National Electrical Installation Standards

Standards as High as Your Own

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Tuesday, September 19, 2017

Question:

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

A

Answer:

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.

 

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