UpCodes logo
Go To Full Code Chapter
(A) Systems With a Grounded Conductor at the Service Point
Where an ac system is grounded at any point and is provided with a grounded conductor at the service point, a grounded conductor(s) shall be installed and routed with the ungrounded conductors to each service disconnecting means and shall be connected to each disconnecting means grounded conductor(s) terminal or bus. A main bonding jumper shall connect the grounded conductor(s) to each service disconnecting means's enclosure. The grounded conductor(s) shall be installed in accordance with 250.186(A)(1) through (A)(4). The size of the solidly grounded circuit conductor(s) shall be the larger of that determined by 250.184 or 250.186(A)(1) or (A)(2).
Exception: Where two or more service disconnecting means are located in a single assembly listed for use as service equipment, it shall be permitted to connect the grounded conductor(s) to the assembly common grounded conductor(s) terminal or bus. The assembly shall include a main bonding jumper for connecting the grounded conductor(s) to the assembly enclosure.
(1) Sizing for a Single Raceway or Overhead Conductor
The grounded conductor shall not be smaller than the required grounding electrode conductor specified in Table 250.102(C)(1) but shall not be required to be larger than the largest ungrounded service-entrance conductor(s).
(2) Parallel Conductors in Two or More Raceways or Overhead Conductors
If the ungrounded service-entrance conductors are installed in parallel in two or more raceways or as overhead parallel conductors, the grounded conductors shall also be installed in parallel. The size of the grounded conductor in each raceway or overhead shall be based on the total circular mil area of the parallel ungrounded conductors in the raceway or overhead, as indicated in 250.186(A)(1), but not smaller than 1/0 AWG.
Informational Note: See 310.10(G) for grounded conductors connected in parallel.
(3) Delta-Connected Service
The grounded conductor of a 3-phase, 3-wire delta service shall have an ampacity not less than that of the ungrounded conductors.
(4) Impedance Grounded Neutral Systems
Impedance grounded neutral systems shall be installed in accordance with 250.187.
(B) Systems Without a Grounded Conductor at the Service Point
Where an ac system is grounded at any point and is not provided with a grounded conductor at the service point, a supply-side bonding jumper shall be installed and routed with the ungrounded conductors to each service disconnecting means and shall be connected to each disconnecting means equipment grounding conductor terminal or bus. The supply-side bonding jumper shall be installed in accordance with 250.186(B)(1) through (B)(3).
Exception: Where two or more service disconnecting means are located in a single assembly listed for use as service equipment, it shall be permitted to connect the supply-side bonding jumper to the assembly common equipment grounding terminal or bus.
(1) Sizing for a Single Raceway or Overhead Conductor
The supply-side bonding jumper shall not be smaller than the required grounding electrode conductor specified in Table 250.102(C)(1) but shall not be required to be larger than the largest ungrounded service-entrance conductor(s).
(2) Parallel Conductors in Two or More Raceways or Overhead Conductors
If the ungrounded service-entrance conductors are installed in parallel in two or more raceways or overhead conductors, the supply-side bonding jumper shall also be installed in parallel. The size of the supply-side bonding jumper in each raceway or overhead shall be based on the total circular mil area of the parallel ungrounded conductors in the raceway or overhead, as indicated in 250.186(A)(1), but not smaller than 1/0 AWG.
(3) Impedance Grounded Neutral Systems
Impedance grounded neutral systems shall be installed in accordance with 250.187.

Related Code Sections

250.24 Wiring and Protection, Grounding Service-Supplied Alternating-Current Systems
A premises wiring system supplied by a grounded ac service shall have a grounding electrode conductor connected to the grounded service conductor ...
(D) Wiring and Protection, Grounding Electrode Conductor
A grounding electrode conductor shall be used to connect the equipment grounding conductors, the service-equipment enclosures, and, where the system ...
(B) Wiring and Protection, Main Bonding Jumper
For a grounded system, an unspliced main bonding jumper shall be used to connect the equipment grounding conductor(s) and the service-disconnect ...