Separate derived system 480 to 240/120 transformer grounding

[dm9289]

Going thru grounding/bonding videos and i have a question concerning transformers and a common instance in my factory 480VAC Y input Use 2 hots and ground to make 120v/240v single phase system
480VAC feed from MCC 3 wire (no neutral) from breaker.
2 of 3 hots used for transformer primary and ground.
Ground from MCC breaker would be only ground wire.
Run 4 wire to 120v/240v panel from transformer secondary (ground and neutral joined at transformer.

Question In the videos it generally shows at transformer secondary some form of electrode added is this necessary?

 

[ActionDave]

May not be necessary but it's required.

 

[dm9289]

May not be necessary but it's required.

Thats how i seen it from videos.
I'm in a 100-year-old factory cement floors I-beam construction can I use the I-beam as the grounding electrode?

 

[ActionDave]

If it meets the criteria of 250.52 then you can.

 

[dm9289]

If it meets the criteria of 250.52 then you can.

Thanks i have been looking there the beams are bolted to cement so i think .52 may not apply. But 250.68(C)(2) may. It is tough without knowing whats in the concrete

 

[GeorgeB]

Thanks i have been looking there the beams are bolted to cement so i think .52 may not apply. But 250.68(C)(2) may. It is tough without knowing whats in the concrete

Might be a opportunity of proving 25 ohms?

 

[retirede]

Might be a opportunity of proving 25 ohms?

Only relevant in the case of a single ground rod.

 

[Electrical Geek]

Also, the metal underground water pipe. Unless, I am misunderstanding the article.

 

[ActionDave]

Also, the metal underground water pipe. Unless, I am misunderstanding the article.

In a cockeyed sort of way, yes. The water pipe requires a supplemental electrode; if that is a ground rod then you wind up back at the 25 ohm rule