250.24 (A)(2) Outdoor Transformer

[unsaint34]

The additional grounding connection in 250.24(A)(2) is not an MBJ. It is an additional grounding electrode connection to the grounded service conductor. The grounding electrode must also be outside. It can be made at the transformer (under specific conditions), or more likely at the service disconnecting means (SDM) or the meter, either of which must also be outside. If made at the SDM or meter, the GE is also considered part of the building GES, so it can also qualify say, for example, as the required supplementary electrode for the water pipe electrode. It is not meant to bond the GC and EGC, as the MBJ does.

The reason I thought the additional grounding connection was like a MBJ... Yes, the article reads the grounding connection shall connect the grounded conductor to the electrode, not to the equipment grounding conductor. But, in order to equipment ground the transformer enclosure, I need to bond the enclosure to the grounding connection, essentially making the grounding connection a bonding of all three; grounded, GEC, EGC (enclosure). What am I missing?

 

[unsaint34]

Not the service disconnect. An SBJ, or two, is on an SDS only.

Oops. I should have called it the first disconnect. My mistake.

 

[Smart $]

The reason I thought the additional grounding connection was like a MBJ... Yes, the article reads the grounding connection shall connect the grounded conductor to the electrode, not to the equipment grounding conductor. But, in order to equipment ground the transformer enclosure, I need to bond the enclosure to the grounding connection, essentially making the grounding connection a bonding of all three; grounded, GEC, EGC (enclosure). What am I missing?

Nothing. Just don't call it an MBJ.