Code Change Summary: The rules on sizing a supply-side bonding jumper for parallel conductor installations have been restructured.
In the 2020 NEC®, determining the size of a supply-side bonding jumper (SSBJ) for paralleled conductor installations required a combination of the language (in paragraph form) from Section 250.102(C)(2) as well as language from applicable notes under Table 250.102(C)(1).
In the 2023 NEC® the two existing methods of sizing a SSBJ for parallel conductor installations have been formatted into a numerical list for ease of use and the notes under Table 250.102(C)(1) have been shortened up.
When determining the size of a SSBJ, one must first decide which method to use:
If method 1 above is selected, the SSBJ is sized from Table 250.102(C)(1) based on the largest ungrounded supply conductor in each individual raceway or cable of the parallel set containing the supply conductors.
If method 2 above is selected, the SSBJ is sized from Table 250.102(C)(1) based on the sum of largest ungrounded supply conductor (per phase) in each individual raceway or cable of the parallel set containing the supply conductors. Basically, for phase A, one would add the circular mil area of the supply conductors together and consider it as a single conductor for the application of Table 250.102(C)(1).
For methods 1 and 2 above, if the largest ungrounded supply conductor in the raceway for method 1, or equivalent circular mil area for the ungrounded parallel supply conductors per phase in method 2 exceeds 1100 kcmil copper or 1750 kcmil aluminum, the SSBJ must have an area not less than 12 ½% of the area of the largest ungrounded parallel supply conductors.
Table 250.102(C)(1) Grounded Conductor, Main Bonding Jumper, System Bonding Jumper, and Supply-Side Bonding Jumper for Alternating-Current Systems |
|||
Size of Largest Ungrounded Conductor or Equivalent Area for Parallel Conductors (AWG/kcmil) |
Size of Grounded Conductor or Bonding Jumper* (AWG/kcmil) |
||
Copper |
Aluminum or Copper-Clad Aluminum |
Copper |
Aluminum or Copper-Clad Aluminum |
2 or smaller |
1/0 or smaller |
8 |
6 |
1 or 1/0 | 2/0 or 3/0 | 6 | 4 |
2/0 or 3/0 | 4/0 or 250 | 4 | 2 |
Over 3/0 through 350 |
Over 250 through 500 |
2 | 1/0 |
Over 350 through 600 |
Over 500 through 900 |
1/0 |
3/0 |
Over 600 through 1100 |
Over 900 Through 1750 |
2/0 |
4/0 |
Over 1100 |
Over 1750 |
See Notes 1 and 2. |
Below is a preview of the NEC®. See the actual NEC® text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the 2023 NEC® edition of NFPA 70.
2020 Code Language:
250.102(C)(2) Size for Parallel Conductor Installations in Two or More Raceways or Cables. Where the ungrounded supply conductors are paralleled in two or more raceways or cables, and an individual supply-side bonding jumper is used for bonding these raceways or cables, the size of the supply-side bonding jumper for each raceway or cable shall be selected from Table 250.102(C)(1) based on the size of the ungrounded supply conductors in each raceway or cable. A single supply-side bonding jumper installed for bonding two or more raceways or cables shall be sized in accordance with 250.102(C)(1).
2023 Code Language:
250.102(C)(2) Size for Parallel Conductor Installations in Two or More Raceways or Cables. If the ungrounded supply conductors are connected in parallel in two or more raceways or cables, the supply-side bonding jumper shall be sized in accordance with either of the following:
(1) An individual bonding jumper for each raceway or cable shall be selected from Table 250.102(C)(1) based on the size of the largest ungrounded supply conductor in each raceway or cable.
(2) A single bonding jumper installed for bonding two or more raceways or cables shall be sized in accordance with Table 250.102(C)(1) based on the sum of the circular mil areas of the largest ungrounded conductors from each set connected in parallel in each raceway or cable. The size of the grounded conductor(s) in each raceway or cable shall be based on the largest ungrounded conductor in each raceway or cable, or the sum of the circular mil areas of the largest ungrounded conductors from each set connected in parallel in each raceway or cable.
Refer to the image of NEC Table 250.102(C)(1):
What is the minimum size copper SSBJ permitted if the ungrounded conductors are 500 kcmil copper?
Please register or sign in for electrical continuing education courses. If you were already signed in, your session probably expired, please sign back in. |