517.14 Panelboard Bonding.

In the 2023 NEC, the new exception in 517.14 allows the use of an accessible, securely mounted aluminum or copper busbar for the required panelboard bonding.
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In the 2023 NEC, the new exception in 517.14 allows the use of an accessible, securely mounted aluminum or copper busbar for the required panelboard bonding.

Code Change Summary: A new exception was added to the panelboard bonding requirements.

For several code cycles, terminating equipment grounding conductors or bonding conductors to aluminum and copper busbars not smaller than ¼ inch thick × 2 inches wide has been a permitted practice in several areas of Article 250 in the NEC®. In the 2023 NEC®, Section 517.14 was expanded to permit this practice.

In health care facilities, Section 517.14 requires panelboards to be bonded together when normal and essential branch-circuit panelboards serve the same individual patient care vicinity. The bonding conductor must be an insulated continuous copper conductor not smaller than 10 AWG.

Additionally, if two or more panelboards that serve the same individual patient care vicinity are supplied from separate transfer switches on the essential electrical system, the equipment grounding terminal buses of those panelboards must be connected together with an insulated continuous copper conductor not smaller than 10 AWG. The equipment grounding conductor is permitted to be broken in order to terminate to the equipment grounding terminal bus in each panelboard.

In the 2023 NEC®, the new exception allows the insulated continuous copper bonding conductor not smaller than 10 AWG to be terminated with listed connections to aluminum or copper busbars not smaller than ¼ inch thick × 2 inches wide and of sufficient length to accommodate the number of terminations needed for the required bonding of the panelboards. The busbar must be securely fastened and installed in an accessible location.

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:

The new exception to 517.14 did not exist.

2023 Code Language:

517.14 Panelboard Bonding. The equipment grounding terminal buses of the normal and essential branch-circuit panelboards serving the same individual patient care vicinity shall be connected together with an insulated continuous copper conductor not smaller than 10 AWG. Where two or more panelboards serving the same individual patient care vicinity are served from separate transfer switches on the essential electrical system, the equipment grounding terminal buses of those panelboards shall be connected together with an insulated continuous copper conductor not smaller than 10 AWG. This conductor shall be permitted to be broken in order to terminate on the equipment grounding terminal bus in each panelboard.

Exception: The insulated continuous copper conductor not smaller than 10 AWG shall be permitted to be terminated on listed connections to aluminum or copper busbars not smaller than ¼ inch thick × 2 inches wide and of sufficient length to accommodate the number of terminations necessary for the bonding of the panelboards. The busbar shall be securely fastened and installed in an accessible location.

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517.14 Panelboard Bonding.

Below is a Real Question from our Electrical Continuing Education Courses for Electrical License Renewal:

Based on the 2023 NEC, which of the following is true of the new exception in 517.14?

A: The busbar shall be aluminum.
B: The busbar shall be copper.
C: The busbar shall be at least 12 inches long.
D: The aluminum or copper busbar cannot be smaller than ¼ inch thick × 2 inches wide and of sufficient length to accommodate the number of terminations needed for the required bonding of the panelboards.
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