Not all disconnects for a building are required to be in the same distribution panel or enclosure. Many buildings have one common hot gutter that supplies several individual separate disconnect enclosures, grouped in one location.

For this type of installation, one grounding electrode system can be installed and shared by all of the separate service disconnect switches. One way to accomplish this is to use a single grounding electrode conductor, run from the grounding electrode system up to a common busbar of a certain dimension, and then individual GEC taps can be made from the busbar to each individual disconnecting means enclosure.

Section 250.64(D)(1)(3) requires the GEC busbar to be at least ¼ in. thick X 2 in. wide and of sufficient length to accommodate the number of terminations needed for the installation.

Below is a preview of Article 250. 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.

2020 Code Language:

250.64(D)(1) Common Grounding Electrode Conductor and Taps.

(3) Connections to an aluminum or copper busbar not less than 6 mm thick × 50 mm wide (1/4 in. thick × 2 in. wide) and of sufficient length to accommodate the number of terminations necessary for the installation. The busbar shall be securely fastened and shall be installed in an accessible location. Connections shall be made by a listed connector or by the exothermic welding process. If aluminum busbars are used, the installation shall comply with 250.64(A).