National Electrical Installation Standards

Standards as High as Your Own

Tuesday, September 19, 2017


Hello again,

Please help settle a disagreement between a good college of mine and I. I contend that the GEC to a Separately derived system such as a dry type transformer can be terminated to a 4 barrel ground terminal attached to the frame (paint removed) inside the transformer case along with the EG’s and a system bonding jumper from the ground terminal up to the XO terminal. He contends that that 250.64(C) requires the GEC to be continuous without splice to XO, in which I think that it is a connection (250.30(C) not a splice at the Ground terminal. I don’t have a problem with taking the GEC directly to XO but on some transformers there is not enough room on XO for the larger 4 barrel lug.

Thanks, Kelly Wofford



Hey Kelly thanks for your question. For grounded systems the grounding electrode conductor must be connected to the grounded conductor as stated in 250.30(A)(5). Exception 1 allows the grounding electrode conductor to be connected to the equipment grounding terminal bar, of bus, under the conditions provided, - if the system bonding jumper is a wire or busbar. A terminal bar for all grounding and bonding connections must be installed in dry type transformers as stated in 450.10.

So if your "4 barrel ground terminal" is considered the terminal bar by the AHJ, which would be likely, and the system bonding jumper is a wire or busbar - connecting the grounding electrode conductor to that terminal bar is acceptable. Wire type grounding electrode conductors can only be spliced by irreversible compression type connector that are listed to UL 467 or by exothermic welding as stated in 250.64(C)(1) as you indicate. But also as you state a connection of the grounding electrode conductor is not a splice or all the products that have set-screw connections (ground rod clamps, water pipe clamps, etc) would not be allowed for grounding electrode conductor terminations.


ABOUT CQD: NECA’s Code Question of the Day (CQD) is a leading National Electrical Code® forum for NECA and the industry. The CQD generates a lively dialogue and relative practical and Code-based responses to an ever-increasing and interactive audience.

IMPORTANT NOTICE: All answers are based on the latest edition of the National Electrical Code®, unless the question requests a response based on a specific edition. This correspondence is not a formal interpretation of the NEC®. Any responses expressed to the questions are opinions and do not necessarily represent the official position of NECA, NFPA, or any technical committee. In addition, this correspondence is neither intended, nor should it be relied upon, to provide professional consultation or services.

ABOUT CHARLIE: Charles M. Trout, better known as Charlie, was a nationally known NEC® expert and author. He served on several NEC® technical committees and is past chairman of CMP-12. In 2006 Charlie was awarded the prestigious Coggeshall Award for outstanding contributions to the electrical contracting industry, codes and standards development, and technical training. Charlie was also a member of NECA’s Academy of Electrical Contracting. Charlie’s experienced team of industry experts keep the CQD dialogue and discussions active and informative in the spirit of the man himself, as he wanted.

NECA STANDARDS: NECA publishes the National Electrical Installation Standards™ (NEIS™), a series of ANSI-approved performance and quality standards for electrical construction. Visit for more information. NEISÔ can be purchased in three formats: as paper books, on CD, or as electronic downloads.

NECA SAFETY PRODUCTS: NECA publishes valuable electrical safety books and CDs for the industry. Visit to view or purchase NECA safety products.

 CONTACT US: To submit a Code question, subscribe, or unsubscribe from this list, please e-mail: