300.3(B)(1) Paralleled Installations.
Code Change Summary: Revised code language on making connections, taps or extensions from paralleled conductors.
NEC 310.10(G) provides rules on installing conductors in parallel but doesn’t provide any insight on making a tap to a parallel set of conductors.
In Section 300.3(B)(1) of the 2020 NEC®, a public input (code change proposal) was accepted to address taps, connections, or extensions made from paralleled conductors. The revised code language makes it clear that a tap, connection, or extension made from paralleled conductors must connect to ALL conductors of the paralleled set.
The intent of the code change is to ensure that the conductors that are connected in parallel carry an equal amount of current which is critical since none of the individual conductors in the parallel set is usually capable of carrying all of the current permitted by the overcurrent device.
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 2020 NEC® edition of NFPA 70.
2017 Code Language:
300.3(B)(1) Paralleled Installations. Conductors shall be permitted to be run in parallel in accordance with the provisions of 310.10(H). The requirement to run all circuit conductors within the same raceway, auxiliary gutter, cable tray, trench, cable, or cord shall apply separately to each portion of the paralleled installation, and the equipment grounding conductors shall comply with the provisions of 250.122. Parallel runs in cable tray shall comply with the provisions of 392.20(C).
2020 Code Language:
300.3(B)(1) Paralleled Installations. Conductors shall be permitted to be run in parallel in accordance with the provisions of 310.10(G). The requirement to run all circuit conductors within the same raceway, auxiliary gutter, cable tray, trench, cable, or cord shall apply separately to each portion of the paralleled installation, and the equipment grounding conductors shall comply with 250.122. Connections, taps, or extensions made from paralleled conductors shall connect to all conductors of the paralleled set, grounded and ungrounded, as applicable. Parallel runs in cable trays shall comply with 392.20(C).