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This article was posted 03/31/2006 and is most likely outdated.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
(Click on image to enlarge)

Figure 250–126
(Click on image to enlarge)

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

Comments

In Figure 250-125 there appears to be an uninsulated split-bolt connector on each of the 3 service wires feeding the meter on the right. What is the reason for this? It would make for a less problematic installation if each of the 3 wires were run unbroken from the distribution terminal block in the raceway to the respective terminal on the meter socket.

Denny M

Reply from: Mike Culbreath
Denny, I agree with your opinion that it would be a "better" installation without the splices althought it does comply with the NEC [230.46]. The only reason the splices are in this graphic is because I used this service in another location where they were revelent to the point being made. Since the splices do not add any specific value to this graphic in this location, I will remove them. Thanks for your input.

Mike Culbreath Technical Illustrator Mike Holt Enterprises, Inc.

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