shall be installed to meet the minimum cover requirements of Table 300.5.”
• 300.5(D) Protection from Damage. “Direct-buried conductors and cables shall be protected from damage in accordance with 300.5(D)(1) through (D)(4).”
• 300.5(D)(1) Emerging from Grade. “Direct-buried conductors and cables emerging from grade and specified in columns 1 and 4 of Table 300.5 shall be protected by enclosures or raceways extending from the minimum cover distance below grade required by 300.5(A) to a point at least 2.5 m (8 ft) above finished grade. In no case shall the protection be required to exceed 450 mm (18 in.) below finished grade.”
• 300.5(D)(2) Conductors Entering Buildings. “Conductors entering a building shall be protected to the point of entrance.”
• 300.5(D)(3) Service Conductors. “Underground service conductors that are not encased in concrete and that are buried 450 mm (18 in.) or more below grade shall have their location identified by a warning ribbon that is placed in the trench at least 300 mm (12 in.) above the underground installation.”
• 300.5(D)(4) Enclosure or Raceway Damage. “Where the enclosure or raceway is subject to physical damage, the conductors shall be installed in rigid metal conduit, intermediate metal conduit, Schedule 80 PVC conduit, or equivalent.”

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