Grounding vs Bonding Online Training

This article was posted 03/17/2006 and is most likely outdated.

Grounding vs Bonding: 250.86 Other Enclosures

March 17, 2006

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PART IV. GROUNDING (BONDING) OF ENCLOSURE, RACEWAY, AND SERVICE CABLE

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250.86 Other Enclosures.

Metal raceways and enclosures containing electrical conductors that operate at over 50V [250.112(I)] must be grounded (bonded) to an effective ground-fault current path [250.4(A)(5)].

Author’s Comment: Metal raceways and metal enclosures containing circuit conductors from electrical supply sources that operate at 50V or less aren’t required to be grounded [250.86]. For example, metal boxes used with power-limited fire alarm circuits operating at 50V or less aren’t required to be grounded.

Exception 2: Short sections of metal raceways used for the support or physical protection of cables aren’t required to be grounded (bonded) to an effective ground-fault current path. Figure 250–123

Author’s Comment: NM cable on a wall of an unfinished basement installed, in a listed metal raceway, must be grounded to an effective ground-fault current path [334.15(C)].

Exception 3: Metal elbows having 18 in. or more of earth cover aren’t required to be grounded (bonded) to an effective ground-fault current path. Figure 250–124

Figure 250–123
(Click on image to enlarge)

Figure 250–124
(Click on image to enlarge)

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