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This article was posted 03/31/2006 and is most likely outdated.

Grounding vs Bonding: 250.92 Service Bonding

March 31, 2006

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PART V. BONDING

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Sections

250.92 Service Bonding.

(A) Equipment and Raceways. The following metal parts must be service bonded to an effective ground-fault current path in accordance with 250.92(B): Figure 250–125

(1) Metal raceways containing service conductors.
(2) Enclosures containing service conductors.

Author’s Comment: Metal raceways and enclosures containing service conductors must be effectively bonded in accordance with 250.92(B).

(3) A metal raceway containing the grounding electrode conductor.

Author’s Comments:
• The metal raceway containing the grounding electrode conductor must be effectively bonded in accordance with 250.64(E).
• Raceways or enclosures containing feeder and branch-circuit conductors are not required to be service bonded in accordance with 250.92(B). Figure 250–126

(B) Methods of Bonding. Enclosures and raceways containing service conductors must be bonded to an effective ground-fault current path by one of the following methods:

(1) Grounded Neutral Conductor. Enclosures and raceways containing service conductors are considered bonded to an effective ground-fault current path by bonding to the grounded neutral service conductor via the main bonding jumper. Figure 250–127
The bonding must be by exothermic welding, listed pressure connectors, listed clamps, or other listed
fittings [250.8].

Author’s Comments:
• A main bonding jumper is required to bond the service disconnect to the grounded neutral service conductor [250.24(B) and 250.28].
• At service equipment, the grounded neutral service conductor is used to provide the effective ground-fault current path to the power source [250.24(C)]. Therefore, an equipment grounding (bonding) conductor isn’t required to be installed within a nonmetallic raceway containing service-entrance conductors [250.142(A)(1) and 352.60 Ex. 2]. Figure 250–128

Figure 250–125
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Figure 250–126
(Click on image to enlarge)

Figure 250–127
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Figure 250–128
(Click on image to enlarge)

Comments

Can you tell me what grounding is required for a mobile lift that will be placed in psoition or wekks or months at a time, and runs off of 12 VDC power? The lift raises a camera in the sky, and stands 40 feet high. Are there requirements for a non-conductive section of the structure?

Phil Buckley

Reply from: Tara Moffitt
Phil, Questions of a technical nature should be posted on our code forum. You can post this question under the Grounding and Bonding topic and I'm sure you'll get some feedback. Here is the link to the code forum: http://www.mikeholt.com/codeForum/ Thank you

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