NEC Art 250.24 (A)(4) Grounding Service Supplied Alternating Current Systems

[Grendal]

In this paragraph it states "the grounding electrode conductor shall be permitted to be connected to the equipment grounding terminal bar, or bus to which the main bonding jumper is connected." Is this correct?

It is my understanding that the ground electrode conductor should be connected to the grounded conductor terminal bar or bus and that the grounded terminal bar or bus is bonded with the equipment terminal bar or bus.

 

[Gregg Harris]

In this paragraph it states "the grounding electrode conductor shall be permitted to be connected to the equipment grounding terminal bar, or bus to which the main bonding jumper is connected." Is this correct?

It is my understanding that the ground electrode conductor should be connected to the grounded conductor terminal bar or bus and that the grounded terminal bar or bus is bonded with the equipment terminal bar or bus.

(4) Main Bonding Jumper as Wire or Busbar. Where the main bonding jumper specified in 250.28 is a wire or busbar and is installed from the grounded conductor terminal bar or bus to the equipment grounding terminal bar or bus in the service equipment, the grounding electrode conductor shall be permitted to be connected to the equipment grounding terminal, bar, or bus to which the main bonding jumper is connected.

 

[Smart $]

... Is this correct?

What the Code states is always correct.

 

[Grendal]

In the 2011 NEC handbook Exhibit 250.1, 250.11, 250.17, 250.20, 250.22, 250.28, 250.29 250.31, and 250.52 all show the grounding electrode conductor being connected to the grounded conductor terminal bus. It is not connected to the equipment terminal bus.

 

[Smart $]

In the 2011 NEC handbook Exhibit 250.1, 250.11, 250.17, 250.20, 250.22, 250.28, 250.29 250.31, and 250.52 all show the grounding electrode conductor being connected to the grounded conductor terminal bus. It is not connected to the equipment terminal bus.

250.24(A)(1) states where the GEC is required to be connected. 250.24(A)(4) is, in essence, a conditional exception to (A)(1), noting the usage of the word permitted.

 

[infinity]

If the main bonding jumper is a screw, like in a residential panel then you must use the neutral bus. If the MBJ is made of bus or is a wire conductor, like in a large switchboard then you can terminate the GEC on either bus.